Enhanced hydrocarbon recovery from low mobility reservoirs

Abstract

Methods are provided using heated fluids along with combined/drive cyclical injection/production profiles to enhance hydrocarbon recovery from shallow and/or low mobility reservoirs. In certain embodiments, injection and production flow rates to and from the reservoir are varied to beneficially modulate certain pressure drive profiles between a minimum pressure and a maximum pressure. During these drive profile modulations, heated water, solvent, and surfactant are injected into the reservoir. The combination of injected fluids and cyclical pressure drive profiles beneficially enhances hydrocarbon recovery from the reservoir. Other optional variations include using multiple injection and/or production wells. Advantages include accelerated hydrocarbon recovery, higher production efficiencies, and lower costs. These advantages ultimately translate to higher production and/or reduction of total hydrocarbon extraction time. These methods are particularly advantageous when applied to shallow reservoirs (e.g. reservoirs having depths less than or equal to about 150 meters).

1 . A method for enhancing hydrocarbon recovery from a low mobility reservoir having an injection well and a production well intersecting the low mobility reservoir, the method comprising the steps of:
 (a) providing water;   (b) providing a solvent;   (c) providing a surfactant;   (d) heating at least one of the water, the solvent, and the surfactant to its saturation temperature;   (e) introducing the water, the solvent and the surfactant into the low mobility reservoir at an injection rate by way of the injection well;   (f) allowing the pressure of the low mobility reservoir to increase until reaching a first maximum pressure of the low mobility reservoir;   (g) upon substantially reaching the first maximum pressure of the low mobility reservoir, producing from the production well at a production rate;   (h) allowing the reservoir pressure to reduce until the low mobility reservoir reaches a first minimum pressure;   (i) upon reaching the first minimum pressure, substantially reducing production from the production well; and   (j) repeating steps (e)-(i) a plurality of times.   
     
     
         2 . The method of  claim 1 :
 wherein step (d) comprises heating the water to its saturation temperature;   wherein the first maximum pressure is a dilation pressure of the low mobility reservoir;   wherein step (f) comprises the step of continuously increasing the pressure of the low mobility reservoir until reaching a dilation pressure of the low mobility reservoir in step (f);   wherein the production rate is substantially equal to or greater than the injection rate during step (h); and   wherein the first minimum pressure is a pre-determined pressure below the dilation pressure.   
     
     
         3 . The method of  claim 2  further comprising combining the water, the solvent, and the surfactant to produce an injection fluid wherein step (e) further comprises introducing the injection fluid into the low mobility reservoir at the injection rate by way of the injection well. 
     
     
         4 . The method of  claim 2  wherein step (i) further comprises substantially ceasing production from the production well. 
     
     
         5 . The method of  claim 2  wherein step (i) further comprises continuing step (i) during steps (f)-(i). 
     
     
         6 . The method of  claim 4  further comprising the step of substantially ceasing step (e) upon substantially reaching the dilation pressure of the low mobility reservoir. 
     
     
         7 . The method of  claim 2  wherein the production rate is substantially equal to the injection rate during step (h). 
     
     
         8 . The method of  claim 2  wherein the first minimum pressure is the minimum lifting pressure of the low mobility reservoir. 
     
     
         9 . The method of  claim 1  wherein the low mobility reservoir is a shallow reservoir having a depth of about 80 meters to about 150 meters and wherein the low mobility reservoir is unconsolidated. 
     
     
         10 . The method of  claim 9  wherein the first minimum pressure is from about 130 psi to about 250 psi. 
     
     
         11 . The method of  claim 2  wherein the low mobility reservoir is a shallow reservoir having a depth of about 80 meters to about 150 meters, wherein the first minimum pressure is from about 130 psi to about 250 psi. 
     
     
         12 . The method of  claim 11  wherein the solvent is wherein the solvent is carbon dioxide, flue gas, an aliphatic hydrocarbon having 4 carbons to 30 carbons, naptha, syncrude, diesel, an aromatic solvent, toluene, benzene, xylene, or any combination thereof. 
     
     
         13 . The method of  claim 11  wherein the surfactant is petroleum sulfonates, alph olefin sulfonates, synthetic alkylaryl sulfonates, or any combination thereof. 
     
     
         14 . The method of  claim 11  wherein the heated solvent has not been heated beyond its saturation temperature at the pressure of the low mobility reservoir. 
     
     
         15 . The method of  claim 14  wherein the heated solvent has been heated to a temperature that is less than its saturation temperature at the pressure of the low mobility reservoir. 
     
     
         16 . A method for enhancing hydrocarbon recovery from a low mobility reservoir having one or more injection wells and one or more production wells intersecting the low mobility reservoir, the method comprising the steps of:
 (a) providing water;   (b) providing a solvent;   (c) providing a surfactant;   (d) heating at least one of the water, the solvent, and the surfactant to its saturation temperature;   (e) introducing the water, solvent and the surfactant into the low mobility reservoir at a total injection rate by way of the one or more injection wells;   (f) allowing the pressure of the low mobility reservoir to increase until reaching a dilation pressure of the low mobility reservoir;   (g) upon substantially reaching the dilation pressure of the low mobility reservoir, producing from the one or more production wells at a total production rate;   (h) allowing the reservoir pressure to reduce until the low mobility reservoir reaches a first minimum pressure;   (i) upon reaching the first minimum pressure, substantially reducing production from the one or more production wells; and   (j) repeating steps (e)-(i) a plurality of times.   
     
     
         17 . The method of  claim 16  wherein the one or more injection wells comprises a plurality of injection wells. 
     
     
         18 . The method of  claim 17 :
 wherein step (f) comprises the step of continuously increasing the pressure of the low mobility reservoir until reaching a dilation pressure of the low mobility reservoir in step (f);   wherein step (d) further comprises heating the water;   wherein the total production rate is substantially equal to the total injection rate during step (h); and   wherein the first minimum pressure is a pre-determined pressure below the dilation pressure.   
     
     
         19 . The method of  claim 16  wherein the one or more production wells comprises a plurality of production wells. 
     
     
         20 . The method of  claim 17  wherein the one or more production wells comprises a plurality of production wells. 
     
     
         21 . The method of  claim 20 :
 wherein step (f) comprises the step of continuously increasing the pressure of the low mobility reservoir until reaching a dilation pressure of the low mobility reservoir in step (f);   wherein step (d) further comprises heating the water;   wherein the total production rate is substantially equal to the total injection rate during step (h); and   wherein the first minimum pressure is a pre-determined pressure below the dilation pressure.   
     
     
         22 . The method of  claim 21  wherein step (i) further comprises substantially ceasing production from the one or more production wells.