Enhanced hydrocarbon recovery from multiple wells by electrical resistive heating of oil sand formations

Abstract

The present invention is a method and apparatus for enhanced recovery of petroleum fluids from the subsurface by electrical resistive heating of the oil sand formation and the heavy oil and bitumen in situ, by electrically energizing vertical inclusion planes containing electrically conductive proppant. The inclusion is propagated into a portion of the formation having a Skempton's B parameter of greater than 0.95 exp(−0.04 p′)+0.008 p′, where p′ is a mean effective stress in MPa at the depth of the inclusion. Multiple propped vertical inclusions at various azimuths are constructed from multiple wells. Electrodes are placed in the wells in electrical contact with the inclusions and an alternating direction current is passed through the proppant. By electrically resistive heating of the inclusion, the formation is heated by conduction and associated hydrocarbon fluids are lowered in viscosity and drain by gravity back to the well and produced to the surface. By controlling the reservoir temperature and pressure, a particular fraction of the in situ hydrocarbon reserve is extracted and water inflow into the heated zone is minimized.

1 . A method of improving production of hydrocarbons from a subterranean formation of weakly cemented sediments, the method comprising the steps of:
 a) propagating a substantially vertical first inclusion into the formation in a first preferential direction having an azimuth from a substantially vertical central wellbore intersecting the formation, wherein the first inclusion is filled with an injected fluid including electrically conductive proppant particles;   b) locating a circumferential relief wellbore on the azimuth aligned with the propagating first inclusion so that the first inclusion intersects the circumferential relief wellbore;   c) maintaining the circumferential relief wellbore at a reduced pressure;   d) passing an electric current through the first inclusion by electrodes placed in the central wellbore and in the circumferential relief wellbore and heating the formation in a process zone in the vicinity of the first inclusion; and   e) producing the heated hydrocarbons up the wellbores from the formation.   
     
     
         2 . The method of  claim 1 , wherein are the method includes propagating a plurality of first inclusions at varying azimuths and locating a plurality of circumferential relief wells aligned at the same varying azimuths and with the electric current passing through all inclusions from the central well to the circumferential wells. 
     
     
         3 . The method of  claim 1 , wherein a second inclusion is propagated from the central wellbore at a depth above the first inclusion after the viscosity of injected fluid in the first inclusion has substantially reduced so that the second inclusion intersects and coalesces with the first inclusion, and passing the electric current through the first and second inclusions. 
     
     
         4 . The method of  claim 3 , wherein the method further includes propagating a plurality of inclusions at varying azimuths and locating a plurality of circumferential wells aligned at the same varying azimuths and with the electric current passing through all inclusions from the central well to the circumferential wells. 
     
     
         5 . The method of  claim 1 , wherein the proppant particles range in size from #4 to #100 U.S. mesh and are ceramic beads substantially coated with an electrically conductive resin. 
     
     
         6 . The method of  claim 5 , wherein the resin is phenol formaldehyde containing fine graphite particles and is heat hardenable, with resin present in an amount sufficient to consolidate the proppant, but insufficient to fill the openings between the proppant. 
     
     
         7 . The method of  claim 1 , wherein the proppant particles range in size from #4 to #100 U.S. mesh and are selected from a group of conductive materials such as metals, melt alloys, metal oxides, metal salts, metal-containing catalysts, calcined petroleum coke or graphite beads, green or black silicon carbide, boron carbide or a mixture thereof. 
     
     
         8 . The method of  claim 1 , wherein the proppant particles range in size from #4 to #100 U.S. mesh and are selected from a group of non-conductive materials such as ceramics, glass and sands coated with a conductive layer either being metal, metal oxide, metal salts, conductive resins or mixtures thereof. 
     
     
         9 . The method of  claim 1 , wherein pressure in the majority of the heated process zone is held at ambient reservoir pressure by injecting into the process zone steam, non-condensing gas, or a hydrocarbon solvent in a vaporized state or a mixture thereof. 
     
     
         10 . The method of  claim 9 , wherein the solvent is one of a group of ethane, propane, butane or a mixture thereof. 
     
     
         11 . The method of  claim 9 , wherein the solvent is mixed with a diluent gas. 
     
     
         12 . The method of  claim 11 , wherein the diluent gas is non-condensable under the process conditions. 
     
     
         13 . The method of  claim 12 , wherein the non-condensable diluent gas has a lower solubility in the formation than the saturated hydrocarbon solvent. 
     
     
         14 . The method of  claim 13 , wherein the diluent gas is one of a group of methane, nitrogen, carbon dioxide, natural gas or a mixture thereof. 
     
     
         15 . The method of  claim 1 , wherein the method further includes injecting a hydrogenizing gas into the wellbore and thus into the fluids in the process zone to promote hydrogenation and thermal cracking reactions of at least a portion of the hydrocarbons in the process zone. 
     
     
         16 . The method of  claim 15 , wherein the hydrogenising gas consists of one of the group of H2 and CO or a mixture thereof. 
     
     
         17 . The method of  claim 15 , wherein catalyzing the hydrogenation and thermal cracking reactions involves at least a portion of the hydrocarbons in the process zone. 
     
     
         18 . The method of  claim 17 , wherein a metal-containing catalyst is used to catalyze said hydrogenation and thermal cracking reactions. 
     
     
         19 . The method of  claim 18 , wherein the catalyst is contained in a canister in tubing inside of the wellbore. 
     
     
         20 . The method of  claim 1 , wherein the proppant in the inclusions contains the catalyst for said hydrogenation and thermal cracking reactions. 
     
     
         21 . The method of  claim 3 , wherein the method includes propagating a plurality of second inclusions propagated from the central wellbore at progressively shallower depths above the first inclusion after the viscosity of injected fluid in the immediately lower inclusion has substantially reduced so that the plurality of second inclusions intersect and coalesces with each other and with the first inclusion, and passing the electric current through all of the inclusions. 
     
     
         22 . The method of  claim 1 , wherein a portion of the formation in which the first inclusion is formed has a Skempton B parameter greater than 0.95 exp(−0.04 p′)+0.008 p′, where p′ is a mean effective stress in MPa at the depth of the first inclusion and the water saturation in the formation pores is greater or equal to 10%. 
     
     
         23 . A hydrocarbon production well in a formation of unconsolidated and weakly cemented sediments having an ambient reservoir pressure and temperature comprising:
 a) a substantially vertical bore hole in the formation to a predetermined depth;   b) an injection casing grouted in the bore hole depth to create a substantially vertical central wellbore, the injection casing being radially expandable by the introduction of a fluid;   c) a vertical first inclusion in the formation created by the fluid delivered into the injection casing with sufficient pressure to dilate the injection casing and to create the first inclusion in the formation, wherein the first inclusion is filled with the fluid including electrically conductive proppant particles and wherein the first inclusion is oriented in the formation in a first preferential direction extending from and in communication with the substantially vertical wellbore;   d) a circumferential relief wellbore on the azimuth aligned with the first inclusion so that the first inclusion intersects the circumferential relief wellbore;   e) means for maintaining a reduced pressure in the circumferential relief wellbore;   f) electrodes placed in the central wellbore and the relief wellbore for passing an electric current through the inclusion for heating the formation in a process zone in the vicinity of the first inclusion and thereby producing the heated hydrocarbons up the wellbore from the formation.   
     
     
         24 . The production well of  claim 23 , wherein the production well further includes a plurality of first inclusions at varying azimuths and a plurality of circumferential relief wells aligned at the same varying azimuths and the electrodes pass the electric current through all inclusions from the central well to the circumferential wells. 
     
     
         25 . The production well of  claim 23 , wherein the production well further includes a second inclusion propagated from the central wellbore at a depth above the first inclusion after the viscosity of injected fluid in the first inclusion has substantially reduced so that the second inclusion intersects and coalesces with the first inclusion, and the electrodes pass the electric current through the first and second inclusions. 
     
     
         26 . The production well of  claim 25 , wherein the production well further includes a plurality of inclusions at varying azimuths and a plurality of circumferential wells aligned at the same varying azimuths and the electrodes pass the electric current through all inclusions from the central well to the circumferential wells. 
     
     
         27 . The production well of  claim 23 , wherein the proppant particles range in size from #4 to #100 U.S. mesh and are ceramic beads substantially coated with an electrically conductive resin. 
     
     
         28 . The production well of  claim 27 , wherein the resin is phenol formaldehyde containing fine graphite particles and is heat hardenable, with resin present in an amount sufficient to consolidate the proppant, but insufficient to fill the openings between the proppant. 
     
     
         29 . The production well of  claim 23 , wherein the proppant particles range in size from #4 to #100 U.S. mesh and are selected from a group of conductive materials such as metals, melt alloys, metal oxides, metal salts, metal-containing catalysts, calcined petroleum coke or graphite beads, green or black silicon carbide, boron carbide or a mixture thereof. 
     
     
         30 . The production well of  claim 23 , wherein the proppant particles range in size from #4 to #100 U.S. mesh and are selected from a group of non-conductive materials such as ceramics, glass and sands coated with a conductive layer either being metal, metal oxide, metal salts, conductive resins or mixtures thereof. 
     
     
         31 . The production well of  claim 23 , wherein pressure in the majority of the heated process zone is held at ambient reservoir pressure by injecting into the process zone steam, non-condensing gas, or a hydrocarbon solvent in a vaporized state or a mixture thereof. 
     
     
         32 . The production well of  claim 31 , wherein the solvent is one of a group of ethane, propane, butane or a mixture thereof. 
     
     
         33 . The production well of  claim 31 , wherein the solvent is mixed with a diluent gas. 
     
     
         34 . The method of  claim 33 , wherein the diluent gas is non-condensable under the process conditions. 
     
     
         35 . The production well of  claim 34 , wherein the non-condensable diluent gas has a lower solubility in the formation than the saturated hydrocarbon solvent. 
     
     
         36 . The production well of  claim 35 , wherein the diluent gas is one of a group of methane, nitrogen, carbon dioxide, natural gas or a mixture thereof. 
     
     
         37 . The production well of  claim 23 , wherein the production well further includes means for injecting a hydrogenizing gas into the wellbore and thus into the fluids in the process zone to promote hydrogenation and thermal cracking reactions of at least a portion of the hydrocarbons in the process zone. 
     
     
         38 . The production well of  claim 37 , wherein the hydrogenising gas consists of one of the group of H2 and CO or a mixture thereof. 
     
     
         39 . The production well of  claim 37 , wherein catalyzing the hydrogenation and thermal cracking reactions involves at least a portion of the hydrocarbons in the process zone. 
     
     
         40 . The production well of  claim 39 , wherein a metal-containing catalyst is used to catalyze said hydrogenation and thermal cracking reactions. 
     
     
         41 . The production well of  claim 40 , wherein the catalyst is contained in a canister in tubing inside of the wellbore. 
     
     
         42 . The production well of  claim 23 , wherein the proppant in the inclusions contains the catalyst for said hydrogenation and thermal cracking reactions. 
     
     
         43 . The production well of  claim 25 , wherein the production well includes a plurality of second inclusions propagated from the central wellbore at progressively shallower depths above the first inclusion after the viscosity of injected fluid in the immediately lower inclusion has substantially reduced so that the plurality of second inclusions intersect and coalesces with each other and with the first inclusion, and the electrodes pass the electric current through all of the inclusions. 
     
     
         44 . The production well of  claim 23 , wherein a portion of the formation in which the first inclusion is formed has a Skempton B parameter greater than 0.95 exp(−0.04 p′)+0.008 p′, where p′ is a mean effective stress in MPa at the depth of the first inclusion and the water saturation in the formation pores is greater or equal to 10%.