Method and apparatus for testing wells

Abstract

A method and apparatus for testing offshore wells where variations in well annulus pressure are utilized to control the valving operation of a testing tool and entrap a formation sample. A confined body of pressurized fluid positoned in a testing string is utilized to predetermine the annulus pressure changes which will effect said valving and sample entrapping operations.

What is claimed is:  .[.1. A method of testing a formation intersected by a well bore, said method comprising: 
     
        formation..]. 3. A method of testing a submerged formation from an offshore test site, said method comprising: disposing a test string including tester valve controlled conduit means between a floating vessel and a submerged formation;   maintaining pressure in a body of liquid in a submerged well bore, disposed adjacent said conduit means, at a relatively low level while maintaining said body of liquid isolated .[.form.]. .Iadd.from .Iaddend.a submerged formation to be tested;   in response to said relatively low level of pressure in said body of liquid, maintaining a flow path leading from said formation through said conduit means in said well bore in a closed condition;   increasing the pressure of said liquid body while isolating said increase in pressure of said liquid body from said formation;   in response to said increase in pressure, permitting fluid to flow from said formation through said conduit means;   further .[.decreasing.]. .Iadd.increasing .Iaddend.the pressure of liquid in said liquid body while isolating said further .[.decrease.]. .Iadd.increase .Iaddend.in pressure from said formation;   in response to said further .[.decrease.]. .Iadd.increase .Iaddend.of pressure of said liquid body, entrapping within said conduit means a sample of fluid from said formation;   maintaining a confined body of pressurized gas in said conduit means operable to determine the pressure level in said liquid body operable to permit said liquid to flow from said formation through said conduit means; and   maintaining yieldable means in said conduit means operable to determine the   
     
     
        pressure level in said liquid body operable to cause said entrapping. 4. A method as described in claim 3 further comprising: effecting said testing while concurrently substantially preventing wave action induced forces from being transmitted through said test string from   
     
     
        said floating work station to said conduit means. 5. A method of testing a formation, intersected by a well bore site, said method comprising: providing a well testing assembly including: conduit means communicating with a formation to be tested, with said conduit means being disposed in a well bore and selectively removable therefrom,   wall means encircling at least a portion of said conduit means, and   selectively releasable sealing means extending between said conduit means and said wall means and cooperating with said conduit means and said wall means to provide a well annulus isolated from the interior of said conduit means;     regulating flow from said formation through said conduit means with an assembly including: first, valve seat means carried by a wall portion of said conduit means,   second, valve seat means carried by another interior wall portion of said conduit means, and spaced longitudinally of and above said first valve seat means,   slidable sample chamber side wall means mounted on said first and second valve seat means for sliding movement longitudinally of said conduit means,   first valve means carried by a lower portion of said slidable sample chamber side wall means and disposed in valving cooperation with said first valve seat means,   second valve means carried by an upper portion of said slidable sample chamber side wall means and disposed in valving cooperation with said second valve seat means,   formation fluid inlet passage means operable to transmit formation fluid from said formation to the interior of said slidable sample chamber side wall means under valving control of said first sleeve valve means,   formation fluid output passage means operable to transmit formation fluid from the interior of said slidable sample chamber side wall means to the interior of said conduit means under valving control of said second sleeve valve means,   said first and second sleeve valve means being concurrently operable in response to movement of said slidable sample chamber side wall means,   said first and second sleeve valve means being sequentially movable from a first position closing said inlet and outlet passage means, to   a second position opening said inlet and outlet passage means, and to   a third position closing said inlet and outlet passage means;       providing a formation sample trapping chamber means including: wall means cooperating with said first and second valve seat means and said slidable sample chamber side wall means to define a sample receiving cavity;     providing formation testing actuating means including: pressurizing means selectively operable to increase the pressure of fluid in said well annulus, with said sealing means isolating said well annulus from said formation,   piston means carried by said sample chamber side wall means,   cylinder means defined by a portion of said conduit means with said piston means being slidably mounted therein,   first expansible and contractible cavity means included in said cylinder means and containing a body of expansible and contractible pressurized fluid yieldably biasing said piston means and slidable sample chamber side wall means in one direction,   second expansible and contractible cavity means included in said cylinder means operable to receive formation fluid to bias said piston means in another direction opposite to said one direction,   communicating means providing pressure-change transmitting fluid communication between said second expansible and contractible cavity means and said well annulus; and     testing said formation by: imparting the pressure of said pressurized fluid to said piston means to urge said slidable sample chamber side walls means in said one direction and hold said first and second sleeve valve means in said first, position to prevent a flow of formation fluid through said sample trapping chamber means from said formation, while maintaining said relatively low pressure level in said well annulus,   operating said pressurizing means to increase the pressure of fluid in said well annulus, with said increase in pressure being operable to provide said relatively intermediate pressure in said well annulus and effect movement of said sample chamber side wall means in said opposite direction and move said first and second valve means from said first position to said second position to permit a flow of fluid consecutively through said inlet passage means, interior of said sample trapping chamber means, and outlet passage means, and   operating said pressurizing means to provide said relatively high pressure level in said well annulus to cause said first and second valve means to move in said opposite direction from said second position to said third position and entrap a sample of formation fluid in said sample trapping     
     
     
        chamber means. 6. A method of testing a formation as described in claim 5, said method further comprising: providing valve latching means including: socket means carried by said conduit means above said slidable sample chamber side wall means, and   1atching means carried by said slidable sample chamber side wall means and operable to releasably latch said sample chamber side wall means in said socket means when said first and second valve means are moved to said third position;     providing venting valve means in said conduit means below said first valve means and operable to vent pressurized fluid from the interior of said conduit means to the exterior thereof in response to a decrease in pressure of fluid adjacent the exterior of said conduit means;   providing yieldable restraining means carried by said sample chamber side wall means, said restraining means being operable to yieldably prevent movement of said first and second sleeve valve means from said second position to said said third position, said restraining means being further operable to position said first and second sleeve valve means at said first position in response to a relatively low pressure level in said well annulus,   at said second position in response to a relatively intermediate pressure level in said well annulus, and   at said third position in response to a relatively high pressure level in said well annulus;     providing yieldable movement impedance means operable to yieldably impede initial upward movement of said piston means in said cylinder means and permit relatively unimpeded downward movement of said piston means in said cylinder means,   operating said impedance means during said movement of said first and second valve means from said first position to said second position to impede movement of said first and second valve means,   operating said pressurizing means to decrease the pressure of fluid in said well annulus and provide said relatively low pressure therein and effect movement of said first and second valve means in said one direction from said second position to said first position,   operating said impedance means during said movement of said first and second valve means from said second position to said first position to permit relatively unimpeded downward movement of said first and second valve means,   operating said valve latching means to secure said first and second valve means in said third position; and   after said testing of said formation, releasing said sealing means from said wall means and permitting said venting valve means to vent the interior of said conduit means to the well bore interior in response to raising of said conduit means upwardly through said well bore and a reduction in the hydrostatic pressure of fluid in said well bore adjacent   
     
     
        said venting valve means. 7. A method of testing a submerged formation from an offshore test site, said method comprising: providing a well testing assembly including: tubular conduit means communicating with a formation to be tested with said conduit means being disposed in a well bore and selectively removable therefrom to a floating work station,   wall means encircling at least a portion of said conduit means, and   selectively releasable sealing means extending between said conduit means and said wall means and cooperating with said conduit means and said wall means to provide a well annulus isolated from the interior of said conduit means;     regulating flow from said formation through said conduit means with an assembly including: first, generally tubular valve seat means carried by and spaced inwardly from an interior wall portion of said conduit means and mounted concentrically therewith,   second, generally tubular valve seat means carried by and spaced inwardly from another interior wall portion of said conduit means, mounted concentrically therewith, and spaced longitudinally of and above said first valve seat means,   slidable sample chamber side wall means mounted on said first and second valve seat means for sliding movement longitudinally of said conduit means,   first sleeve valve means carried by a lower portion of said slidable sample chamber side wall means and disposed in valving cooperating with said first valve seat means,   second sleeve valve means carried by an upper portion of said slidable sample chamber side wall means and disposed in valving cooperation with said second valve seat means,   formation fluid inlet passage means carried by said first valve seat means, and operable to transmit formation fluid from said formation to the interior of said slidable sample chamber side wall means under valving control of said first sleeve valve means,   formation fluid outlet passage means carried by said first valve seat means, and operable to transmit formation fluid from the interior of said slidable sample chamber side wall means to the interior of said conduit means under valving control of said second sleeve valve means,   said first and second sleeve valve means being concurrently operable in response to movement of said slidable sample chamber side wall means, said first and second sleeve valve means being sequentially movable from a first, lower position closing said inlet and outlet passage means, to   a second, intermediate position above said first position opening said inlet and outlet passage means, and to   a third, upper position above said second position closing said inlet and outlet passage means;       providing a formation sample trapping chamber means including: first barrier means closing a lower portion of said first valve seat means,   second barrier means closing an upper portion of said second valve seat means,   said first and second barrier means cooperating with said first and second valve seat means to provide sample entrapping closures at upper and lower ends, respectively, of said slidable sample chamber side wall means; .Iadd.     providing yieldable restraining means carried by said sample chamber side wall means, said restraining means being operable to yieldably prevent movement of said first and second sleeve valve means from said second position to said third position, .Iaddend.   providing formation testing actuating means including: pump means selectively operable from said floating work station to increase the pressure of fluid in said well annulus, with said sealing means isolating said well annulus from said formation,   annular piston means carried on the exterior of said sample chamber side wall means and mounted coaxially thereof,   cylinder means defined by a portion of said conduit means with said piston means being slidably mounted therein,   first expansible and contractible cavity means included in said cylinder means above said piston means and containing a body of expansible and contractible pressurized fluid yieldably biasing said piston means and slidable sample chamber side wall means downwardly,   second expansible and contractible cavity means included in said cylinder means below said piston means,   communicating means provide pressure-change transmitting fluid communication between said second expansible and contractible cavity means and said well annulus;     testing said formation by: imparting the pressure of said pressurized fluid to said piston means to urge said slidable sample chamber side wall means downwardly and hold said first and second sleeve valve means in said first, lower position to prevent a flow of formation fluid through said sample trapping chamber means from said formation, while maintaining .[.said.]. .Iadd.a .Iaddend.relatively low pressure level in said well annulus,   operating said pump means at said floating work station to increase the pressure of fluid in said well annulus, with said increase in pressure being operable to provide .[.said.]. .Iadd.a .Iaddend.relatively intermediate pressure in said well annulus and effect upward movement of said sample chamber side wall means and move said first and second valve means from said first lower position to said second, intermediate position to permit a flow of fluid consecutively through said inlet passage means, interior of said sample trapping chamber means, and outlet passage means,   operating said pump means at said floating work station to provide .[.said.]. .Iadd.a .Iaddend.relatively high pressure level in said well annulus to cause said restraining means to yield, and move said first and second valve means from said second intermediate position to said third, upper position and entrap a sample of formation fluid in said sample trapping chamber means,     after said testing of said formation, releasing said sealing means from said wall means, and raising said conduit means to said floating work station; and   effecting said testing while concurrently substantially preventing wave action induced forces from being transmitted from said floating work   
     
     
        station to said conduit means. 8. A method of testing a submerged formation from an offshore test site, said method comprising: providing a well testing assembly including: tubular conduit means communicating with a formation to be tested with said conduit means being disposed in a well bore and selectively removable therefrom to a floating work station,   wall means encircling at least a portion of said conduit means, and   selectively releasable sealing means extending between said conduit means and said wall means and cooperating with said conduit means and said wall means to provide a well annulus isolated from the interior of said conduit means;     regulating flow from said formation through said conduit means with an assembly including: first, generally tubular valve seat means carried by and spaced inwardly from an interior wall portion of said conduit means and mounted concentrically therewith,   second, generally tubular valve seat means carried by and spaced inwardly from another interior wall portion of said conduit means, mounted concentrically therewith, and spaced longitudinally of and above said first valve seat means,   slidable sample chamber side wall means mounted on said first and second valve seat means for sliding movement longitudinally of said conduit means,   first sleeve valve means carried by a lower portion of said slidable sample chamber side wall means and disposed in valving cooperation with said first valve seat means,   second sleeve valve means carried by an upper portion of said slidable sample chamber side wall means and disposed in valving cooperation with said second valve seat means,   formation fluid inlet passage means carried by said first valve seat means, and operable to transmit formation fluid from said formation to the interior of said slidable sample chamber side wall means under valving control of said first sleeve valve means,   formation fluid outlet passage means carried by said first valve seat means, and operable to transmit formation fluid from the interior of said slidable sample chamber side wall means to the interior of said conduit means under valving control of said second sleeve valve means,   said first and second sleeve valve means being concurrently operable in response to movement of said slidable sample chamber side wall means, said first and second sleeve valve means being sequentially movable from a first, lower position closing said inlet and outlet passage means, to   a second, intermediate position above said first position opening said inlet and outlet passage means, and to   a third, upper position above said second position closing said inlet and outlet passage means,     first valve shielding means defined by a first wall portion of said conduit means, spaced outwardly of said inlet passage means and first valve seat means, and cooperating with said first valve seat means to define a first annular passage leading to said inlet passage means,     second valve shielding means defined by a second wall portion of said conduit means, spaced outwardly of said outlet passage means and second valve seat means and cooperating with said second valve seat means to define a second annular passage leading from said outlet passage means;       providing a formation sample trapping chamber means including: first barrier means closing a lower portion of said first valve seat means,   second barrier means closing an upper portion of said second valve seat means,   said first and second barrier means cooperating with said first and second valve seat means to provide sample entrapping closures at upper and lower ends, respectively, of said slidable sample chamber side wall means,   first, passage means carried by said first barrier means and disposed axially thereof,   first plug valve means valvingly mounted in said first passage means,   second, passage means carried by said second barrier means and disposed axially thereof and   second plug valve means valvingly mounted in said second passage means,   said first valve shielding means being removable from said conduit means to provide access to said first plug valve means, and   said second valve shielding means being removable from said conduit means to provide access to said second plug valve means;     providing formation testing actuating means including: pump means selectively operable from said floating work station to increase the pressure of fluid in said well annulus, with said sealing means isolating said well annulus from said formation,   annular piston means carried on the exterior of said sample chamber side wall means and mounted coaxially thereof,   cylinder means defined by a portion of said conduit means with said piston means being slidably mounted therein,   first expansible and contractible cavity means included in said cylinder means above said piston means and containing a body of expansible and contractible pressurized nitrogen yieldably biasing said piston means and slidable sample chamber side wall means downwardly,   second expansible and contractible cavity means included in said cylinder means below said piston means,   communicating means provide pressure-change transmitting fluid communication between said second expansible and contractible cavity means and said well annulus;     providing valve latching means including: first latching means carried by said sample trapping chamber means, and   second latching means carried by said slidable sample chamber side wall means and operable to engage said first latching means and latch said sample chamber side wall means with said sample trapping chamber means and secure said first and second sleeve valve means in said third, upper position;     providing venting valve means in said conduit means below said first valve means and operable to vent pressurized fluid from the interior of said conduit means to the exterior thereof in response to a decrease in pressure of fluid adjacent the exterior of said conduit means;   providing yieldable restraining means carried by said sample chamber side wall means, said restraining means being operable to yieldably prevent movement of said first and second sleeve valve means from said second, intermediate position to said third upper position, said restraining means being further operable to position said  first and second sleeve valve means at said first, lower position in response to a relatively low pressure level in said well annulus,   at said second, intermediate position in response to a relatively intermediate pressure level in said well annulus, and   at said third, upper position in response to a relatively high pressure level in said well annulus;     providing yieldable movement impedance means operable to relatively impede initial upward movement of said piston means in said cylinder means and permit relatively unimpeded downward movement of said piston means in said cylinder means, said impedance means including disabling means operable to substantially vitiate the movement impeding operation of said impedance means after said yieldable restraining means has yielded to permit said first and second sleeve valve means to move from said second, intermediate position toward said third, upper position;     supporting said conduit means at said floating work station while providing: collapsible and extensible coupling means between said conduit means and said floating work station; and     testing said formation by: imparting the pressure of said pressurized nitrogen to said piston means to urge said slidable sample chamber side wall means downwardly and hold said first and second sleeve valve means in said first, lower position to prevent a flow of formation fluid through said sample trapping chamber means from said formation, while maintaining said relatively low pressure level in said well annulus,   operating said pump means at said floating work station to increase the pressure of fluid in said well annulus, with said increase in pressure being operable to provide said relatively intermediate pressure in said well annulus and effect upward movement of said sample chamber side wall means and move said first and second valve means from said first lower position to said second, intermediate position to permit a flow of fluid consecutively through said inlet passage means, interior of said sample trapping chamber means, and outlet passage means, with said fluid approaching said sample trapping chamber means through said first annular passage and leaving said sample trapping chamber means through said second annular passage,   operating said impedance means during said movement of said first and second valve means from said first lower position to said second intermediate position to impede movement of said first and second valve means,   operating said pump means at said floating work station to decrease the pressure of fluid in said well annulus and provide said relatively low pressure therein and effect downward movement of said first and second valve means from said second, intermediate position to said first, lower position,   operating said impedance means during said downward movement of said first and second valve means from said second, intermediate position to said first lower position to permit relatively unimpeded downward moement of said first and second valve means,   operating said pump means at said floating work station to provide said relatively high pressure level in said well annulus to cause said restraining means to yield, and move said first and second valve means from said second intermediate position to said third, upper position and entrap a sample of formation fluid in said sample trapping chamber means,   operating said disabling means during said movement of said first and second valve means from said second, intermediate position to said third, upper position to substantially vitiate the movement impeding operation of said impedance means,   operating said valve latching means to secure said first and second valve means in said third, upper position;     after said testing of said formation, releasing said seating means from said wall means, raising said conduit means to said floating work station, and permitting said venting valve means to vent the interior of said conduit means to the well bore interior in response to the raising of said conduit means upwardly through said well bore and a reduction in the hydrostatic pressure of fluid in said well bore adjacent said venting valve means;   removing said first and second valve shielding means from said conduit means to provide substantially unobstructed access to said first and second plug valve means; and   operating at least one of said first and second plug valve means to remove   
     
     
        formation fluid from said formation sample trapping chamber means. 9. A method as described in claim 8 further comprising: providing first relatively large, fluid reaction surface means carried by said annular piston means and disposed in fluid communicating relation with said expansible and contractible cavity   providing second relatively small, fluid reaction surface means carried by said annular piston means and disposed in fluid communicating relation with said second expansible and contractible cavity means;   inducing movement of said annular piston means in response to fluid forces   
     
     
        generated within said first and second cavity means. 10. A method as described in claim 9 further comprising: effecting said testing while concurrently, substantially preventing wave action induced forces from being transmitted from said floating work station to said conduit means.  .[.11. Apparatus for testing a formation intersected by a well bore, said apparatus comprising:   means for maintaining pressure in a body of fluid in a well bore, disposed adjacent a conduit means, at one level while maintaining said body of fluid isolated from a submerged formation to be tested and the interior of said conduit means;   means operable in response to said one level of pressure in said body of fluid, to maintain a flow path leading from said formation through said conduit means in said well bore in a closed condition;   means for changing the pressure of said fluid body while isolating said change in pressure of said fluid body from said formation;   means operable in response to said change in pressure, to permit fluid to flow from said formation through said conduit means;   means for further changing the pressure of fluid in said fluid body while isolating said further change in pressure from said formation and the interior of said conduit means; and   means operable in response to said further change of pressure of said fluid body, to entrap within said conduit means a sample of fluid from said formation..]. .[.12. Apparatus for testing a submerged formation from an comprising: test site, said apparatus comprising:   means for maintaining pressure in a body of fluid in a submerged well bore, disposed adjacent a conduit means, at a relatively low level while maintaining said body of fluid isolated from a submerged formation to be tested;   means operable in response to said relatively low level of pressure in said body of fluid, to maintain a flow path leading from said formation through said conduit means in said well bore in a closed condition;   means for increasing the pressure of said fluid body while isolating said increase in pressure of said fluid body from said formation;   means operable in response to said increase in pressure to permit fluid to flow from said formation through said conduit means;   means for further decreasing the pressure of fluid in said fluid body while isolating said further decrease in pressure from said formation; and   means operable in response to said further decrease of pressure of said fluid body, to entrap within said conduit means a sample of fluid from   
     
     
        said formation..]. 13. Apparatus for testing a submerged formation from an offshore test site, said apparatus comprising: means for disposing a test string including tester valve controlled conduit means between a floating vessel and a submerged formation;   means for maintaining pressure in a body of liquid in a submerged well bore, disposed adjacent said conduit means, at a relatively low level while maintaining said body of liquid isolated from a submerged formation to be tested;   means operable in response to said relatively low level of pressure in said body of .[.liquie.]. .Iadd.liquid.Iaddend., to maintain a flow path leading from said formation through said conduit means in said well bore is a closed condition;   means for increasing the pressure of said liquid body while isolating said increase in pressure of said liquid body from said formation;   means operable in response to said increase in pressure, to permit fluid to flow from said formation through said conduit means;   means for further .[.decreasing.]. .Iadd.increasing .Iaddend.the pressure of liquid in said liquid body while isolating said further .[.decrease.]. .Iadd.increase .Iaddend.in pressure from said formation;   means operable in response to said further .[.decrease.]. .Iadd.increase .Iaddend.of pressure of said liquid body, to entrap within said conduit means of sample of fluid from said formation;   means providing and maintaining a confined body of pressurized gas in said conduit means, with said body being operable to determine the pressure level in said liquid body operable to permit said liquid to flow from said formation through said conduit means;   yieldable means in said conduit means operable to determine the pressure   
     
     
        level in said liquid body operable to cause said entrapping. 14. Apparatus as described in claim 13 further comprising: means for effecting said testing whle concurrently substantially preventing wave action induced forces from being transmitted through said test string   
     
     
        form said floating work station to said conduit means. 15. Apparatus for testing a formation, intersected by a well bore site, said apparatus comprising: a well testing assembly including conduit means communicating with a formation to be tested, with said conduit means being disposed in a well bore and selectively removable therefrom,   wall means encircling at least a portion of said conduit means, and   selectively releasable sealing means extending between said conduit means and said wall means and cooperating with said conduit means and said wall means to provide a well annulus isolated from the interior of said conduit means;     means for regulating flow from said formation through said conduit means and including first, valve seat means carried by a wall portion of said conduit means,   second, valve seat means carried by another interior wall portion of said conduit means, and spaced longitudinally of and above said first valve seat means,   slidable sample chamber side wall means mounted on said first and second valve seat means for sliding movement longitudinally of said conduit means,   first valve means carried by a lower portion of said slidable sample chamber side wall means and disposed in valving cooperation with said first valve seat means,   second valve means carried by an upper portion of said slidable sample chamber side wall means and disposed in valving cooperation with said second valve seat means,   formation fluid inlet passage means operable to transmit formation fluid from said formation to the interior of said slidable sample chamber side wall means under valving control of said first sleeve valve means,   formation fluid outlet passage means operable to transmit formation fluid from the interior of said slidable sample chamber side wall means to the interior of said conduit means under valving control of said second sleeve valve means,   said first and second sleeve valve means being concurrently operable in response to movement of said slidable sample chamber side wall means,   said first and second sleeve valve means being sequentially movable from a first position closing said inlet and outlet passage means, to   a second position opening said inlet and outlet passage means, and to   a third position closing said inlet and outlet passage means;       a formation sample trapping chamber means including: wall means cooperating with said first and second valve seat means and said slidable sample chamber side wall means to define a sample receiving cavity; and     formation testing actuating means including pressurizing means selectively operable to increase the pressure of fluid in said well annulus, with said sealing means isolating said well annulus from said formation,   piston means carried by said sample chamber side wall means,   cylinder means defined by a portion of said conduit means with said piston means being slidably mounted therein,   first expansible and contractible cavity means included in said cylinder means and containing a body of expansible and contractible pressurized fluid yieldably biasing said piston means and slidable sample chamber side wall means in one direction,   second expansible and contractible cavity means included in said cylinder means operable to receive formation fluid to bias said piston means in another direction opposite to said one direction,   communicating means providing pressure-change transmitting fluid communication between said second expansible and contractible cavity means     
     
     
        and said well annulus. 16. Apparatus for testing a formation as described in claim 15, said apparatus further comprising: valve latching means including: socket means carried by said conduit means above said slidable sample chamber side wall means, and   1atching means carried by said slidable sample chamber side wall means and operable to releasably latch said sample chamber side wall means in said socket means when said first and second valve means are moved to said third position;     venting valve means in said conduit means below said first valve means and operable to vent pressurized fluid from the interior of said conduit means to the exterior thereof in response to a decrease in pressure of fluid adjacent the exterior of said conduit means;   yieldable restraining means carried by said sample chamber side wall means, said restraining means being operable to yieldably prevent movement of said first and second sleeve valve means from said second position to said third position, said restraining means being further operable to position said first and second sleeve valve means at said first position in response to a relatively low pressure level in said well annulus,   at said second position in response to a relatively intermediate pressure level in said well annulus, and   at said third position in response to a relatively high pressure level in said well annulus; and     yieldable movement impedance means operable to yieldably impede initial upward movement of said piston means in said cylinder means and permit relatively unimpeded downward movement of said piston means in said   
     
     
        cylinder means. 17. Apparatus for testing a submerged formation from an offshore test site, said apparatus comprising: a well testing assembly including tubular conduit means communicating with a formation to be tested with said conduit means being disposed in a well bore and selectively removable therefrom to a floating work station,   wall means encircling at least a portion of said conduit means, and   selectively releasable sealing means extending between said conduit means and said wall means and cooperating with said conduit means and said wall means to provide a well annulus isolated from the interior of said conduit means;     means for regulating flow from said formation through said conduit means and including first, generally tubular valve seat means carried by and spaced inwardly from an interior wall portion of said conduit means and mounted concentrically therewith,   second, generally tubular valve seat means carried by and spaced inwardly from another interior wall portion of said conduit means, mounted concentrically therewith, and spaced longitudinally of and above said first valve seat means,   slidable sample chamber side wall means mounted on said first and second valve seat means for sliding movement longitudinally of said conduit means,   first sleeve valve means carried by a lower portion of said slidable sample chamber side wall means and disposed in valving .[.cooperating.]. .Iadd.cooperation .Iaddend.with said first valve seat means,   second sleeve valve means carried by an upper portion of said slidable sample chamber side wall means and disposed in valving cooperating with said second valve seat means,   formation fluid inlet passage means carried by said first valve seat means, and operable to transmit formation fluid from said formation to the interior of said slidable sample chamber side wall means under valving control of said first sleeve valve means,   formation fluid outlet passage means carried by said first valve seat means, and operable to transmit formation fluid from the interior of said slidable sample chamber side wall means to the interior of said conduit means under valving control of said second sleeve valve means,   said first and second sleeve valve means being concurrently operable in response to movement of said slidable sample chamber side wall means, said first and second sleeve valve means being sequentially movable from a first, lower position closing said inlet and outlet passage means, to   a second, intermediate position above said first position opening said inlet and outlet passage means, and to   a third, upper position above said second position closing said inlet and outlet passage means;       a formation sample trapping chamber means including first barrier means closing a lower portion of said first valve seat means,   second barrier means closing an upper portion of said second valve seat means,   said first and second barrier means cooperating with said first and second valve seat means to provide sample entrapping closures at upper and lower ends, respectively, of said slidable sample chamber side wall means; and     formation testing actuating means including pump means selectively operable from said floating work station to increase the pressure of fluid in said well annulus, with said sealing means isolating said well annulus from said formation,   annular piston means carried on the exterior of said sample chamber side wall means and mounted coaxially thereof,   cylinder means defined by a portion of said conduit means with said piston means being slidably mounted therein,   first expansible and contractible cavity means included in said cylinder means above said piston means and containing a body of expansible and contractible pressurized fluid yieldably biasing said piston means and slidable sample chamber side wall means downwardly,   second expansible and contractible cavity means included in said cylinder means below said piston means, and   communicating means provide pressure-change transmitting fluid communication between said second expansible and contractible cavity means     
     
     
        and said well annulus. 18. Apparatus for testing a submerged formation from an offshore test site, said apparatus comprising: a well testing assembly including tubular conduit means communicating with a formation to be tested with said conduit means being disposed in a well bore and selectively removable therefrom to a floating work station,   wall means encircling at least a portion of said conduit means, and   selectively releasable sealing means extending between said conduit means and said wall means and cooperating with said conduit means and said wall means to provide a well annulus isolated from the interior of said conduit means;     means for regulating flow from said formation through said conduit means and including first, generally tubular valve seat means carried by and spaced inwardly from an interior wall portion of said conduit means and mounted concentrically therewith,   second, generally tubular valve seat means carried by and spaced inwardly from another interior wall portion of said conduit means, mounted concentrically therewith, and spaced longitudinally of and above said first valve seat means,   slidable sample chamber side wall means mounted on said first and second valve seat means for sliding movement longitudinally of said conduit means,   first sleeve valve means carried by a lower portion of said slidable sample chamber side wall means and disposed in valving cooperation with said first valve seat means,   second sleeve valve means carried by an upper portion of said slidable sample chamber side wall means and disposed in valving cooperation with said second valve seat means,   formation fluid inlet passage means carried by said first valve seat means, and operable to transmit formation fluid from said formation to the interior of said slidable sample chamber side wall means under valving control of said first sleeve valve means,   formation fluid outlet passage means carried by said first valve seat means, and operable to transmit formation fluid from the interior of said slidable sample chamber side wall means to the interior of said conduit means under valving control of said second sleeve valve means,   said first and second sleeve valve means being concurrently operable in response to movement of said slidable sample chamber side wall means, said first and second sleeve valve means being sequentially movable from a first, lower position closing said inlet and outlet passage means, to   a second, intermediate position above said first position opening said inlet and outlet passage means, and to   a third, upper position above said second position closing said inlet and outlet passage means,     first valve shielding means defined by a first wall portion of said conduit means, spaced outwardly of said inlet passage means and first valve seat means, and cooperating with said first valve seat means to define a first annular passage leading to said inlet passage means,     second valve shielding means defined by a second wall portion of said conduit means, spaced outwardly of said outlet passage means and second valve seat means and cooperating with said second valve seat means to define a second annular passage leading from said outlet passage means;       a formation sample trapping chamber means including first barrier means closing a lower portion of said first valve seat means,   second barrier means closing an upper portion of said second valve seat means,   said first and second barrier means cooperating with said first and second valve seat means to provide sample entrapping closures at upper and lower ends, respectively, of said slidable sample chamber side wall means,   first, passage means carried by said first barrier means and disposed axially thereof,   first plug valve means valvingly mounted in said first passage means,   second, passage means carried by said second barrier means and disposed axially thereof, and   second plug valve means valvingly mounted in said second passage means,   said first valve shielding means being removable from said conduit means to provide access to said first plug valve means, and   said second valve shielding means being removable from said conduit means to provide access to said second plug valve means;     formation testing actuating means including pump means selectively operable from said floating work station to increase the pressure of fluid in said well annulus, with said sealing means isolating said well annulus from said formation,   annular piston means carried on the exterior of said sample chamber side wall means and mounted coaxially thereof,   cylinder means defined by a portion of said conduit means with said piston means being slidably mounted therein,   first expansible and contractible cavity means included in said cylinder means above said piston means and containing a body of expansible and contractible pressurized nitrogen yieldably biasing said piston means and slidable sample chamber side wall means downwardly,   second expansible and contractible cavity means included in said cylinder means below said piston means,   communicating means provide pressure-change transmitting fluid communication between said second expansible and contractible cavity means and said well annulus;     valve latching means including first latching means carried by said sample trapping chamber means, and   second latching means carried by said slidable sample chamber side wall means and operable to engage said first latching means and latch said sample chamber side wall means with said sample trapping chamber means and secure said first and second sleeve valve means in said third, upper position;     venting valve means in said conduit means below said first valve means and operable to vent pressurized fluid from the interior of said conduit means to the exterior thereof in response to a decrease in pressure of fluid adjacent the exterior of said conduit means;   yieldable restraining means carried by said sample chamber side wall means, said restraining means being operable to yieldably prevent movement of said first and second sleeve valve means from said second, intermediate position to said third upper position, said restraining means being further operable to position said first and second sleeve valve means at said first, lower position in response to a relatively low pressure level in said well annulus,   at said second, intermediate position in response to a relatively intermediate pressure level in said well annulus, and   at said third, upper position in response to a relatively high pressure level in said well annulus;     yieldable movement impedance means operable to relatively impede initial upward movement of said piston means in said cylinder means and permit relatively unimpeded downward movement of said piston means in said cylinder means, said impedance means including disabling means operable to substantially vitiate the movement impeding operation of said impedance means after said yield-able restraining means has yielded to per-mit said first and second sleeve valve means to move from said second, intermediate position toward said third, upper position; and     collapsible and extensible coupling means disposed between said conduit   
     
     
        means and said floating work station. 19. Apparatus as described in claim 18 further comprising: first, relatively large, fluid reaction surface means carried by said annular piston means and disposed in fluid communicating relation with said first expansible and contractible cavity means; and   second, relatively small, fluid reaction surface means carried by said annular piston means and disposed in fluid communicating relation with   
     
     
        said second expansible and contractible cavity means. 20. Apparatus as described in claim 19 further comprising: submerged means operable to substantially prevent wave action induced forces from being transmitted from said floating work station to said conduit means. .Iadd. 21. A method of testing a formation intersected by a well bore, said method comprising:   maintaining pressure in a body of fluid in a well bore, disposed adjacent a conduit means, at one level while maintaining said body of fluid isolated from a submerged formation to be tested and the interior of said conduit means;   in response to said one level of pressure in said body of fluid, maintaining a flow path leading from said formation through said conduit means in said well bore in a closed condition;   changing the pressure of said fluid body while isolating said change in pressure of said fluid body from said formation;   in response to said change in pressure, permitting fluid flow from said formation through said conduit means;   further changing the pressure of fluid in said fluid body while isolating said further change in pressure from said formation and the interior of said conduit means; and   in response to said further change of pressure of said fluid body, entrapping within a closed sample chamber provided in said conduit means a sample of fluid from said formation, and   securing said sample chamber in said sample entrapping closed condition and preventing any subsequent opening thereof in response to subsequent pressure changes of said fluid body..Iaddend..Iadd. 22. Apparatus for testing a formation intersected by a well bore, said apparatus comprising:     means for maintaining pressure in a body of fluid in a well bore, disposed adjacent a conduit means, at one level while maintaining said body of fluid isolated from a submerged formation to be tested and the interior of said conduit means;   means operable in response to said one level of pressure in said body of fluid, to maintain a flow path leading from said formation through said conduit means in said well bore in a closed condition;   means for changing the pressure of said fluid body while isolating said change in pressure of said fluid body from said formation;   means operable in response to said change in pressure, to permit fluid flow from said formation through said conduit means;   means for further changing the pressure of fluid in said fluid body while isolating said further change in pressure from said formation and the interior of said conduit means;   means, including a closeable sample chamber within said conduit means, operable in response to said further change of pressure of said fluid body, to close and entrap within said closeable sample chamber a sample of fluid from said formation; and   means for securing said sample chamber in said sample entrapping closed condition and for preventing any subsequent opening thereof in response to subsequent pressure changes of said fluid body..Iaddend..Iadd. 23. In a method of offshore testing a submerged formation intersected by a submerged well bore, which method includes:   providing a formation fluid sample entrapping test string extending downwardly from floating vessel means; and   1owering said formation fluid sample entrapping test string from said floating vessel means through conduit means extending upwardly from a submerged well head installation to said floating vessel means; the improvement in said method comprising:     providing a first annular fluid body within said formation fluid sample entrapping test string spaced from and disposed beneath said floating vessel means;   retrievably supporting said formation fluid sample entrapping test string within a submerged well bore intersecting a submerged formation to be tested, with said first annular fluid body being located in said submerged well bore beneath a submerged well head installation and above a packer means, and with said packer means and said submerged well head installation isolating a well annulus portion of said submerged well bore beneath said submerged well head installation and above said packer means from the pressure of said submerged formation to be tested, which annulus portion encircles the outer periphery of said formation fluid sample entrapping test string;     said annulus portion being wholly external of said formation fluid sample entrapping test string,   being located immediately adjacent a casing wall of said submerged well bore, and   defining a second annular body of fluid isolated from said submerged formation and from said conduit means extending upwardly from said submerged well head installation;     providing pressure opposing cooperation between said second annular body of fluid and said first annular body of fluid;   providing within said formation fluid sample entrapping test string a closeable sample chamber having concurrently closeable and openable upper and lower ends, and   opening and closing means responsive to changes in pressure of said second annular body of fluid for alternately, concurrently opening and closing said upper and lower ends,     providing a flow path in said formation fluid sample entrapping test string operable to transmit formation fluid from said submerged formation to said closeable sample chamber within said formation fluid sample entrapping test string, with said flow path extending axially of and through said first annular body of fluid and comprising the interior of said formation fluid sample entrapping test string;     continuously isolating said first annular body of fluid and said second annular body of fluid from fluid pressure of said submerged formation and fluid pressure of said interior of said formation fluid sample entrapping test string;   opposing the pressure of fluid in said first annular fluid body with the pressure of fluid in said second annular fluid body and transmitting the resultant force of said opposing pressures to said closeable fluid sample chamber opening and closing means;   in response to the opposing influences of a lower pressure in said second annular body of fluid in said submerged well bore and pressure of said first annular fluid body, and while said first and second annular fluid bodies are continuously isolated from the fluid pressure of said submerged formation to be tested and said interior of said formation fluid sample entrapping test string, causing said opening and closing means to close said upper and lower ends of said closeable sample chamber;     from said floating vessel means, raising the pressure of said second annular fluid body while continuously isolating said raise in pressure of said second annular fluid body from said submerged formation and said interior of said formation fluid sample entrapping test string;   in response to said raising of pressure in said second annular fluid body, and independent of pressure in said submerged formation and said interior of said formation fluid sample entrapping test string and, while isolating pressures in said submerged formation and said interior of said formation fluid sample entrapping test string from each of said first and second annular fluid bodies, causing said opening and closing means to permit fluid to flow from said submerged formation through said flow path and axially through said first annular fluid body and through said closeable sample chamber;     from said floating vessel means, reducing the pressure of fluid in said second annular fluid body, while isolating said reduction in pressure therein from said submerged formation and from said interior of said formation fluid sample entrapping test string;   in response to said reducing of pressure in said second annular fluid body, and independent of pressures in said submerged formation and said interior of said formation fluid sample entrapping test string, and while isolating pressures in said submerged formation and said interior of said formation fluid entrapping test string from each of said first and second annular fluid bodies, causing said opening and closing means to close said upper and lower ends of said closeable sample chamber and entrap a sample of fluid from said submerged formation therewithin;     from said floating vessel means, effecting a subsequent increase in pressure in said second annular fluid body; and   in response to said subsequent increase in pressure said second annular fluid body, securing said opening and closing means in a condition closing said upper and lower ends of said closeable sample chamber, and   preventing further opening of said upper and lower ends of said closeable sample chamber while said closeable sample chamber remains in said submerged well bore, regardless of further pressure changes in said second     
     
     
        annular fluid body..Iaddend..Iadd. 24.  In a method of offshore testing a submerged formation intersected by a submerged well bore, which method includes: providing a formation fluid sample entrapping test string extending downwardly from floating vessel means; and   1owering said formation fluid sample entrapping test string from said floating vessel means through conduit means extending upwardly from a submerged well head installation to said floating vessel means; the improvement in said method comprising:     providing a first fluid body within said formation fluid sample entrapping test string spaced from and disposed beneath said floating vessel means;   retrievably supporting said formation fluid sample entrapping test string within a submerged well bore intersecting a submerged formation to be tested, with said first fluid body being located in said submerged well bore beneath a submerged well head installation and above a packer means, and     with said packer means and said submerged well head installation being disposed, respectively, below and above a well annulus portion of said submerged well bore, which annulus portion encircles the outer periphery of said formation fluid sample entrapping test string;   said annulus portion being external of said formation fluid sample entrapping test string,   being located immediately adjacent a casing wall of said submerged well bore, and   defining a second annular body of fluid isolated from said submerged formation;     providing pressure opposing cooperation between said second annular body of fluid and said first body of fluid;   providing within said formation fluid sample entrapping test string a closeable sample chamber having closeable and openable upper and lower ends, and   opening and closing means responsive to changes in pressure of said second annular body of fluid for alternately, opening and closing said upper and lower ends,     providing a flow path in the interior of said formation fluid sample entrapping test string operable to transmit formation fluid from said submerged formation to said closeable sample chamber within said formation fluid sample entrapping test string;   continuously isolating said first body of fluid and said second annular body of fluid from fluid pressure of said submerged formation and fluid pressure of said flow path of said formation fluid sample entrapping test string;   opposing the pressure of fluid in said first fluid body with the pressure of fluid in said second annular fluid body and transmitting the resultant force of said opposing pressures to said closeable fluid sample chamber opening and closing means;   in response to the opposing influences of a lower pressure in said second annular body of fluid in said submerged well bore and pressure of said first fluid body, and while said first fluid body and second annular fluid body are continuously isolated from the fluid pressure of said submerged formation to be tested and said flow path of sad formation fluid sample entrapping test string, causing said opening and closing means to close said upper and lower ends of said closeable sample chamber;     from said floating vessel means, raising the pressure of said second annular fluid body while continuously isolating said raise in pressure of said second annular fluid body from said submerged formation and said flow path of said formation fluid sample entrapping test string;   in response to said raising of pressure in said second annular fluid body, and independent of pressure in said submerged formation and said flow path of said formation fluid sample entrapping test string and while isolating pressures in said submerged formation and said flow path of said formation fluid sample entrapping test string from each of said first fluid body and second annular fluid bodies, causing said opening and closing means to permit fluid to flow from said submerged formation through said flow path and through said closeable sample chamber;     from said floating vessel means, reducing the pressure of fluid in said second annular fluid body, while isolating said reduction in pressure therein from said submerged formation and from said flow path of said formation fluid sample entrapping test string;   in response to said reducing of pressure in said second annular fluid body, and independent of pressures in said submerged formation and said flow path of said formation fluid sample entrapping test string, and while isolating pressures in said submerged formation and said flow path of said formation fluid entrapping test string from each of said first fluid body and second annular fluid body, causing said opening and closing means to close said upper and lower ends of said closeable sample chamber and entrap a sample of fluid from said submerged formation therewithin;     from said floating vessel means, effecting a subsequent increase in pressure in said second annular fluid body; and   in response to said subsequent increase in pressure in said second annular fluid body, securing said opening and closing means in a condition closing said upper and lower ends of said closeable sample chamber, and   preventing further opening of said upper and lower ends of said closeable sample chamber while said closeable sample chamber remains in said submerged well bore, regardless of further pressure changes in said second     
     
     
        annular fluid body..Iaddend. .Iadd. 25.  A method of offshore testing a submerged formation intersected by a submerged well bore, which method includes: providing a formation fluid sample entrapping test string extending downwardly from floating vessel means; and   1owering said formation fluid sample entrapping test string from said floating vessel means through conduit means extending upwardly from a submerged well head installation to said floating vessel means; the improvement in said method comprising:     providing a first fluid body within said formation fluid sample entrapping test string spaced from and disposed beneath said floating vessel means;   retrievably supporting said formation fluid sample entrapping test string within a submerged well bore intersecting a submerged formation to be tested, with said first fluid body being located in said submerged well bore beneath a submerged well head installation and above a packer means, and     with said packer means and said submerged well head installation being disposed, respectively, below and above a well annulus portion of said submerged well bore, which annulus portion encircles the outer periphery of said formation fluid sample entrapping test string;   said annulus portion being external of said formation fluid sample entrapping test string,   being located immediately adjacent a casing wall of said submerged well bore, and   defining a second annular body of fluid isolated from said submerged formation;     providing pressure opposing cooperation between said second annular body of fluid and said first body of fluid;   providing within said formation fluid sample entrapping test string a closeable sample chamber having closeable and openable upper and lower ends, and   opening and closing means responsive to changes in pressure of said second annular body of fluid for alternately, opening and closing said upper and lower ends,     providing a flow path in tne interior of said formation fluid sample entrapping test string operable to transmit formation fluid from said submerged formation to said closeable sample chamber within said formation fluid sample entrapping test string;   continuously isolating said first body of fluid and said second annular body of fluid from fluid pressure of said submerged formation and fluid pressure of said flow path of said formation fluid sample entrapping test string;   opposing the pressure of fluid in said first fluid body with the pressure of fluid in said second annular fluid body and transmitting the resultant force of said opposing pressures to said closeable fluid sample chamber opening and closing means;   in response to the opposing influences of pressure in said second annular body of fluid in said submerged well bore and pressure of said first fluid body, and while said first fluid body and second annular fluid body are continuously isolated from the fluid pressure of said submerged formation to be tested and said flow path of said formation fluid sample entrapping test string, causing said opening and closing means to close said upper and lower ends of said closeable sample chamber;     from said floating vessel means, raising the pressure of said second annular fluid body while continuously isolating said raise in pressure of said second annular fluid body from said submerged formation and said flow path of said formation fluid sample entrapping test string;   in response to said raising of pressure in said second annular fluid body, and independent of pressure in said submerged formation and said flow path of said formation fluid sample entrapping test string and, while isolating pressures in said submerged formation and said flow path of said formation fluid sample entrapping test string from each of said first fluid body and second annular fluid body, causing said opening and closing means to permit fluid to flow from said submerged formation through said flow path and through said closeable sample chamber;     from said floating vessel means, changing the pressure of fluid in said second annular fluid body, while isolating said change in pressure therein from said submerged formation and from said flow path of said formation fluid sample entrapping test string;   in response to said changing of pressure in said second annular fluid body, and independent of pressures in said submerged formation and said flow path of said formation fluid sample entrapping test string, and while isolating pressures in said submerged formation and said flow path of said formation fluid entrapping test string from each of said first fluid body and second annular fluid body, causing said opening and closing means to close said upper and lower ends of said closeable sample chamber and entrap a sample of fluid from said     
     
     
        submerged formation therewith..Iaddend..Iadd. 26.  In an apparatus for offshore testing a submerged formation intersected by a submerged well bore, said apparatus includes: floating vessel means;   a submerged well head installation;   a casing wall extending downwardly from said submerged well head installation into a submerged well bore; with said submerged well bore intersecting a submerged formation to be tested;     conduit means extending upwardly from said submerged well head installation to said floating vessel means; and   a formation fluid sample entrapping test string extending downwardly from said floating vessel means through said conduit means and into said submerged well bore, said sample entrapping test string including and supporting releasable packer means,   extending through said submerged well head installation, and   being sealingly and releasably connected to said casing wall by said packer means; the improvement in said apparatus comprising:       a first annular fluid body disposed within said formation fluid sample entrapping test string spaced from and disposed beneath said floating vessel means;   means retrievably supporting said formation fluid sample entrapping test string within said submerged well bore, with said first annular fluid body being located in said submerged well bore beneath said submerged well head installation and above said packer means, and   with said packer means and said submerged well head installation isolating a well annulus portion of said submerged well bore beneath said submerged well head installation and above said packer means from the pressure of said submerged formation to be tested, which annulus portion encircles the outer periphery of said formation fluid sample entrapping test string;     said annulus portion being wholly external of said formation fluid sample entrapping test string,   being located immediately adjacent a casing wall of said submerged well bore, and   defining a second annular body of fluid isolated from said submerged formation and from said conduit means extending upwardly from said submerged well head installation;     means providing pressure opposing cooperation between said second annular body of fluid and said first annular body of fluid;   means providing, within said formation fluid sample entrapping test string, a closeable sample chamber having concurrently closeable and openable upper and lower ends, and   opening and closing means responsive to changes in pressure of said second annular body of fluid for alternately, concurrently opening and closing said upper and lower ends,     means providing a flow path in said formation fluid sample entrapping test string operable to transmit formation fluid from said submerged formation to said closeable sample chamber within said formation fluid sample entrapping test string, with said flow path extending axially of and through said first annular body of fluid and comprising the interior of said formation fluid sample entrapping test string;     means for continuously isolating said first annular body of fluid and said second annular body of fluid from fluid pressure of said submerged formation and fluid pressure of said interior of said formation fluid sample entrapping test string;   means for opposing the pressure of fluid in said first annular fluid body with the pressure of fluid in said second annular fluid body and transmitting the resultant force of said opposing pressures to said closeable fluid sample chamber opening and closing means;   means operable in response to the opposing influences of a lower pressure in said second annular body of fluid in said submerged well bore and pressure of said first annular fluid body, and while said first and second annular fluid bodies are continuously isolated from the fluid pressure of said submerged formation to be tested and said interior of said formation fluid sample entrapping test string, to cause said opening and closing means to close said upper and lower ends of said closeable sample chamber;     means operable from said floating vessel means to raise the pressure of said second annular fluid body while continuously isolating said raise in pressure of said second annular fluid body from said submerged formation and said interior of said formation fluid sample entrapping test string;   means operable, in response to said raising of pressure in said second annular fluid body, and independent of pressure in said submerged formation and said interior of said formation fluid sample entrapping test string and, while isolating pressures in said submerged formation and said interior of said formation fluid sample entrapping test string from each of said first and second annular fluid bodies, to cause said opening and closing means to permit fluid to flow from said submerged formation through said flow path and axially through said first annular fluid body and through said closeable sample chamber;     means operable from said floating vessel means to reduce the pressure of fluid in said second annular fluid body, while isolating said reduction in pressure therein from said submerged formation and from said interior of said formation fluid sample entrapping test string;   means operable in response to said reducing of pressure in said second annular fluid body, and independent of pressures in said submerged formation and said interior of said formation fluid sample entrapping test string, and while isolating pressures in said submerged formation and said interior of said formation fluid entrapping test string from each of said first and second annular fluid bodies, to cause said opening and closing means to close said upper and lower ends of said closeable sample chamber and entrap a sample of fluid from said submerged formation therewithin;     means operable from said floating vessel means to effect a subsequent increase in pressure in said second annular fluid body; and   means operable in response to said subsequent increase in pressure in said second annular fluid body, to secure said opening and closing means in a condition closing said upper and lower ends of said closeable sample chamber, and   prevent further opening of said upper and lower ends of said closeable sample chamber while said closeable sample chamber remains in said submerged well bore, regardless of further pressure changes in said second     
     
     
        annular fluid body. .Iaddend..Iadd. 27.  In an apparatus for offshore testing a submerged formation intersected by a submerged well bore, which apparatus includes: a floating vessel means;   a submerged well head installation;   a casing wall exending downwardly from said submerged well head installation into a submerged well bore; with said submerged well bore intersecting a submerged formation to be tested;     conduit means extending upwardly from said submerged well head installation to said floating vessel means; and   a formation fluid sample entrapping test string extending downwardly from said floating vessel means through said conduit means and into said submerged well bore, said sample entrapping test string including and supporting releasable packer means,   extending through said submerged well head installation, and   being sealingly and releasably connected to said casing wall by said packer means; the improvement in said apparatus comprising:       a first fluid body disposed within said formation fluid sample entrapping test string spaced from and disposed beneath said floating vessel means;   means retrievably supporting said formation fluid sample entrapping test string within said submerged well bore, with said first fluid body being located in said submerged well bore beneath aid submerged well head installation and above said packer means, and   with said packer means and said submerged well head installation being disposed, respectively, below and above a well annulus portion of said submerged well bore, which annulus portion encircles the outer periphery of said formation fluid sample entrapping test string;     said annulus portion being external of said formation fluid sample entrapping test string,   being located immediately adjacent a casing wall of said submerged well bore, and   defining a second annular body of fluid isolated from said submerged formation;     means providing pressure opposing cooperation between said second annular body of fluid and said first body of fluid;   means providing, within said formation fluid sample entrapping test string, a closeable sample chamber having closeable and openable upper and lower ends, and   opening and closing means responsive to changes in pressure of said second annular body of fluid for alternately, opening and closing said upper and lower ends,     means providing a flow path in the interior of said formation fluid sample entrapping test string operable to transmit formation fluid from said submerged formation to said closeable sample chamber within said formation fluid sample entrapping test string;   means for continuously isolating said first body of fluid and said second annular body of fluid from fluid pressure of said submerged formation and fluid pressure of said flow path of said formation fluid sample entrapping test string;   means for opposing the pressure of fluid in said first fluid body with the pressure of fluid in said second annular fluid body and transmitting the resultat force of said opposing pressures to said closeable fluid sample chamber opening and closing means;   means operable in response to the opposing influences of a lower pressure in said second annular body of fluid in said submerged well bore and pressure of said first fluid body, and while said first fluid body and second annular fluid body are continuously isolated from the fluid pressure of said submerged formation to be tested and said flow path of said formation fluid sample entrapping test string, to cause said opening and closing means to close said upper and lower ends of said closeable sample chamber;     means operable from said floating vessel means to raise the pressure of said second annular fluid body while continuously isolating said raise in pressure of said second annular fluid body from said submerged formation and said flow path of said formation fluid sample entrapping test string;   means operable, in response to said raising of pressure in said second annular fluid body, and independent of pressure in said submerged formation and said flow path of said formation fluid sample entrapping test string and, while isolating pressures in said submerged formation and said flow path of said formation fluid sample entrapping test string from each of said first fluid body and second annular fluid body, to cause said opening and closing means to permit fluid to flow from said submerged formation through said flow path and through said closeable sample chamber;     means operable from said floating vessel means to reduce the pressure of fluid in said second annular fluid body, while isolating said reduction in pressure therein from said submerged formation and from said flow path of said formation fluid sample entrapping test string;   means operable in response to said reducing of pressure in said second annular fluid body, and independent of pressures in said submerged formation and said flow path of said formation fluid sample entrapping test string, and while isolating pressures in said submerged formation and said flow path of said formation fluid entrapping test string from each of said first fluid body and second annular fluid body, to cause said opening and closing means to close said upper and lower ends of said closeable sample chamber and entrap a sample of fluid from said submerged formation therewithin;     means operable from said floating vessel means to effect a subsequent increase in pressure in said second annular fluid body; and   means operable in response to said subsequent increase in pressure in said second annular fluid body, to secure said opening and closing means in a condition closing said upper and lower ends of said closeable sample chamber, and   prevent further opening of said upper and lower ends of said closeable sample chamber while said closeable sample chamber remains in said submerged well bore, regardless of further pressure changes in said second     
     
     
        annular fluid body..Iaddend..Iadd. 28.  In an apparatus for offshore testing a submerged formation intersected by a submerged well bore, which apparatus includes: floating vessel means;   a submerged well head installation;   a casing wall extending downwardly from said submerged well head installation into a submerged well bore; with said submerged well bore intersecting a submerged formation to be tested     conduit means extending upwardly from said submerged well head installation to said floating vessel means; and   a formation fluid sample entrapping test string extending downwardly from said floating vessel means through said conduit means and into said submerged well bore, and said sample entrapping test string including and supporting releasable packer means   extending through said submerged well head installation, and   being sealingly and releasably connected to said casing wall by said packer means; the improvement in said apparatus comprising:       a first fluid body disposed within said formation fluid sample entrapping test string spaced from and disposed beneath said floating vessel means;   means retrievable supporting said formation fluid sample entrapping test string within said submerged well bore, with said first fluid body being located in said submerged well bore beneath said submerged well head installation and above said packer means, and   with said packer means and said submerged well head installation being disposed, respectively, below and above a well annulus portion of said submerged well bore, which annulus portion encircles the outer periphery of formation fluid sample entrapping test string;     said annulus portion being external of said formation fluid sample entrapping test string,   being located immediately adjacent a casing wall of said submerged well bore, and   defining a second annular body of fluid isolated from said submerged formation;     means providing pressure opposing cooperation between said second annular body of fluid and said first body of fluid;   means providing, within said formation fluid sample entrapping test string, a closeable sample chamber having closeable and openable upper and lower ends, and   opening and closing means responsive to changes in pressure of said second annular body of fluid for alternately opening and closing said upper and lower ends,     means providing a flow path in the interior of said formation fluid sample entrapping test string operable to transmit formation fluid from said submerged formation to said closeable sample chamber within said formation fluid sample entrapping test string;   means for continuously isolating said first body of fluid and said second annular body of fluid from fluid pressure of said submerged formation and fluid pressure of said flow path of said formation fluid sample entrapping test string;   means for opposing the pressure of fluid in said first fluid body with the pressure of fluid in said second annular fluid body and transmitting the resultant force of said opposing pressures to said closeable fluid sample chamber opening and closing means;   means operable in response to the opposing influences of pressure in said second annular body of fluid in said submerged well bore and pressure of said first fluid body, and while said first fluid body and second annular fluid body are continuously isolated from the fluid pressure of said submerged formation to be tested and said flow path of said formation fluid sample entrapping test string, to cause said opening and closing means to close said upper and lower ends of said closeable sample chamber;     means operable from said floating vessel means to raise the pressure of said second annular fluid body while continuously isolating said raise in pressure of said second annular fluid body from said submerged formation and said flow path of said formation fluid sample entrapping test string;   means operable, in response to said raising of pressure in said second annular fluid body, and independent of pressure in said submerged formation and said flow path of said formation fluid sample entrapping test string and while isolating pressures in said submerged formation and said flow path of said formation fluid sample entrapping test string from each of said first fluid body and second annular fluid body, to cause said opening and closing means to permit fluid to flow from said submerged formation through said flow path and through said closeable sample chamber;     means operable from said floating vessel means to change the pressure of fluid in said second annular fluid body, while isolating said change in pressure therein from said submerged formation and from said flow path of said formation fluid sample entrapping test string;   means operable in response to said changing of pressure in said second annular fluid body, and independent of pressures in said submerged formation and said flow path of said formation fluid sample entrapping test string, and while isolating pressures in said submerged formation and said flow path of said formation fluid entrapping test string from each of said first fluid body and second annular fluid body, to cause said opening and closing means to close said upper and lower ends of said closeable sample chamber and entrap a sample of fluid from said     
     
     
        submerged formation therewithin. .Iaddend.  .Iadd.29.  A method of testing a submerged formation intersected by a well bore having a lower portion extending from the sea floor to the formation to be tested and an upper well bore portion extending from the sea floor to a work station at the surface of the sea, said method comprising: maintaining pressure in a body of fluid in said well bore, disposed in an annulus of said well bore external of a conduit means and adjacent a casing lining the lower portion of said well bore, at one level while maintaining said body of fluid isolated from said submerged formation to be tested, the interior of said conduit means and said upper well bore portion;   in response to said one level of pressure in said body of fluid, maintaining a flow path leading from said formation through said conduit means in said well bore in a closed condition;   changing the pressure of said fluid body while isolating said change in pressure of said fluid body from said formation, the flow path through said conduit means and said upper well bore portion;   in response to said change in pressure, permitting fluid to flow from said formation through said conduit means;   further changing the pressure of fluid in said fluid body while isolating said further change in pressure from said formation, the flow path through said conduit means and said upper well bore portion;   in response to said further change of pressure of said fluid body and independent of the pressure in the flow path through said conduit means, entrapping between upper and lower valve means within said conduit means located in said well bore adjacent said fluid filled annulus, a sample of   
     
     
        fluid from said formation. .Iaddend..Iadd. 30.  A method of testing a submerged formation from an offshore test site having an upper well bore portion extending from a work station at the surface of the sea to the sea floor and a submerged well bore extending from the sea floor to the formation to be tested, said method comprising: maintaining pressure in a body of fluid in said submerged well bore, disposed in an annulus of said submerged well bore external of a conduit means and adjacent a casing lining said submerged well bore, at a relatively low level while maintaining said body of fluid isolated from said submerged formation to be tested, the interior of said conduit means and said upper well bore portion;   in response to said relatively low level of pressure in said body of fluid, maintaining a flow path leading from said formation through said conduit means in said submerged well bore in a closed condition;   increasing the pressure of said fluid body while isolating said increase in pressure of said fluid body from said formation, the flow path through said conduit means and said upper well bore portion;   in response to said increase in pressure, permitting fluid to flow from said formation through said conduit means;   decreasing the pressure of fluid in said fluid body while isolating said decrease in pressure from said formation, the flow path through said conduit means and said upper well bore portion; and   in response to said decrease of pressure of said fluid body and independent of the pressure in the flow path through said conduit means, entrapping between upper and lower valve means within said conduit means located in said well bore adjacent said fluid filled annulus, a sample of fluid from   
     
     
        said formation. .Iaddend..Iadd. 31.  Apparatus for testing a submerged formation intersected by a well bore having a lower portion extending from the sea floor to the formation to be tested and an upper well bore portion extending from the sea floor to a work station at the surface of the sea, said apparatus comprising: conduit means in said well bore having a flow path therethrough for providing a fluid passageway from said formation through said well bore;   means for maintaining pressure in a body of fluid in said well bore, disposed in an annulus of said well bore external of said conduit means and adjacent a casing lining the lower portion of said well bore, at one level while maintaining said body of fluid isolated from said submerged formation to be tested, the flow path through said conduit means and said upper well bore portion;   means operable in response to said one level of pressure in said body of fluid, to maintain said flow path leading from said formation through said conduit means in said well bore in a closed condition;   means for changing the pressure of said fluid body while isolating said change in pressure of said fluid body from said formation, the flow path through said conduit means and said upper well bore portion;   means operable in response to said change in pressure, to permit fluid to flow from said formation through said conduit means;   means for further changing the pressure of fluid in said fluid body while isolating said further change in pressure from said formation, the flow path through said conduit means and said upper well bore portion; and   means, including upper and lower valve means located in said conduit means adjacent said fluid filled annulus, operable in response to said further change of pressure of said fluid body independent of the pressure in the flow path through said conduit means, to entrap between said upper and lower valve means within said conduit means a sample of fluid from said   
     
     
        formation. .Iaddend..Iadd. 32.  Apparatus for testing a submerged formation from an offshore test site having an upper well bore portion extending from a work station at the surface of the sea to the sea floor and a submerged well bore extending from the sea floor to the formation to be tested, said apparatus comprising: conduit means in said well bores having a flow path therethrough for providing a fluid passageway from said formation through said well bores;   means for maintaining pressure in a body of fluid in said submerged well bore, disposed in an annulus of said submerged well bore external of said conduit means and adjacent a casing lining said submerged well bore, at a relatively low level while maintaining said body of fluid isolated from said formation to be tested, the flow path through said conduit means and said upper well bore portion;   means operable in response to said relatively low level of pressure in said body of fluid, to maintain said flow path leading from said formation through said conduit means in said submerged well bore in a closed condition;   means for increasing the pressure of said fluid body while isolating said increase in pressure of said fluid body from said formation, the flow path through said conduit means and said upper well bore portion;   means operable in response to said increase in pressure to permit fluid to flow from said formation through said conduit means;   means for decrasing the pressure of fluid in said fluid body while isolating said decrease in pressure from said formation, the flow path through said conduit means and said upper well bore portion;   means, including upper and lower valve means located in said conduit means adjacent said fluid filled annulus, operable in response to said decrease of pressure of said fluid body independent of the pressure in the flow path through said conduit means, to entrap between said upper and lower valve means within said conduit means a sample of fluid from said formation..Iaddend.