Method to control the physical interface between two or more fluids

Abstract

A method of controlling the physical interface between two wellbore servicing fluids during the displacement of one wellbore servicing fluid by another, the method comprising selecting a liquid plug having a viscosity greater than the viscosity of the two wellbore servicing fluids, introducing a first wellbore servicing fluid into the wellbore, introducing a volume of the liquid plug into the wellbore, and introducing a second wellbore servicing fluid into the wellbore, wherein the liquid plug is selected such that the mixing between the two wellbore servicing fluids is minimized.

1 . A method of controlling the physical interface between two wellbore servicing fluids during the displacement of one wellbore servicing fluid by another, the method comprising:
 (a) selecting a liquid plug having a viscosity greater than the viscosity of the two wellbore servicing fluids;   (b) introducing a first wellbore servicing fluid into the wellbore;   (c) introducing a volume of the liquid plug into the wellbore; and   (d) introducing a second wellbore servicing fluid into the wellbore;   wherein the liquid plug is selected such that the mixing between the two wellbore servicing fluids is minimized.   
     
     
         2 . The method of  claim 1  wherein the liquid plug is capable of being pumped as a plug of viscous material throughout the displacement. 
     
     
         3 . The method of  claim 1  wherein the liquid plug is a thermally activated gellable material that is capable of being pumped in a plug flow condition in a deviated well. 
     
     
         4 . The method of  claim 1  wherein the liquid plug has a diffusion coefficient of from about 1×10 −8  cm 2 /sec to about 1×10 −9  cm 2 /sec as determined by Fick's law of diffusion. 
     
     
         5 . The method of  claim 1  wherein the liquid plug comprises a thermally activated cement and an organophilic product. 
     
     
         6 . The method of  claim 5  wherein the thermally activated cement comprises magnesium oxide and the organophilic product comprises alkyl quaternary ammonium montmorillonite. 
     
     
         7 . The method of  claim 1  wherein the liquid plug is selected from the group consisting of non-linear elastic solids, viscoelastics, non-linear viscous fluids or combinations thereof. 
     
     
         8 . The method of  claim 1  wherein the liquid plug has a shear viscosity of from about 100 cp to about 2,000,000 cp. 
     
     
         9 . The method of  claim 1  wherein the liquid plug has a yield stress of from about 40 Pascals to about 40,000 Pascals. 
     
     
         10 . The method of  claim 1  wherein the liquid plug has an elasticity of from about 0.005 psi to about 10,000 psi. 
     
     
         11 . The method of  claim 1  wherein the liquid plug has a plasticity of from about 0.005 psi to about 10,000 psi. 
     
     
         12 . The method of  claim 1  wherein the liquid plug has a shear stress history response of from about 1000 to about 10 million. 
     
     
         13 . The method of  claim 1  wherein the liquid plug is used as a surface pressure indicator. 
     
     
         14 . The method of  claim 1  wherein the liquid plug comprises a crosslinkable polymer system and a filler,
 wherein the crosslinkable polymer system comprises a water soluble copolymer of a non-acidic ethylenically unsaturated polar monomer and a copolymerizable ethylenically unsaturated ester; a water soluble terpolymer or tetrapolymer of an ethylenically unsaturated polar monomer, an ethylenically unsaturated ester, and a monomer selected from acrylamide-2-methylpropane sulfonic acid, N-vinylpyrrolidone, or both; or combinations thereof; and a crosslinking agent comprising a polyalkyleneimine, a polyfunctional aliphatic amine, an aralkylamine, a heteroaralkylamine, or combinations thereof.   
     
     
         15 . The method of  claim 1  wherein selecting the liquid plug comprises trial and error, computational modeling, or a combination thereof. 
     
     
         16 . The method of  claim 15 , wherein the computational modeling comprises inputting the fluid properties of the two well servicing fluids, including density, rheology, chemical composition, and diffusion coefficients; wellbore geometry, including deviation, casing geometry and placement, pumping schedule including rates and volumes; and pressure, temperature, fluid compressibility, formation properties; and calculating the degree of intermixing of the two well servicing fluids. 
     
     
         17 . The method of  claim 14  wherein the crosslinkable polymer system comprises a copolymer of acrylamide and t-butyl acrylate and the crosslinking agent comprises polyethylene imine. 
     
     
         18 . The method of  claim 1  wherein the liquid plug comprises a crosslinkable polymer system that is thermally activated. 
     
     
         19 . The method of  claim 18  wherein the thermal activation occurs from about 180° F. to about 320° F. 
     
     
         20 . The method of  claim 14  wherein the filler comprises alkyl quaternary ammonium montmorillonite, bentonite, zeolites, barite, fly ash, calcium sulfate, or combinations thereof. 
     
     
         21 . The method of  claim 14  wherein the filler comprises a hydratable polymer, an organophilic clay, a water-swellable clay, or combinations thereof. 
     
     
         22 . The method of  claim 14  wherein the filler comprises alkyl quaternary ammonium montmorillonite. 
     
     
         23 . The method of  claim 1  wherein the liquid plug comprises a packing agent. 
     
     
         24 . The method of  claim 23  wherein the packing agent is a resin coated particulate. 
     
     
         25 . A method of placing a settable spacer in a wellbore in a subterranean formation comprising:
 (a) selecting a liquid plug composition comprising a thermally activated cement and an organophilic product and having a viscosity,   wherein the viscosity of the liquid plug is chosen such that intermixing of the liquid plug with the wellbore servicing fluids ahead of and behind it is minimized;   (b) pumping a volume of the liquid plug into the wellbore;   (c) stopping circulation of the wellbore fluids when a surface pressure spike is indicated; and   (d) allowing the cement to set.   
     
     
         26 . A method of separating servicing fluids during a wellbore service operation comprising: placing a liquid plug between the interface of two dissimilar wellbore servicing fluids, wherein the liquid plug is rheologically designed to minimize the mixing between the interfaces of the liquid plug and the wellbore servicing fluids.