Method for removing bitumen to enhance formation permeability

Abstract

Treatment methods and treatment fluids for increasing permeability of organic shale formations are described herein. The treatment method includes treating an organic shale formation with a treatment fluid. The treatment fluid includes a solvent that dissolves bitumen in the shale formation. After treating the shale formation with the treatment fluid, oil is recovered from the shale formation. By removing bitumen from pores and pore throats within the formation, the solvent increases permeability of the formation and allows mobile oil to flow more easily through the formation.

What is claimed is: 
     
       1. A method for treating an organic shale formation to increase permeability and recover oil, the method comprising:
 using a wellbore that traverses the organic shale formation to treat at least a portion of the shale formation with a treatment fluid by injecting the treatment fluid into the portion of the shale formation in order to hydraulically fracture the portion of the organic shale formation, wherein the treatment fluid comprises an emulsification of a solvent that dissolves bitumen in the shale formation and increases permeability of the shale formation, a surfactant having a hydrophilic-lipophilic balance (HLB) value of between 10.5 and 18, and a diluent; and 
 after said injecting, recovering oil from the shale formation through said wellbore. 
 
     
     
       2. The method of  claim 1 , wherein the solvent comprises one of a terpene-based solvent, a limonene-based solvent, a pinene-based solvent, or a combination thereof. 
     
     
       3. The method of  claim 1 , wherein the solvent comprises one of cyclohexanone, N-methylpyrrolidinone, an aromatic fluid, a dialkyl ether, an alkylated fatty acid, a fatty acid alkyl ester, an alkenoic acid ester, 2-methyltetrahydrofuran, or a combination thereof. 
     
     
       4. The method of  claim 1 , wherein the solvent comprises one of a limonene-based solvent, a pinene-based solvent, cyclohexanone, N-methylpyrrolidinone, an aromatic fluid, a dialkyl ether, an alkylated fatty acid, a fatty acid alkyl ester, an alkenoic acid ester, 2-methyltetrahydrofuran, or a combination thereof. 
     
     
       5. The method of  claim 1 , wherein the diluent comprises one of water and a gas-based foam. 
     
     
       6. The method of  claim 1 , wherein a portion of the shale formation that is between 100 meters and 1000 meters away from the wellbore is treated with solvent. 
     
     
       7. The method of  claim 1 , wherein the bitumen is naturally-occurring bitumen within the formation. 
     
     
       8. The method of  claim 1 , wherein the shale formation comprises kerogen, bitumen, and a mobile oil. 
     
     
       9. The method of  claim 1 , further comprising:
 prior to said injecting, recovering oil from the portion of the organic shale formation. 
 
     
     
       10. The method of  claim 1 , further comprising:
 heating the treatment fluid to a temperature of 150° C. before said injecting treatment fluid into the portion of the shale formation. 
 
     
     
       11. The method of  claim 1 , wherein the solvent does not include xylene. 
     
     
       12. A method for treating an organic shale formation to increase permeability and recover oil, the method comprising:
 using a wellbore that traverses the organic shale formation to treat at least a portion of the shale formation with a treatment fluid by injecting the treatment fluid into the portion of the shale formation wherein the treatment fluid comprises an emulsification of a solvent that dissolves bitumen in the shale formation and increases permeability of the shale formation, a surfactant having a hydrophilic-lipophilic balance (HLB) value of between 10.5 and 18, and a diluent; 
 after said injecting the treatment fluid into the portion of the organic shale formation, hydraulically fracturing the portion of the formation; and 
 after said hydraulically fracturing, recovering oil from the shale formation through said wellbore. 
 
     
     
       13. The method of  claim 12 , wherein the solvent comprises one of a terpene-based solvent, a limonene-based solvent, a pinene-based solvent, or a combination thereof. 
     
     
       14. The method of  claim 12 , wherein the solvent comprises one of cyclohexanone, N-methylpyrrolidinone, an aromatic fluid, a dialkyl ether, an alkylated fatty acid, a fatty acid alkyl ester, an alkenoic acid ester, 2-methyltetrahydrofuran, or a combination thereof. 
     
     
       15. The method of  claim 12 , wherein the solvent comprises one of a limonene-based solvent, a pinene-based solvent, cyclohexanone, N-methylpyrrolidinone, an aromatic fluid, a dialkyl ether, an alkylated fatty acid, a fatty acid alkyl ester, an alkenoic acid ester, 2-methyltetrahydrofuran, or a combination thereof. 
     
     
       16. The method of  claim 12 , wherein the diluent comprises one of water and a gas-based foam. 
     
     
       17. The method of  claim 12 , wherein a portion of the shale formation that is between 100 meters and 1000 meters away from the wellbore is treated with solvent. 
     
     
       18. The method of  claim 12 , further comprising:
 prior to said injecting, recovering oil from the portion of the organic shale formation. 
 
     
     
       19. The method of  claim 12 , further comprising:
 heating the treatment fluid to a temperature of 150° C. before said injecting treatment fluid into the portion of the shale formation. 
 
     
     
       20. The method of  claim 12 , wherein the solvent does not include xylene.