Dispersion Polymerization of Microgel in Aqueous Solution of Ammonium Sulfate and its Oil Displacement Efficiency Study

Abstract

Microgel can be used as a novel deep profile control (conformance control) agent in the aspect of EOR(Enhanced oil recovery) in mature oil field development. Dispersion polymerization of microgel has been successfully carried out in aqueous AS (ammonium sulfate) media by using AM (acrylamide), PEG 200 DA (Poly(ethylene glycol(200) diacrylate)), PVP (Poly(vinyl pyrrolidone)), V-50(2,2’-azobis(2-amidino-propane) dihydrochloride), as the monomer, cross-linker, stabilizer and initiator, respectively. The effect of ammonium sulfate and Poly(vinyl pyrrolidone) concentrations are strongly on microgels successfully polymerization. POM（polarization microscope） and SEM （scanning electron microscope）results show that the shape of microgels is in oval or nonspherical state. The surface structure of microgel is rather accidented full of mesoporous. Addition of inorganic salts interacting with poly(acrylamide) microgel can affect its micromorphology and results in the appearance of single crystal clusters. Sand pack flowing experiment shows that the microgel has perfect propagating property during the process of injection and can achieve a high oil recovery efficiency of 23.4% by the total of 0.4 PV microgel solution injection.

Swelling Mechanism Investigation of Microgel with Double-Cross-Linking Structures

“…It is expected to form bulk gel to improve the water shutoff performance by the addition of cross-linkers, such as formaldehyde, methenamine, or phenolic or chromic salt, when injecting microgel. (3) The AFM analysis shows that the swelled microgel has a loose but integral structure, which seems like a "mushroom cloud", indicating the characteristic of the loosening efficacy of the labile cross-linker. The internal structure of the microgel exhibits skeleton structures with chains that are in a state of free stretching.…”

“…1,2 Conformance control is a technique to block the already well-swept layers of reservoir for mobilizing pockets of unswept oil/gas. 3 Cross-linkers, such as chromium(III) salt, 4−6 phenol formaldehyde, 7−9 polyethylenimine (PEI), 10−12 etc., cross-linking with acrylamide-based copolymer or hydrolyzed polyacryamide (HPAM) can form a polymer gel in subterranean formation during a few hours to several days.…”

“…As a chemical method of enhanced oil recovery (EOR), injecting a polymer solution together with a cross-linker proposed for conformance control application has been widely used in mature oilfield development. , Conformance control is a technique to block the already well-swept layers of reservoir for mobilizing pockets of unswept oil/gas . Cross-linkers, such as chromium­(III) salt, − phenol formaldehyde, − polyethylenimine (PEI), − etc., cross-linking with acrylamide-based copolymer or hydrolyzed polyacryamide (HPAM) can form a polymer gel in subterranean formation during a few hours to several days.…”

Water Control with Gels Based on Synthetic Polymers under Extreme Conditions in Oil Wells

“…Microgels are made up of anionic or cationic polymers. PAM microgel prepared by dispersion polymerization in aqueous solution of ammonium sulfate and stabilized with poly(vinylpyrrolidone) results in oval or non‐spherical microgels, which is a rather different shape from the one displayed by microgels polymerized in organic solvents by emulsion polymerization or other polymerization methods 69.…”

“…Microgels are made up of anionic or cationic polymers. PAM microgel prepared by dispersion polymerization in aqueous solution of ammonium sulfate and stabilized with poly(vinylpyrrolidone) results in oval or non-spherical microgels, which is a rather different shape from the one displayed by microgels polymerized in organic solvents by emulsion polymerization or other polymerization methods [69]. Different monomers/comonomers have been used to prepare microgels like N-isopropylacrylamide, methylmethacrylate, methacrylic acid, styrene, divinylbenzene, acrylic acid, N,N'-methylene bisacrylamide, and ethylene glycol dimethacrylate [70].…”