Mitigating thief zone losses by thief zone pressure maintenance through downhole radio frequency radiation heating

Abstract

Methods are provided for mitigating thief zone losses during hydrocarbon recovery by thief zone pressure maintenance through downhole radio frequency (RF) radiation heating. A thief zone situated near a hydrocarbon reservoir poses a risk of losing valuable components from the reservoir to the thief zone. In addition to the risk of loss of diluent, heat, or steam to the thief zone, valuable hydrocarbons may also be lost to the thief zone. One way to mitigate these losses is by maintaining thief zone pressure. RF radiation may be used to heat a thief zone fluid to maintain pressure in the thief zone, decreasing the driving force for losses to the thief zone. In some cases, steam generated thusly may be used to enhance hydrocarbon thermal recovery. Advantages of methods herein include: lower costs, higher efficiencies, higher hydrocarbon recovery, less hydrocarbon contamination, increased hydrocarbon mobility, and fewer thief zone losses.

What is claimed is: 
     
         1 . A method for mitigating thief zone losses during heavy oil recovery by thief zone pressure maintenance through downhole radio frequency radiation heating comprising the steps of:
 introducing a steam assisted gravity drainage (SAGD) well pair into a subterranean formation, wherein the SAGD well pair comprises a producing well and a steam injection well, wherein subterranean formation comprises a hydrocarbon reservoir wherein the hydrocarbon reservoir comprises hydrocarbons;   introducing steam into the steam injection well to establish a steam chamber in the hydrocarbon reservoir;   introducing an antenna into the subterranean formation, wherein the antenna is operable connected to an energy source, wherein the subterranean formation comprises a thief zone, wherein the thief zone is in thermal communication, fluid communication, or both with the steam chamber, wherein the thief zone comprises water;   inducing radio frequency radiation in the antenna by way of the energy source;   allowing the radio frequency radiation to propagate into the thief zone to heat at least a portion of the water therein to form steam to increase the pressure in the thief zone from a first thief zone pressure to a second thief zone pressure, wherein the second thief zone pressure mitigates or eliminates hydrocarbon or heat losses to the thief zone that would otherwise occur if the thief zone had remained at the first thief zone pressure; and   producing the hydrocarbons from the hydrocarbon reservoir through the producing well.   
     
     
         2 . The method of  claim 1  wherein the step of inducing radio frequency radiation in the antenna generates radio frequency radiation at a frequency from about 30 kHz to about 300 GHz. 
     
     
         3 . The method of  claim 1  wherein the hydrocarbons are bitumen. 
     
     
         4 . The method of  claim 1  wherein the thief zone is situated in an overburden of the hydrocarbon reservoir. 
     
     
         5 . The method of  claim 1  wherein the thief zone is situated in the hydrocarbon reservoir. 
     
     
         6 . The method of  claim 1  wherein the thief zone is a depleted steam chamber in the hydrocarbon reservoir. 
     
     
         7 . The method of  claim 1  wherein the antenna is situated above the hydrocarbon reservoir and wherein the antenna intersects the thief zone. 
     
     
         8 . A method for mitigating thief zone losses by thief zone pressure maintenance through downhole radio frequency radiation heating comprising the steps of:
 introducing an antenna into a subterranean formation, wherein the antenna is operable connected to an energy source, wherein the subterranean formation comprises a hydrocarbon reservoir and a thief zone, wherein the thief zone is in thermal communication, fluid communication, or both with the hydrocarbon reservoir, wherein the hydrocarbon reservoir comprises hydrocarbons, and wherein the thief zone comprises a thief zone fluid susceptible to heating from radio frequency radiation;   inducing radio frequency radiation in the antenna by way of the energy source;   allowing the radio frequency radiation to propagate into the thief zone to heat at least a portion of the thief zone fluid therein to vaporize the thief zone fluid to form a thief zone gas to increase the pressure in the thief zone from a first thief zone pressure to a second thief zone pressure, wherein the second thief zone pressure mitigates fluid or heat interaction between the thief zone and the hydrocarbon reservoir that would otherwise occur if the thief zone had remained at the first thief zone pressure; and   producing the hydrocarbons from the hydrocarbon reservoir.   
     
     
         9 . The method of  claim 8  wherein the step of producing the hydrocarbons comprises the step of recovering the hydrocarbons by way of a thermal recovery process. 
     
     
         10 . The method of  claim 9  wherein the thermal recovery process is a steam assisted gravity drainage (SAGD) process, a cyclic steam stimulation, a vapor extraction, a J-well SAGD, in situ combustion, a high pressure air injection, an expanding solvent-SAGD, a cross-SAGD process, or a combination thereof. 
     
     
         11 . The method of  claim 9  wherein the thief zone fluid comprises water and wherein the thief zone gas comprises steam. 
     
     
         12 . The method of  claim 11  further comprising the step of:
 determining an optimum excitation frequency of the radio frequency radiation by determining which frequency of the radio frequency radiation optimizes the thermal recovery process based on a depth of radio frequency penetration, a heat absorption of the radio frequency radiation, and an overall heat input by the radio frequency radiation at a given frequency; 
 wherein the step of inducing radio frequency radiation in the antenna generates radio frequency radiation at the optimal excitation frequency.