Method for fracturing and analyzing an earthen formation surrounding a well bore

Abstract

A method of micro-fracturing in a well bore to define the stress field and fracture system for the purpose of optimizing subsequent hydraulic fracturing well completion operations. During or subsequent to drilling of the well bore, a down hole imager takes measurements that allow the operator to select appropriate zones of the well bore for optional micro-fracture testing. The micro-fracturing testing is conducted by stopping the flow of drilling mud and expanding one, or preferably two packers incorporated into a micro-fracture module of the drill string. The pressure in the isolated zone between the packers (or below the packer if one packer is used) is pressurized until fracture occurs. The trend in the pressure in the isolated zone of the bore hole is measured during the test to assess information about the fracturing of the bore hole. After micro-fracture testing, or upon completion of the drilling, the same zone of the bore hole is again scanned by the imager and the natural beak-outs or pre- and post-micro-fracture testing images are analyzed to ascertain further information about the formation. Micro-fracture testing is repeated over different zones of the well bore as the drilling proceeds or subsequent to the drilling operation and the information from these tests is used to optimize the major fracturing in the completion phase of the drilling.

1 . A method of obtaining and analyzing data concerning an earthen formation, through which a drill bit coupled to a drill string drills a bore hole, in order to acquire information useful in fracturing said formation during or upon completion of said drilling, comprising the steps of:
 a) inserting said drill string into said bore hole, an annular passage extending through said bore hole being formed between said drill string and said bore hole wall when said drill string is inserted into said bore hole;   b) incorporating one or more packers into said drill string, said one or more packers capable of expanding so as to seal at least a portion of said annular passage extending through said bore hole;   c) rotating said drill bit coupled to said drill string so as to drill a first portion of said bore hole in said earthen formation, said drill string extending further into said formation as said drill bit drills said bore hole;   d) selecting a first zone of said bore hole for micro-fracture testing;   e) expanding said one or more packers incorporated into said drill string so as to isolate said annular passage extending through said first zone of said bore hole;   f) pumping a fluid through said drill string and into said annular passage in said first zone of said bore hole so as to increase the pressurize of said fluid in said first zone until said formation proximate said first zone of said bore hole fractures;   g) measuring the pressure in said first zone of said bore hole over time as said fluid is being pumped into said first zone of said bore hole;   h) analyzing said pressure versus time measurement to acquire a first type of information concerning said formation proximate said first zone.   i) repeating steps (d) through (h) in one or more additional zones of said bore hole so as to acquire additional information of said first type concerning said formation proximate said additional zones of said bore hole;   j) using said first type of information acquired in step (i) to conduct fracturing of said bore hole for completion and production purposes.   
     
     
         2 . The method according to  claim 1 , wherein said first type of information concerning said formation acquired in step (h) comprises the pressure in said bore hole when said fracture of said formation initiates in step (f). 
     
     
         3 . The method according to  claim 1 , further comprising the step of stopping pumping said fluid into said first zone of said bore hole and continuing to measure the pressure in said first zone of said bore hole for an additional period of time after stopping said pumping. 
     
     
         4 . The method according to  claim 3 , wherein said first type of information concerning said formation acquired in step (h) comprises the pressure in said bore hole when said fracture in said formation begins closing. 
     
     
         5 . The method according to  claim 1 , further comprising the steps of:
 k) incorporating an imager into said drill string, said imager capable of sensing data of a first type concerning said formation proximate said bore hole;   l) scanning at least a portion said bore hole drilled by said drill bit using said imager so as to obtain said first type of data concerning said formation proximate said scanned portion of said bore hole.   
     
     
         6 . The method according to  claim 5 , wherein the step of selecting said first zone of said bore hole for micro-fracture testing in step (c) is based at least in part on said data obtained from said scanning in step (l). 
     
     
         7 . The method according to  claim 5 , wherein said first type of data comprises the resistivity of said formation. 
     
     
         8 . The method according to  claim 5 , wherein said first type of data comprises the density of said formation. 
     
     
         9 . The method according to  claim 1 , further comprising the steps of:
 k) incorporating an imager into said drill string, said imager capable of sensing data of a first type concerning said formation proximate said bore hole;   l) scanning said first zone of said bore hole using said imager prior to performing step (f) so as to obtain said first type of data concerning said formation proximate said first zone prior to said fracture of said formation proximate first zone in step (f);   m) repeating said scanning of said first zone of said bore hole using said imager subsequent to performing step (f) so as to obtain said first type of data concerning said formation proximate said first zone after said fracture of said formation proximate said first zone in step (f).   
     
     
         10 . The method according to  claim 9 , further comprising the step of:
 n) comparing said first type of data concerning said formation proximate said first zone before said fracture with said first type of data concerning said formation proximate said first zone after said fracture to acquire a second type of information concerning said formation proximate said first zone.   
     
     
         11 . The method according to  claim 10 , further comprising the step of:
 o) using said second type of information acquired in step (n) to conduct fracturing of said bore hole upon completion of said drilling.   
     
     
         12 . The method according to  claim 10 , wherein said second type of information concerning said formation acquired in step (n) concerns the strike of said formation. 
     
     
         13 . The method according to  claim 10 , wherein said second type of information concerning said formation acquired in step (n) concerns the dip of said formation. 
     
     
         14 . The method according to  claim 10 , wherein said second type of information concerning said formation acquired in step (n) concerns the primary fracture orientation of said formation. 
     
     
         15 . The method according to  claim 10 , wherein said second type of information concerning said formation acquired in step (n) concerns the orientation of the maximum and minimum stress axis of said formation. 
     
     
         16 . The method according to  claim 10 , wherein said second type of information concerning said formation acquired in step (n) concerns the aperture of said fracture in said formation. 
     
     
         17 . The method according to  claim 1 , further comprising the step of ceasing said rotation of said drill bit prior to expanding said one or more packers. 
     
     
         18 . The method according to  claim 1 , wherein step (b) comprises incorporating at least first and second packers into said drill string spaced a predetermined distance apart, said first and second packers capable of expanding so as to seal a portion of said annular passage extending between said first and second packers; and wherein step (e) comprises expanding said first and second packers so as to isolate said annular passage extending between said first and second packers and wherein said first zone of said bore hole is disposed between said first and second packers.