Pressure assisted oil recovery

Abstract

Estimates of global total “liquid” hydrocarbon resources are dominated by structures known as oil sands or tar sands which represent approximately two-thirds of the total recoverable resources. This is despite that the Canadian Athabasca Oil Sands, which dominate these oil sand based recoverable oil reserves at 1.7 trillion barrels, are calculated at only a 10% recovery rate. However, irrespective of whether it is the 3.6 trillion barrels recoverable from the oil sands or the 1.75 trillion barrels from conventional oil reservoirs worldwide, it is evident that significant financial return and extension of the time oil as resource is available to the world arise from increasing the recoverable percentage of such resources. According to embodiments of the invention pressure differentials are exploited to advance production of wells, adjust the evolution of the depletion chambers formed laterally between laterally spaced wells to increase the oil recovery percentage, and provide recovery in deeper reservoirs.

I claim: 
     
         1 . A method of altering and producing oil from an oil sand reservoir comprising:
 first and second well pairs separated by a predetermined separation, each well pair comprising: a first well within the oil sand reservoir, and a second well within the oil sand reservoir at a predetermined vertical offset to the first well, the second well being substantially parallel to the first well and the second well being at a predetermined lateral offset to the first well;   drilling an infill well within the oil sand reservoir at a predetermined location between the first and second well pairs at any time thereafter;   prior to any production, operating the first and second well pairs as steam assisted gravity drainage (SAGD) well pairs by selectively injecting a first fluid into at least the first well of each well pair according to a first predetermined schedule to create first zones of increased mobility within the oil sand reservoir around the first well of each well pair;   operating the infill well by contemporaneously injecting steam and producing an emulsion via the infill well until fluid communication is established between the infill well and at least one of the SAGD well pairs;   thereafter converting the infill well to dedicated production;   the fluid injected into the first well pair, the second well pair, and the infill well substantially altering the oil sands reservoir such that hydrocarbons contained in the oil sands composition are transformed into a mobile state allowing the hydrocarbons to be extracted from the oil sands reservoir; and substantially altering bitumen by separating in situ the bitumen from the reservoir solids and gasses.   
     
     
         2 . A method of altering and producing oil from an oil sand reservoir comprising:
 first and second well pairs separated by a predetermined separation, each well pair comprising: a first well within the oil sand reservoir, and a second well within the oil sand reservoir at a predetermined vertical offset to the first well, the second well being substantially parallel to the first well and the second well being at a predetermined lateral offset to the first well;   drilling an infill well within the oil sand reservoir at a predetermined location between the first and second well pairs at any time thereafter;   prior to any production, operating the first and second well pairs as steam assisted gravity drainage (SAGD) well pairs by selectively injecting a first fluid into at least the first well of each well pair according to a first predetermined schedule to create first zones of increased mobility within the oil sand reservoir around the first well of each well pair;   operating the infill well by alternating between injection and production until fluid communication is established between the infill well and at least one of the SAGD well pairs;   thereafter converting the infill well to dedicated production;   the fluid injected into the first well pair, the second well pair, and the infill well substantially altering the oil sands composition such that hydrocarbons contained in the oil sands composition are transformed into a mobile state allowing the hydrocarbons to be extracted from the oil sands reservoir; and substantially altering bitumen by separating in situ the bitumen from the reservoir solids and gasses.   
     
     
         3 . The method according to  claim 2  wherein the first well is an injection well. 
     
     
         4 . The method according to  claim 2  wherein the second and third wells are production wells. 
     
     
         5 . The method according to  claim 2  wherein the production wells are drilled from the same well pad and/or the same well bore. 
     
     
         6 . The method according to  claim 2  wherein the first injection well is associated with at least two production wells. 
     
     
         7 . The method of  claim 2  wherein the first, second and third wells comprise an array of first, second and third wells in a reservoir. 
     
     
         8 . The method according to  claim 2  wherein the fluid injected into the first well comprises at least one of steam, methane, propane, butane, solvent, non-condensable gas or condensable gas. 
     
     
         9 . A method of altering and producing oil from an oil sand reservoir comprising:
 a first well, a second well, and a third well within an oil sand reservoir, the second and third wells being at a zero vertical offset to the first well, the second the third also wells being substantially parallel to the first well, and the second and the third wells being at a predetermined lateral offset to the first well;
 operating the first and second and third wells substantially under steam assisted gravity drainage (SAGD) by selectively injecting a first fluid into at least the first well according to a first predetermined schedule to create a first zone of increased mobility within the oil sand reservoir around the first well; 
 the fluid injected into the first well generating oil miscibility through reservoir composition alteration. 
   
     
     
         10 . The method according to  claim 9  wherein each of the second and third wells is at a predetermined lateral offset to the first well, wherein the second well is laterally on one side of the first well and the third well is laterally on the other side of the first well. 
     
     
         11 . The method according to  claim 9  wherein the two production wells are drilled from the same well pad and or the same well bore.