Method to solids-pack non-vertical wellbores

Abstract

A method of preparing a solids-pack for use in oilfield completion operations involves staged pumping using two distinct types of carrier fluid with distinct solids loadings during the solids deposition process. The method can be employed in packing of non-vertical oilfield wellbores for formation stabilization, fracture stabilization and/or sand control, particularly around sand exclusion devices. In preferred embodiments the method results in greater uniformity of packing, and also offers the advantage of much more rapid deposition and therefore of completion of the pack phase, reducing overall rig time.

What is claimed is:  
     
         1 . A method of solids-packing non-vertical wellbores comprising pumping into the wellbore a high apparent viscosity carrier fluid containing a relatively higher amount of solids during at least the earlier portion of alpha wave deposition, then pumping into the wellbore a low apparent viscosity carrier fluid containing a relatively lower amount of solids during the later portion, if any, of the alpha wave deposition and during beta wave deposition, such that a solids-pack is formed.  
     
     
         2 . The method of  claim 1  wherein the high apparent viscosity carrier fluid has an apparent viscosity of from about 5 to about 20 centipoise at 511 second −1 , as represented under downhole conditions.  
     
     
         3 . The method of  claim 2  wherein the high apparent viscosity carrier fluid has an apparent viscosity from about 8 to about 15 centipoise at 511 second −1 , as represented under downhole conditions.  
     
     
         4 . The method of  claim 1  wherein the low apparent viscosity carrier fluid has an apparent viscosity of from about 0.25 to less than about 5 centipoise at 511 second −1 , as represented under downhole conditions.  
     
     
         5 . The method of  claim 1  wherein the relatively higher amount of solids is from about 3 to about 6 pounds per gallon added.  
     
     
         6 . The method of  claim 5  wherein the relatively higher amount of solids is from about 3 to about 4 pounds per gallon added.  
     
     
         7 . The method of  claim 1  wherein the relatively lower amount of solids is from about 0.1 to about 2.5 pounds per gallon added.  
     
     
         8 . The method of  claim 1  wherein the high apparent viscosity carrier fluid comprises a brine, a viscoelastic surfactant, or both.  
     
     
         9 . The method of  claim 8  wherein the high apparent viscosity carrier fluid comprises both a viscoelastic surfactant and a brine, and the viscoelastic surfactant is present in an amount from about 1 to about 6 percent by volume based on total volume.  
     
     
         10 . The method of  claim 1  wherein the low apparent viscosity carrier fluid comprises a brine, a viscosity reducer, or both.  
     
     
         11 . The method of  claim 10  wherein the low apparent viscosity carrier fluid comprises both a brine and a viscosity reducer, and the viscosity reducer is present in an amount from about 1 to about 20 percent by volume based on total volume.  
     
     
         12 . The method of  claim 11  wherein the viscosity reducer is present in an amount from about 1 to about 10 percent by volume based on total volume.  
     
     
         13 . The method of  claim 1  wherein the high apparent viscosity carrier fluid is used during about the earlier 70 to 100 percent of the alpha wave deposition, and the low apparent viscosity carrier fluid is used during about the later 0 to 30 percent of the alpha wave deposition and during beta wave deposition.  
     
     
         14 . The method of  claim 13  wherein high apparent viscosity carrier fluid is used during about the earlier 90 to 100 percent of the alpha wave deposition, and the low apparent viscosity carrier fluid is used during about the later 0 to 10 percent of the alpha wave deposition and during beta wave deposition.  
     
     
         15 . The method of  claim 1  wherein the solids pack is a gravel-pack surrounding a sand exclusion device or a proppant pack in a reservoir fracture zone.  
     
     
         16 . A method of solids-packing of non-vertical wellbores comprising pumping into the wellbore a high apparent viscosity carrier fluid, having an apparent viscosity of from about 5 to about 20 centipoise at 511 second −1 , the high apparent viscosity carrier fluid containing a relatively higher amount of solids, during at least the earlier portion of alpha wave deposition; then pumping into the wellbore a low apparent viscosity carrier fluid, having an apparent viscosity of from about 0.25 to less than about 5 centipoise at 511 second −1 , the low apparent viscosity carrier fluid containing a relatively lower amount of solids, during the later portion, if any, of the alpha wave deposition and during beta wave deposition; both apparent viscosities as represented under downhole conditions; such that a solids-pack is formed.  
     
     
         17 . The method of  claim 16  wherein the high apparent viscosity carrier fluid contains from about 3 to about 6 pounds per gallon added of solids, and the low apparent viscosity carrier fluid contains from about 0.1 to about 2.5 pounds per gallon added of solids.  
     
     
         18 . The method of  claim 17  wherein the high apparent viscosity carrier fluid includes a brine, a viscoelastic surfactant, or both, and the low apparent viscosity carrier fluid includes a brine, a viscosity reducer, or both.  
     
     
         19 . A method of solids-packing of non-vertical wellbores comprising pumping into the wellbore a high apparent viscosity carrier fluid, having an apparent viscosity of from about 5 to about 20 centipoise at 511 second 1 , the high apparent viscosity carrier fluid containing from about 3 to about 6 pounds per gallon added of solids, during at least the earlier portion of alpha wave deposition; then pumping into the wellbore a low apparent viscosity carrier fluid, having an apparent viscosity of from about 0.25 to less than about 5 centipoise at 511 second −1 , the low apparent viscosity carrier fluid containing from about 0.1 to about 2.5 pounds per gallon added of solids, during the later portion, if any, of the alpha wave deposition and during beta wave deposition; both apparent viscosities as represented under downhole conditions; such that a solids-pack is formed.  
     
     
         20 . The method of  claim 19  wherein the high apparent viscosity carrier fluid comprises a brine, a viscoelastic surfactant, or both, and the low apparent viscosity carrier fluid comprises a brine, a viscosity reducer, or both.