Petroleum recovery process and system

Abstract

A system and process are provided for recovering petroleum from a formation. An oil recovery formulation comprising at least 75 mol % dimethyl sulfide that is first contact miscible with a liquid petroleum composition is introduced into a petroleum bearing formation, an oil immiscible formulation is introduced into the formation subsequent to introduction of the oil recovery formulation into the formation, and petroleum is produced from the formation.

What is claimed is: 
     
         1 . A method for recovering petroleum comprising:
 providing an oil recovery formulation that comprises at least 75 mol % dimethyl sulfide and that is first contact miscible with liquid phase petroleum;   introducing the oil recovery formulation into a petroleum-bearing formation;   contacting the oil recovery formulation with petroleum in the formation;   introducing an oil immiscible formulation into the petroleum-bearing formation subsequent to the introduction of the oil recovery formulation into the formation; and   producing petroleum from the formation after introduction of the oil immiscible formulation into the formation.   
     
     
         2 . The method of  claim 1  wherein the petroleum-bearing formation is a subterranean formation. 
     
     
         3 . The method of  claim 1  wherein the oil recovery formulation is introduced into the formation by injection via a first well extending into the formation, the oil immiscible formulation is introduced into the formation by injection via the first well subsequent to introduction of the oil recovery formulation into the formation, and petroleum is produced from a second well extending into the formation. 
     
     
         4 . The method of  claim 3  wherein from 0.001 to 5 pore volumes of the oil recovery formulation is introduced into the formation and the oil immiscible formulation is in liquid phase and from 0.001 to 5 pore volumes of the oil immiscible formulation is introduced into the formation. 
     
     
         5 . The method of  claim 1  wherein the oil recovery formulation is first contact miscible with petroleum in, or from, the formation. 
     
     
         6 . The method of  claim 1  wherein the oil recovery formulation has a dynamic viscosity of at most 0.35 mPa s (0.3 cP) at 25° C. 
     
     
         7 . The method of  claim 1  wherein the oil recovery formulation is introduced into the formation at a pressure of from 20% to 99% of the fracture pressure of the formation. 
     
     
         8 . The method of  claim 1  wherein the oil immiscible formulation is not first contact miscible or multiple contact miscible with petroleum in the petroleum-bearing formation. 
     
     
         9 . The method of  claim 1  wherein the oil immiscible formulation is selected from the group consisting of an aqueous polymer solution, water in gas or liquid form, carbon dioxide at a pressure below its minimum miscibility pressure with petroleum in the formation, nitrogen at a pressure below its minimum miscibility pressure with petroleum in the formation, air, or mixtures thereof. 
     
     
         10 . The method of  claim 9  wherein the aqueous polymer solution includes a polymer selected from the group consisting of polyacrylamides, partially hydrolyzed polyacrylamides, polyacrylates, co-polymers of acrylic acid and acrylamide, co-polymers of acrylic acid and lauryl acrylate, co-polymers of lauryl acrylate and acrylamide, xanthan gum, guar gum, alginic acids, alginate salts, carboxymethylcellulose, polyvinyl alcohols, polystyrene sulfonates, polyvinylpyrrolidones, 2-acrylamide-2-methyl propane sulfonate, and combinations thereof. 
     
     
         11 . The method of  claim 1  wherein the oil immiscible formulation is introduced into the formation at a pressure of from 20% to 99% of the fracture pressure of the formation. 
     
     
         12 . The method of  claim 1  wherein the oil immiscible formulation is in gaseous phase and the oil recovery formulation is in liquid phase, and the oil immiscible formulation is introduced into the formation at a volume ratio relative to the oil recovery formulation introduced into the formation of at least 20:1. 
     
     
         13 . The method of  claim 1  wherein the oil immiscible formulation is in liquid phase, and the oil immiscible formulation is introduced into the formation at a volume ratio relative to the oil recovery formulation of from 0.1:1 to 10:1. 
     
     
         14 . The method of  claim 1  wherein the oil immiscible formulation has a dynamic viscosity of at least one order of magnitude greater than a mixture of the oil recovery formulation and petroleum from the formation. 
     
     
         15 . A system, comprising:
 an oil recovery formulation comprised of at least 75 mol % dimethyl sulfide that is first contact miscible with liquid phase petroleum;   an oil immiscible formulation selected from the group consisting of an aqueous polymer solution, water in gas or liquid form, carbon dioxide at a pressure below its minimum miscibility pressure with petroleum in the formation, nitrogen at a pressure below its minimum miscibility pressure with petroleum in the formation, air, and mixtures thereof;   a petroleum-bearing formation;   a mechanism for introducing the oil recovery formulation into the petroleum-bearing formation;   a mechanism for introducing the oil immiscible formulation into the petroleum-bearing formation subsequent to introduction of the oil recovery formulation into the formation; and   a mechanism for producing petroleum from the petroleum-bearing formation subsequent to the introduction of the oil immiscible formulation into the formation.   
     
     
         16 . The system of  claim 15  wherein the petroleum-bearing formation is a subterranean formation. 
     
     
         17 . The system of  claim 15  wherein the oil recovery formulation is first contact miscible with petroleum in, or from, the petroleum-bearing formation. 
     
     
         18 . The system of  claim 15  wherein the oil immiscible formulation is immiscible with petroleum in, or from, the petroleum-bearing formation. 
     
     
         19 . The system of  claim 15  wherein the mechanism for introducing the oil recovery formulation into the petroleum-bearing formation is located at a first well extending into the formation. 
     
     
         20 . The system of  claim 19  wherein the mechanism for introducing the oil immiscible formulation into the petroleum-bearing formation is located at the first well. 
     
     
         21 . The system of  claim 20  wherein the mechanism for producing petroleum from the petroleum-bearing formation is located at the second well extending into the formation.