Reservoir treatments

Abstract

The present invention relates to the field of enhanced oil recovery and provides a method of establishing a plug in a hydrocarbon reservoir, the method comprising introducing into the reservoir a formulation comprising solid particles and a viscosifier and then reducing the viscosity of said viscosifier, thereby causing said solid particles to form a plug within said hydrocarbon reservoir. Also provided is a method of establishing a plug in a hydrocarbon reservoir, the method comprising introducing into the reservoir a formulation comprising: (a) microorganisms or cell-free enzymes; (b) solid particles; and (c) a viscosifier which is a substrate for the microorganisms or cell-free enzymes of (a). Also provided is a formulation comprising: (a) microorganisms or cell-free enzymes; (b) solid particles made from wood or a wood derived product; and (c) a viscosifier which is a substrate for the microorganisms or cell-free enzymes of (a).

1 - 21 . (canceled) 
     
     
         22 . A formulation comprising:
 (a) microorganisms or cell-free enzymes;   (b) solid particles; and   (c) a viscosifier which is a substrate for the microorganisms or cell-free enzymes of (a);   wherein the solid particles (i) are substantially spherical, and (ii) have a core which is not deformable and an outer layer which is deformable.   
     
     
         23 . The formulation of  claim 22 , further comprising growth medium. 
     
     
         24 . The formulation of  claim 22 , wherein the microorganisms or cell-free enzymes are saccharolytic or lignocellulolytic. 
     
     
         25 . The formulation as claimed in  claim 22 , wherein the microorganisms are, or wherein the cell-free enzymes are from,  Clostridium thermocellum  or  Acidothermus cellulolyticus.    
     
     
         26 . The formulation of  claim 22 , wherein the viscosifier comprises, cellulose, hemicellulose or a derivative thereof or a polysaccharide gum. 
     
     
         27 . The formulation of  claim 26 , wherein the viscosifier comprises a polyanionic cellulose or a microfibrillated cellulose. 
     
     
         28 . The formulation of  claim 27 , wherein the viscosifier comprises carboxymethyl cellulose. 
     
     
         29 . The formulation of  claim 22 , wherein the solid particles have the same density as the rest of the formulation. 
     
     
         30 . The formulation of  claim 22 , wherein the solid particles are substantially uniform in size. 
     
     
         31 . The formulation of  claim 22 , wherein the formulation is made up of 25-70% by volume of the solid particles. 
     
     
         32 . The formulation of  claim 22 , wherein the solid particles of the formulation comprise a first population of solid particles and a second population of solid particles, wherein said first population are at least five times larger than said second population. 
     
     
         33 . The formulation of  claim 22 , wherein the solid particles of the formulation comprise a population of solid particles which are 0.05 to 5 mm in diameter. 
     
     
         34 . The formulation of  claim 22 , wherein the solid particles of the formulation comprise a population of solid particles which are <0.2 mm but ≥1 μm in diameter. 
     
     
         35 . The formulation as claimed in  claim 22 , wherein the solid particles of the formulation comprise a population of solid particles which are 1 to 100 μm in diameter. 
     
     
         36 . The formulation of  claim 22 , wherein the formulation comprises a colloid comprising a continuous phase and a dispersed phase in which the solid particles are the dispersed phase. 
     
     
         37 . The formulation of  claim 22 , wherein the formulation is an aqueous formulation. 
     
     
         38 . The formulation of  claim 22 , wherein the formulation has a viscosity of 5-15 cPa. 
     
     
         39 . The formulation of  claim 22 , wherein the particles are made from wood or a wood derived product.