Radio-frequency enhancement and facilitation of in-situ combustion

Abstract

Radio frequency radiation is introduced downhole to heat one or more components of an in-situ hydrocarbon mixture. The mixture is heated to a temperature conducive to auto-ignition. Upon heating, an oxidant is introduced at conditions supportive of auto-ignition. The combined oxidant/hydrocarbon mixture is then allowed to auto-ignite and combust to form a partially upgraded mixture. Certain embodiments include introducing an ignition agent to facilitate auto-ignition. The radio frequency radiation may be supplemented, continued, or varied as desired to maintain, facilitate, or manage the resulting combustion process. In some cases, an activator is introduced to the formation to interact with the generated radio frequency radiation to enhance hydrocarbon heating. Advantages of certain embodiments include lower cost, reduced heating/ignition equipment, higher efficiencies, increased hydrocarbon recovery, and fewer auto-ignition failures.

What is claimed is: 
     
         1 . A method for facilitating in-situ combustion of an in-situ hydrocarbon mixture using a generated radio frequency radiation comprising the steps of:
 introducing one or more activators into a subterranean formation;   introducing the generated radio frequency radiation into the subterranean formation, wherein the generated radio frequency radiation is from about 0.1 MHz to about 1 GHz;   introducing an ignition agent into the subterranean formation;   allowing the generated radio frequency radiation to heat the one or more activators;   allowing the activators to heat the in-situ hydrocarbons by conductive heating to a first temperature that is supportive of auto-ignition of the in-situ hydrocarbon mixture, wherein the generated radio frequency radiation is from about 0.1 MHz to about 1 GHz;   introducing an oxidant into the subterranean formation to form a combined mixture of oxidant and in-situ hydrocarbon mixture;   allowing the combined mixture of the oxidant and the in-situ hydrocarbon mixture to auto-ignite; and   allowing the combined mixture to combust through a combustion process to form a second in-situ hydrocarbon mixture.   
     
     
         2 . The method of  claim 1  wherein the one or more activators is a metal containing compound from period 3 or period 4 of the Periodic Table, a halide of Na, Al, Fe, Ni, or Zn, including AlCl 4   − , FeCl 4   − , NiCl 3   − , ZnCl 3   − , transitional metal compounds, organometallic complexes, or any combination thereof. 
     
     
         3 . The method of  claim 1  wherein the one or more activators comprise a first activator and a second activator wherein the first activator has a first optimal excitation frequency and wherein the second activator has a second optimal excitation frequency. 
     
     
         4 . The method of  claim 3  wherein the generated radio frequency radiation comprises the first optimal excitation frequency and the second optimal excitation frequency. 
     
     
         5 . The method of  claim 3  wherein the generated radio frequency radiation varies in frequency through a frequency range that includes both the first optimal excitation frequency and the second optimal excitation frequency. 
     
     
         6 . The method of  claim 1  wherein the ignition agent is tung oil, linseed oil, red oil, castor oil, turpentine, tall oil, a fatty acid of tall oil, oleic acid, a fatty acid of linseed oil, diesel oil, magnesium powder, light naptha, any combination thereof. 
     
     
         7 . The method of  claim 1  wherein the ignition agent comprises a combustion catalyst wherein the combustion catalyst is cobalt naphthenate, cobalt tallate, cobalt octoate, or any combination thereof. 
     
     
         8 . The method of  claim 1  wherein the ignition agent comprises an aliphatic compound that comprises at least 16 carbon atoms per molecule. 
     
     
         9 . The method of  claim 8  wherein the aliphatic compound is linoleyl alcohol, linoleic acid, eleostearic acid, eleostearyl alcohol, ricinoleic alcohol, clupadonyl alcohol, clupadonic acid, or any combination thereof. 
     
     
         10 . The method of  claim 1  wherein the ignition agent is a pyrophoric compound wherein the pyrophoric compound is an oxidizable lower alkyl derivatives of boron or zinc described by (R1) 3 B, R1 R2 R3Al, and R4 R5Zn, where R1 is C1 to C3 alkyl group and R2 to R5 are C1 to C4 alkyl groups. 
     
     
         11 . The method of  claim 1  wherein the ignition agent is an aqueous colloidal suspension of metallic magnesium. 
     
     
         12 . A method for facilitating in-situ combustion of an in-situ hydrocarbon mixture using a generated radio frequency radiation comprising the steps of:
 introducing the generated radio frequency radiation into a subterranean formation;   allowing the generated radio frequency radiation to heat one or more components of the in-situ hydrocarbon mixture to a first temperature that is supportive of auto-ignition of the in-situ hydrocarbon mixture, wherein the generated radio frequency radiation is from about 0.1 MHz to about 1 GHz;   introducing an ignition agent into the subterranean formation;   introducing an oxidant into the subterranean formation to form a combined mixture of oxidant and in-situ hydrocarbon mixture;   allowing the combined mixture of the oxidant and the in-situ hydrocarbon mixture to auto-ignite; and   allowing the combined mixture to combust through a combustion process to form a second in-situ hydrocarbon mixture.   
     
     
         13 . The method of  claim 12  wherein the generated radio frequency radiation is from about 300 MHz to about 1 GHz. 
     
     
         14 . The method of  claim 12  wherein the oxidant is air, an oxygen-enriched mixture, a gas mixture comprising oxygen, or any combination thereof. 
     
     
         15 . The method of  claim 12  further comprising the step of upgrading a plurality of the components of the in-situ hydrocarbon mixture. 
     
     
         16 . The method of  claim 12  wherein the in-situ hydrocarbon mixture has a first viscosity and wherein the second in-situ hydrocarbon mixture has a second viscosity, and wherein the method of  claim 12  further comprises the step of allowing the combustion process to produce the second in-situ hydrocarbon mixture with a second viscosity that is lower than the first viscosity. 
     
     
         17 . The method of  claim 12  further comprising the step of producing a portion of the second hydrocarbon mixture. 
     
     
         18 . The method of  claim 12  further comprising the step of introducing an upgrading catalyst into the subterranean formation before the step of allowing the combined mixture of oxidant and the in-situ hydrocarbon mixture to auto-ignite. 
     
     
         19 . The method of  claim 13  wherein the step of introducing the generated radio frequency radiation into the subterranean formation occurs at a second well and wherein the step of producing the portion of the second hydrocarbon mixture occurs at a first well. 
     
     
         20 . The method of  claim 12  further comprising the step of determining an optimal frequency for the generated radio frequency radiation to achieve the auto-ignition temperature of the combined mixture, wherein the optimal frequency maximizes overall heat input to the in-situ hydrocarbon mixture, wherein the generated radio frequency radiation is within about 10% of the optimal frequency. 
     
     
         21 . The method of  claim 12  wherein the in-situ hydrocarbon mixture and the second hydrocarbon mixture are each non-homogenous mixtures. 
     
     
         22 . The method of  claim 12  further comprising the step of introducing a second generated radio frequency radiation into the subterranean formation, after the step of allowing the combined mixture to combust, to maintain the combustion process. 
     
     
         23 . The method of  claim 12  wherein the ignition agent is tung oil, linseed oil, red oil, castor oil, turpentine, tall oil, a fatty acid of tall oil, oleic acid, a fatty acid of linseed oil, diesel oil, magnesium powder, light naptha, any combination thereof. 
     
     
         24 . The method of  claim 12  wherein the ignition agent comprises a combustion catalyst wherein the combustion catalyst is cobalt naphthenate, cobalt tallate, cobalt octoate, or any combination thereof. 
     
     
         25 . The method of  claim 12  wherein the ignition agent is an aliphatic compound comprising at least 16 carbon atoms per molecule. 
     
     
         26 . The method of  claim 25  wherein the aliphatic compound is linoleyl alcohol, linoleic acid, eleostearic acid, eleostearyl alcohol, ricinoleic alcohol, clupadonyl alcohol, clupadonic acid, or any combination thereof. 
     
     
         27 . The method of  claim 12  wherein the ignition agent is a pyrophoric compound wherein the pyrophoric compound is an oxidizable lower alkyl derivatives of boron or zinc described by (R1) 3 B, R1 R2 R3Al, and R4 R5Zn, where R1 is C1 to C3 alkyl group and R2 to R5 are C1 to C4 alkyl groups. 
     
     
         28 . The method of  claim 12  wherein the ignition agent is an aqueous colloidal suspension of metallic magnesium.