Enhanced Shale Oil Production By In Situ Heating Using Hydraulically Fractured Producing Wells

Abstract

A method for enhanced production of hydrocarbon fluids from an organic-rich rock formation such as an oil shale formation is provided. The method generally includes completing at least one heater well in the organic-rich rock formation, and also completing a production well in the organic-rich rock formation. The method also includes the steps of hydraulically fracturing the organic-rich rock formation from the production well such that one or more artificial fractures are formed, and heating the organic-rich rock formation from the at least one heater well, thereby pyrolyzing at least a portion of the organic-rich rock into hydrocarbon fluids Pyrolyzing the organic-rich rock formation creates thermal fractures in the formation due to thermal stresses created by heating. The thermal fractures intersect the artificial fractures. As an additional step, hydrocarbon fluids may be produced from the production well. Preferably, the organic-rich rock formation is an oil shale formation.

1 . A method for producing hydrocarbon fluids from an organic-rich rock formation, comprising:
 completing at least one heater well in the organic-rich rock formation;   completing a production well in the organic-rich rock formation;   hydraulically fracturing the organic-rich rock formation from the production well such that one or more artificial fractures are formed;   heating the organic-rich rock formation from the at least one heater well, thereby pyrolyzing at least a portion of the organic-rich rock into hydrocarbon fluids and thereby creating thermal fractures in the organic-rich rock formation due to thermal stresses created by heating, the thermal fractures intersecting the artificial fractures; and   producing hydrocarbon fluids from the production well.   
     
     
         2 . The method of  claim 1 , wherein the organic-rich rock formation is an oil shale formation. 
     
     
         3 . The method of  claim 2 , wherein the thermal fractures are substantially horizontal. 
     
     
         4 . The method of  claim 2 , wherein the thermal fractures are substantially vertical. 
     
     
         5 . The method of  claim 2 , further comprising:
 performing geomechanical modeling to determine the direction and extent of thermal fractures.   
     
     
         6 . The method of  claim 2  wherein the thermal fractures are at least partially formed in a first portion of the oil shale formation which has not been heated to the extent of a second portion of the oil shale formation which is more proximate the at least one heater well. 
     
     
         7 . The method of  claim 2 , wherein the step of hydraulically fracturing the oil shale formation is performed before the step of heating the oil shale formation. 
     
     
         8 . The method of  claim 2 , wherein the step of hydraulically fracturing the oil shale formation is performed after the step of heating the oil shale formation has begun, but before the substantial formation of thermal fractures. 
     
     
         9 . The method of  claim 2 , further comprising:
 determining a distance from the production well in which to form the one or more artificial fractures in order to provide fluid communication with anticipated thermal fractures.   
     
     
         10 . The method of  claim 2 , wherein the artificial fractures propagate a distance no more than half of the distance toward a heater well. 
     
     
         11 . The method of  claim 2 , wherein the thermal fractures intersect at least one of the artificial fractures formed from hydraulically fracturing within one year of initiating heating. 
     
     
         12 . The method of  claim 2  wherein the step of heating results in at least a portion of the oil shale formation reaching a temperature of 270° C. or greater. 
     
     
         13 . The method of  claim 2 , wherein the artificial fractures from the production well are vertical in orientation. 
     
     
         14 . The method of  claim 2 , wherein the artificial fractures from the production well are horizontal in orientation. 
     
     
         15 . The method of  claim 2 , wherein the artificial fractures are formed in the direction perpendicular to that of least horizontal principal stress in the oil shale formation. 
     
     
         16 . The method of  claim 2 , further comprising introducing a proppant material into one or more of the artificial fractures. 
     
     
         17 . A method for producing hydrocarbons from an oil shale formation, comprising:
 completing a production well substantially vertically;   hydraulically fracturing the oil shale formation from the production well in a vertical orientation, such that artificial fractures are formed;   completing at least two heater wells that are substantially horizontal within the oil shale formation;   heating the oil shale formation in situ from the at least two heater wells, thereby creating horizontal fractures due to thermal stresses within the oil shale formation which intersect the artificial fractures, and also thereby converting at least a portion of the oil shale formation into hydrocarbon fluids by pyrolysis; and   producing hydrocarbon fluids from the production well.   
     
     
         18 . The method of  claim 17 , wherein the hydraulic fractures are formed in the direction perpendicular to that of least horizontal principal stress in the oil shale formation. 
     
     
         19 . The method of  claim 17 , further comprising introducing a proppant material into one or more of the hydraulic fractures. 
     
     
         20 . A well pattern for a hydrocarbon fluids production program, comprising:
 a plurality of heater wells completed in an organic-rich rock formation comprising oil shale;   a plurality of production wells completed in the organic-rich rock formation, the heater wells and production wells forming a repeating well pattern, the well pattern having been determined by:   estimating the extent of a hydraulic fracture from each of the production wells,   estimating the extent of a thermal fracture resulting from heating of the subsurface formation from corresponding heater wells, and   locating the plurality of production wells and corresponding heater wells such that the hydraulic fractures and thermal fractures from the plurality of production wells and the corresponding heater wells are estimated to intersect, thereby forming intersection zones within the well pattern.   
     
     
         21 . The method of  claim 20 , wherein the production wells are hypothetical wells that have not actually been completed in the subsurface formation. 
     
     
         22 . The method of  claim 20 , wherein the intersection zones are planar zones, volumetric zones, or linear zones. 
     
     
         23 . The method of  claim 20 , wherein the thermal fractures are substantially horizontal. 
     
     
         24 . The method of  claim 20 , wherein:
 the thermal fractures are substantially vertical; and   the hydraulic fractures from the production wells are vertical in orientation.   
     
     
         25 . The method of  claim 20 , wherein the hydraulic fractures are formed in the direction perpendicular to that of least horizontal principal stress in the oil shale formation.