Miscible stimulation and flooding of petroliferous formations utilizing viscosified oil-based fluids

Abstract

A viscosified miscible enhanced oil recovery fluid includes (a) a hydrocarbon fluid and viscosifying agent, wherein the viscosified fluid is a Newtonian fluid, (b) a hydrocarbon fluid and gelling agent, wherein the viscosified fluid is a power law fluid, (c) a hydrocarbon fluid, a gelling agent, and a rheological additive, wherein the viscosified fluid is a yield power law fluid, or (d) a hydrocarbon fluid, a gelling agent, a rheological additive, and solvent for the rheological additive, wherein the viscosified fluid is a yield power law fluid. The hydrocarbon fluid is preferably weighted with nano-scale weighting agents. The viscosified fluids are prepared and pumped into a subterranean petroliferous formation to recover a majority of the oil, heavy oil, condensate, or gas originally in place. A method for subsequently recovering a substantial fraction of the miscible injectant conventionally or by applying a viscosity breaker and recovering the viscosity-broken miscible injectant conventionally.

1 . A viscosified miscible enhanced oil recovery fluid for injection into a subterranean petroliferous formation comprising:
 a weighted hydrocarbon-based fluid comprising a nano-scale weighting agent dispersed in a hydrocarbon-based fluid, and   at least one additive selected from the group consisting of viscosifying agents, gelling agents and rheological agents,   wherein said viscosified miscible enhanced oil recovery fluid has fluid behavior characteristics selected from the group consisting of yield power law fluids, power law fluids, Bingham-plastic fluids and Newtonian fluids.   
     
     
         2 . The viscosified fluid of  claim 1 , wherein said nano-scale weighting agent comprises at least one of barium sulfate, barium carbonate, zinc oxide, zinc nitride, magnesium oxide, or iron oxide. 
     
     
         3 . The viscosified fluid of  claim 1 , wherein said nano-scale weighting agent comprises a nano-scale-zinc-oxide. 
     
     
         4 . The viscosified fluid of  claim 1 , wherein said gelling agent comprises a multivalent metal ion and at least one ester selected from the group consisting of a phosphoric acid ester and a phosphonic acid ester. 
     
     
         5 . The viscosified fluid of  claim 4 , wherein said multivalent metal ion is at least one selected from the group consisting of a ferric ion, an aluminum ion, a chelated ferric ion and a chelated aluminum ion. 
     
     
         6 . The viscosified fluid of  claim 1 , wherein said rheological agent is an alkyl diamide having a formula: R 1 —HN—CO—(CH 2 ) n —CO—NH—R 2 , wherein n is an integer from 1 to 20, R 1  is an alkyl groups having from 1 to 20 carbons, and R 2  is hydrogen or an alkyl group having from 1 to 20 carbons. 
     
     
         7 . The viscosified fluid of  claim 1 , wherein said rheological agent is present at a concentration of 3-13 pounds per barrel. 
     
     
         8 . The viscosified fluid of  claim 1 , further comprising a solvent for said rheological agent. 
     
     
         9 . The viscosified fluid of  claim 1 , wherein said hydrocarbon-based fluid comprises at least one selected from diesel, a mixture of diesels and paraffin oil, mineral oil, and isomerized olefins. 
     
     
         10 . The viscosified fluid of  claim 1 , wherein said at least one additive comprises a viscosifying agent. 
     
     
         11 . The viscosified fluid of  claim 1 , wherein said at least one additive comprises a gelling agent. 
     
     
         12 . The viscosified fluid of  claim 1 , wherein said at least one additive comprises a gelling agent and a rheological agent. 
     
     
         13 . The viscosified fluid of  claim 1 , wherein said at least one additive comprises a gelling agent, a rheological agent and a solvent for said rheological agent. 
     
     
         14 . A method for preparing a viscosified miscible enhanced oil recovery fluid for injection into a subterranean petroliferous formation comprising the steps of:
 preparing a mixture of a weighted hydrocarbon-based fluid comprising a nano-scale weighting agent dispersed in a hydrocarbon-based fluid and at least one additive selected from the group consisting of viscosifying agents, gelling agents and rheological agents;   optionally heating said mixture to a selected temperature; and   optionally shearing said mixture,   wherein said mixture has fluid behavior characteristics selected from the group consisting of yield power law fluids, power law fluids, Bingham-plastic fluids and Newtonian fluids.   
     
     
         15 . A method for enhanced oil recovery from a subterranean petroliferous formation comprising the steps of:
 preparing a viscosified miscible enhanced oil recovery fluid comprising: a mixture of (a) a weighted hydrocarbon-based fluid comprising a nano-scale weighting agent dispersed in said hydrocarbon-based fluid, and (b) at least one additive selected from the group consisting of viscosifying agents, gelling agents and rheological agents; and   pumping said fluid mixture from the surface into said subterranean petroliferous formation;   wherein said viscosified miscible enhanced oil recovery fluid exhibits fluid behavior characteristics selected from the group consisting of yield power law fluid characteristics, power law fluid characteristics, Bingham-plastic fluid characteristics, and Newtonian fluid characteristics.   
     
     
         16 . The method of  claim 15 , wherein said nano-scale weighting agent comprises at least one of barium sulfate, barium carbonate, zinc oxide, zinc nitride, magnesium oxide, or iron oxide. 
     
     
         17 . The method of  claim 15 , wherein said nano-scale weighting agent comprises a nano-scale-zinc-oxide. 
     
     
         18 . The method of  claim 15 , wherein said gelling agent comprises a multivalent metal ion and at least one ester selected from the group consisting of a phosphoric acid ester and a phosphonic acid ester. 
     
     
         19 . The method of  claim 18 , wherein said multivalent metal ion is at least one selected from the group consisting of a ferric ion, an aluminum ion, a chelated ferric ion and a chelated aluminum ion. 
     
     
         20 . The method of  claim 15 , wherein said rheological additive is an alkyl diamide having a formula: R 1 —HN—CO—(CH 2 ) n —CO—NH—R 2 , wherein n is an integer from 1 to 20, R 1  is an alkyl groups having from 1 to 20 carbons, and R 2  is hydrogen or an alkyl group having from 1 to 20 carbons. 
     
     
         21 . The method of  claim 15 , wherein said rheological additive is present at a concentration of 3-13 pounds per barrel. 
     
     
         22 . The method of  claim 15 , further comprising a solvent for said rheological agent. 
     
     
         23 . The method of  claim 15 , wherein said hydrocarbon fluid comprises at least one selected from diesel, a mixture of diesels and paraffin oil, mineral oil, and isomerized olefins. 
     
     
         24 . The method of  claim 15 , wherein said at least one additive comprises a viscosifying agent. 
     
     
         25 . The method of  claim 15 , wherein said at least one additive comprises a gelling agent. 
     
     
         26 . The method of  claim 15 , wherein said at least one additive comprises a gelling agent and a rheological agent. 
     
     
         27 . The method of  claim 15 , wherein said at least one additive comprises a gelling agent, a rheological agent and a solvent for said rheological agent. 
     
     
         28 . The method of  claim 15  further comprising the step of subsequently recovering some of said viscosified miscible enhanced oil recovery fluid back to the surface from said subterranean petroliferous formation. 
     
     
         29 . The method of  claim 15  further comprising the step of subsequently recovering some of said viscosified miscible enhanced oil recovery fluid by (a) applying a viscosity breaker proximate said viscosified miscible enhanced oil recovery fluid in said subterranean petroliferous formation and (b) flowing said viscosity-broken fluid back to the surface. 
     
     
         30 . The method of  claim 15  further comprising the initial step of determining whether alkalinity conditions exist in said petroliferous formation that could be damaging to said viscosified miscible enhanced oil recovery fluid, and if so, prior to the injection of said miscible viscosified enhanced oil recovery fluid, injecting a mild acid or acid gas to neutralize said alkalinity.