Treatment methods for nahcolitic oil shale formations with fractures

Abstract

A method for treating a hydrocarbon containing layer in a subsurface formation includes forming a plurality of substantially vertical fractures in the formation at selected intervals along a length of at least one production wellbore positioned substantially horizontally in the hydrocarbon containing layer. Heat is provided from a plurality of heaters to the hydrocarbon containing layer such that at least some hydrocarbons in the hydrocarbon containing layer are mobilized. At least some of the plurality of heaters are positioned substantially horizontally in the hydrocarbon containing layer. At least some mobilized hydrocarbons are produced through at least one production wellbore.

What is claimed is: 
     
         1 . A method for treating a hydrocarbon containing layer in a subsurface formation, comprising:
 forming a plurality of substantially vertical fractures in the formation at selected intervals along a length of at least one production wellbore positioned substantially horizontally in the hydrocarbon containing layer;   providing heat from a plurality of heaters to the hydrocarbon containing layer such that at least some hydrocarbons in the hydrocarbon containing layer are mobilized, wherein at least some of the plurality of heaters are positioned substantially horizontally in the hydrocarbon containing layer; and   producing at least some mobilized hydrocarbons through at least one production wellbore.   
     
     
         2 . The method of  claim 1 , further comprising forming the fractures at substantially equidistant intervals along the length of the production wellbore. 
     
     
         3 . The method of  claim 1 , wherein the heaters are positioned in heater wellbores. 
     
     
         4 . The method of  claim 1 , wherein the heaters are positioned substantially parallel with the at least one production wellbore. 
     
     
         5 . The method of  claim 1 , wherein the heaters are positioned substantially perpendicular to the at least one production wellbore. 
     
     
         6 . The method of  claim 1 , wherein the fractures have oblong cross-sections. 
     
     
         7 . The method of  claim 1 , wherein the at least one production wellbore is located closer to a bottom of the hydrocarbon containing layer than a top of the hydrocarbon containing layer. 
     
     
         8 . The method of  claim 1 , further comprising providing a proppant to keep one or more of the fractures open. 
     
     
         9 . The method of  claim 1 , further comprising providing heated injection fluid into at least one of the fractures. 
     
     
         10 . The method of  claim 1 , further comprising providing heated injection fluid into at least one of the fractures to provide at least some heat to the hydrocarbon containing layer. 
     
     
         11 . A method for treating a hydrocarbon containing layer in a subsurface formation, comprising:
 forming a plurality of substantially vertical fractures in the formation at selected intervals along lengths of a plurality of production wellbores positioned substantially horizontally in the hydrocarbon containing layer;   providing heat from a plurality of heaters to the hydrocarbon containing layer such that at least some hydrocarbons in the hydrocarbon containing layer are mobilized, wherein at least some of the plurality of heaters are positioned substantially horizontally in the hydrocarbon containing layer; and   producing at least some mobilized hydrocarbons through at least one of the production wellbores.   
     
     
         12 . The method of  claim 11 , further comprising forming the fractures at substantially equidistant intervals along the length of at least one of the production wellbores. 
     
     
         13 . The method of  claim 11 , wherein at least a portion of one of the fractures formed along at least one of the production wellbores overlaps with a portion of at least one of the fractures formed along an adjacent production wellbore. 
     
     
         14 . The method of  claim 11 , wherein the heaters are positioned in heater wellbores. 
     
     
         15 . The method of  claim 11 , wherein the heaters are positioned substantially parallel with the production wellbores. 
     
     
         16 . The method of  claim 11 , wherein the heaters are positioned substantially perpendicular to the production wellbores. 
     
     
         17 . The method of  claim 11 , wherein the fractures have oblong cross-sections. 
     
     
         18 . The method of  claim 11 , wherein at least one of the production wellbores is located closer to a bottom of the hydrocarbon containing layer than a top of the hydrocarbon containing layer. 
     
     
         19 . The method of  claim 11 , further comprising providing a proppant to keep one or more of the fractures open. 
     
     
         20 . The method of  claim 11 , further comprising providing heated injection fluid into at least one of the fractures. 
     
     
         21 . The method of  claim 11 , further comprising providing heated injection fluid into at least one of the fractures to provide at least some heat to the hydrocarbon containing layer. 
     
     
         22 . A system configured for treating a hydrocarbon containing layer in a subsurface formation, comprising:
 a plurality of production wellbores positioned substantially horizontally in the hydrocarbon containing layer;   a plurality of heaters positioned substantially horizontally in the hydrocarbon containing layer, wherein the heaters are configured to provide heat to the hydrocarbon containing layer such that at least some hydrocarbons in the hydrocarbon containing layer are mobilized during use; and   a plurality of substantially vertical fractures formed in the formation at selected intervals along a length of at least one of the production wellbores.   
     
     
         23 . The system of  claim 22 , wherein the heaters are positioned in heater wellbores. 
     
     
         24 . The system of  claim 22 , wherein the heaters are positioned substantially parallel with the production wellbores. 
     
     
         25 . The system of  claim 22 , wherein the heaters are positioned substantially perpendicular to the production wellbores. 
     
     
         26 . The system of  claim 22 , wherein the fractures have oblong cross-sections. 
     
     
         27 . The system of  claim 22 , wherein at least one of the production wellbores is located closer to a bottom of the hydrocarbon containing layer than a top of the hydrocarbon containing layer.