Geomechanical weakening with surface acting agents

Abstract

A method of hydraulic fracturing of a reservoir to improve drainage.

1 ) A method of hydraulic fracturing of a reservoir to improve drainage, said method comprising:
 a) obtaining a core sample from a reservoir;   b) testing said core sample with a plurality of test surfactants mixed in a hydraulic fracturing fluid and measuring one or more of i) fracture propagation pressure, ii) fracture toughness, or iii) fracture bifurcation index;   c) selecting one or more optimal surfactant(s) for propagating fractures based on the results from step b); and   d) fracturing said reservoir with a fracturing fluid containing said optimal surfactant(s).   
     
     
         2 ) The method of  claim 1 , wherein said fracturing is by cyclic fracturing with one or more rest periods. 
     
     
         3 ) The method of  claim 1 , wherein said fracturing is by cyclic fracturing with one or more rest periods and one or more reverse flow periods. 
     
     
         4 ) The method of  claim 1 , wherein core sample is maintained under reservoir pressure, temperature and humidity conditions during obtaining step a) and testing step b). 
     
     
         5 ) The method of  claim 1 , wherein said surfactant is use at or above the critical micelle concentration (CMC). 
     
     
         6 ) The method of  claim 1 , wherein said surfactant is use at the CMC ±5%. 
     
     
         7 ) An improved method of hydraulic fracturing comprising injecting a fracturing fluid into a reservoir under sufficient pressure so as to fracture the reservoir; the improvement comprising adding a surfactant to the fracturing fluid in an amount sufficient to reduce fracture propagation pressure or reduce fracture toughness or increase fracture bifurcation index. 
     
     
         8 ) An improved method of hydraulic fracturing comprising injecting a fracturing fluid into a reservoir under sufficient pressure so as to fracture the reservoir; the improvement comprising adding a surfactant to the fracturing fluid in an amount sufficient to cause geomechanical weakening. 
     
     
         9 ) An improved method of hydraulic fracturing comprising i) injecting a fracturing fluid into a reservoir under sufficient pressure so as to fracture the reservoir, followed by ii) a rest period and iii) an optional reverse flow period and repeating steps i-iii); the improvement comprising adding a surfactant to the fracturing fluid in one or more injecting steps i) in an amount sufficient to cause geomechanical weakening. 
     
     
         10 ) A method of propagating an existing fracture in a reservoir; said method comprising:
 a) providing a reservoir with one or more existing fractures,   b) propagating said one or more existing fractures by injection an fracturing fluid plus surfactant present at about the CMC;   c) followed by a shut in period plus an optional reverse flow period, and   d) repeating steps b and c until said reservoir is sufficiently fractured.   
     
     
         11 ) A method of hydraulic fracturing of a reservoir to improve hydrocarbon drainage, said method comprising:
 a) testing a reservoir with a plurality of test surfactants mixed in a hydraulic fracturing fluid and measuring one or more of i) fracture propagation pressure, ii) fracture toughness, or iii) fracture bifurcation index;   b) selecting an optimal surfactant for propagating fractures based on the results from step b); and   c) fracturing said reservoir with a fracturing fluid containing said optimal surfactant.   
     
     
         12 ) The method of  claim 11 , wherein said surfactant is use at the CMC ±10%. 
     
     
         13 ) The method of  claim 11 , wherein said surfactant is use at the CMC ±5%.