Systems and Methods For Pressure-Cycled Stimulation During Gravity Drainage Operations

Abstract

Systems and methods for pressure-cycled stimulation during gravity drainage operations. These systems and methods include increasing a pressure within a stimulation well that extends within a subterranean formation and subsequently decreasing the pressure within the stimulation well to increase production of viscous hydrocarbons from a production well. The systems and methods include repeating the increasing and the decreasing for a plurality of stimulation cycles and producing viscous hydrocarbons from the subterranean formation during the increasing, the decreasing, and the repeating. The increasing may include increasing a reservoir pressure within the subterranean formation to a pressure that is greater than a bubble point pressure of the viscous hydrocarbons, and the decreasing may include decreasing the reservoir pressure to a pressure that is less than the bubble point pressure of the viscous hydrocarbons.

1 . A method of stimulating and producing viscous hydrocarbons from a subterranean formation that includes the viscous hydrocarbons, the method comprising:
 increasing a pressure within a stimulation well that extends within the subterranean formation to increase a reservoir pressure to a pressure that is above an upper pressure threshold that is greater than a bubble point pressure of the viscous hydrocarbons;   decreasing the pressure within the stimulation well to decrease the reservoir pressure to a pressure that is below a lower pressure threshold that is less than the bubble point pressure of the viscous hydrocarbons;   repeating the increasing the pressure and the decreasing the pressure for a plurality of stimulation cycles; and   producing, as a reduced viscosity hydrocarbon stream, the viscous hydrocarbons from a production well that extends within the subterranean formation and is spaced apart from the stimulation well, wherein the producing includes producing during the increasing the pressure, the decreasing the pressure, and the repeating, and wherein the production well is spaced-apart from the stimulation well.   
     
     
         2 . The method of  claim 1 , wherein the increasing the pressure includes providing a stimulant fluid stream to the stimulation well. 
     
     
         3 . The method of  claim 2 , wherein the providing a stimulant fluid stream includes controlling a flow rate of the stimulant fluid stream to control a rate of the increasing by at least one of:
 (i) increasing the flow rate of the stimulant fluid stream responsive to the rate of the increasing being less than a threshold lower increasing rate; and   (ii) decreasing the flow rate of the stimulant fluid stream responsive to the rate of the increasing being greater than a threshold upper increasing rate.   
     
     
         4 . The method of  claim 1 , wherein, subsequent to the increasing the pressure and prior to the decreasing the pressure, the method further comprises maintaining the reservoir pressure above the upper pressure threshold for at least a threshold pressurized time. 
     
     
         5 . The method of  claim 4 , wherein the increasing includes providing a stimulant fluid stream to the stimulation well at a first flow rate, and wherein the maintaining the reservoir pressure above the upper pressure threshold includes providing the stimulant fluid stream to the stimulation well at a second flow rate. 
     
     
         6 . The method of  claim 4 , wherein the maintaining includes controlling a flow rate of a stimulant fluid stream to maintain the reservoir pressure above the upper pressure threshold. 
     
     
         7 . The method of  claim 4 , wherein the threshold pressurized time is at least 1 day and less than 500 days. 
     
     
         8 . The method of  claim 4 , further comprising preserving a fluid temperature difference between a stimulant fluid stream and the reduced viscosity hydrocarbon stream below a threshold fluid temperature difference during the maintaining. 
     
     
         9 . The method of  claim 1 , wherein the decreasing the pressure includes at least one of ceasing providing a stimulant fluid stream to the stimulation well and decreasing a flow rate of the stimulant fluid stream to the stimulation well. 
     
     
         10 . The method of  claim 1 , wherein the decreasing the pressure includes liberating a solution gas from the viscous hydrocarbon while the viscous hydrocarbon is present within the subterranean formation. 
     
     
         11 . The method of  claim 1 , wherein, subsequent to the decreasing the pressure, the method further comprises maintaining the reservoir pressure below the lower pressure threshold for at least a threshold depressurized time, wherein the threshold depressurized time is at least 1 day and less than 250 days. 
     
     
         12 . The method of  claim 1 , wherein the repeating includes repeating the increasing and the decreasing for at least 10 stimulation cycles. 
     
     
         13 . The method of  claim 1 , wherein the repeating includes performing the increasing the pressure and subsequently performing the decreasing the pressure in each stimulation cycle of the plurality of stimulation cycles. 
     
     
         14 . The method of  claim 1 , wherein the producing includes continuously producing the viscous hydrocarbons during at least 90% of a time period during which the increasing the pressure, the decreasing the pressure, and the repeating occurs. 
     
     
         15 . The method of  claim 1 , further comprising monitoring the reservoir pressure. 
     
     
         16 . The method of  claim 15 , wherein the decreasing the pressure includes decreasing the pressure based, at least in part, on determining that the reservoir pressure is greater than the upper pressure threshold. 
     
     
         17 . The method of  claim 15 , wherein the increasing the pressure includes increasing the pressure based, at least in part, on determining that the reservoir pressure is less than the lower pressure threshold. 
     
     
         18 . The method of  claim 15 , wherein the monitoring the reservoir pressure includes calculating the reservoir pressure. 
     
     
         19 . The method of  claim 1 , wherein the producing further comprises producing the viscous hydrocarbons from the production well for a pre-production time prior to at least the decreasing the pressure and the repeating. 
     
     
         20 . The method of  claim 1 , further comprising performing the method as part of at least one of a steam-assisted gravity drainage process, a solvent-assisted steam-assisted gravity drainage process, and a vapor extraction process. 
     
     
         21 . A system configured to produce viscous hydrocarbons from a subterranean formation, the system comprising:
 a stimulation well that extends within the subterranean formation;   a stimulant fluid supply system that is configured to provide a stimulant fluid stream to the subterranean formation via the stimulation well;   a production well that is spaced-apart from the stimulation well, extends within the subterranean formation, and is configured to produce a reduced viscosity hydrocarbon stream from the subterranean formation; and   a controller that is programmed to control the operation of the system using the method of  claim 1 .