Enhanced oil recovery polymers

Influence of Calcium on Adsorption Properties of Enhanced Oil Recovery Polymers... 

The most widely used synthetic and natural enhanced oil recovery polymers, such as partially hydrolyzed polyacrylamide, carboxymethyl(ethyl) cellulose, polysaccharides, or xanthan gums, are not suitable for high-temperature reservoirs (> 90 °C) with high-density brine fluid due to excessive hydrolysis and precipitation [277]. The main advantages of polymeric betaines over the mentioned standard polymers are (1) thermostability (up to 120 °C) (2) brine compatibility and (3) viscosification in brine solution [278]. Carbobetaines grafted onto hydroxyethyl cellulose were tested as a drilling-mud additive for clay hydration inhibition and mud rheological control [279]. An increase in the content of carbobetaine moieties resulted in an enhanced inhibitive abiUty, especially for sahne mud. 

Steady shear flow measnrements, however, can measure only viscosity and the first normal stress difference, and it is difficult to derive information abont fluid structure from such measurements. Instead, dynamic oscillatory rheological measurements are nsed to characterize both enhanced oil recovery polymer solutions and polymer crosslinker gel systems (Prud Homme et al., 1983 Knoll and Pmd Homme, 1987). Dynamic oscillatory measurements differ from steady shear viscosity measnrements in that a sinusoidal movement is imposed on the fluid system rather than a continnons, nnidirectional movement. In other words, the following displacement is imposed ... 

For reviews, see articles presented in symposium entitled Polymers in Enhanced Oil Recovery, Polym. Prepr., 22(2),... 

Microemulsions became well known from about 1975 to 1980 because of their use ia "micellar-polymer" enhanced oil recovery (EOR) (35). This technology exploits the ultralow iaterfacial tensions that exist among top, microemulsion, and bottom phases to remove large amounts of petroleum from porous rocks, that would be unrecoverable by conventional technologies (36,37). Siace about 1990, iaterest ia the use of this property of microemulsions has shifted to the recovery of chloriaated compounds and other iadustrial solveats from shallow aquifers. The latter appHcatioa (15) is sometimes called surfactant-enhanced aquifer remediation (SEAR). 

Micellar/polymer (MP) chemical enhanced oil recovery systems have demonstrated the greatest potential of all of the recovery systems under study (170) and equivalent oil recovery for mahogany and first-intent petroleum sulfonates has been shown (171). Many somewhat different sulfonate, ie, slug, formulations, slug sizes (pore volumes), and recovery design systems were employed. Most of these field tests were deemed technically successful, but uneconomical based on prevailing oil market prices (172,173). 

Polymers and Supercritical Fluids. Prior to the mid-1980s, Httie information was pubhshed regarding polymer processing with supercritical and near-critical fluids (1). In 1985, the solubiUties of many polymers in near- and supercritical CO2 were reported. These polymers were examined for thek abiUty to increase viscosity in C02-enhanced oil recovery (24). Since then, a number of studies have examined solubiUties of polymers in... 

Acrylamide—polymer/Ct(III)catboxylate gel technology has been developed and field tested in Wyoming s Big Horn Basin (211,212). These gels economically enhance oil recovery from wells that suffer fracture conformance problems. The Cr(III) gel technology was successful in both sandstone and carbonate formations, and was insensitive to H2S, high saline, and hard waters (212). 

A clear solution of aluminum citrate neutralized to pH 7 is used for in situ gelling of polymers in polymer flooding and well stimulation in enhanced oil recovery techniques (128—132). The citrate chelate maintains aluminum ion solubiUty and controls the rate of release of the aluminum cross-linker. 

Among the basic fields of applications, the major use of acrylamide polymers is liquid-solid separation in water treatment and waste treatment. Smaller quantities are used in the manufacturing of paper and in the processing of minerals in mining. Relatively nonlarge quantities are use as additives for enhanced oil recovery. 

Pseudozan is an exopolysacchaiide produced by a Pseudomonas species. It has high viscosities at low concentrations in formation brines, forms stable solutions over a wide pH range, and is relatively stable at temperatures up to 65° C. The polymer is not shear degradable and has pseudoplastic behavior. The polymer has been proposed for enhanced oil-recovery processes for mobility control [1075]. 

The oil production from thin under-gas cap zones with an active aquifer is not efficient because of the rapid breakthrough of gas or water. The water-alternating gas technology based on the injection of water solution with oil-and water-soluble polymers seems to be promising to stimulate such wells. For heavy oils, this technology can be considered as an alternative to thermal-enhanced oil recovery [1673]. 

A chemical-enhanced oil-recovery technology can be used to remove oily contaminants from soil. Laboratory studies demonstrated that a variety of alkaline-surfactant combinations can be used with a polymer to reduce the residual oil saturation in waterflooding [1435]. 

S. Bailey, R. Bryant, and T. Zhu. A microbial trigger for gelled polymers. In Proceerfingi Volume, pages 611-619.5th US DOE et al Microbial Enhanced Oil Recovery Relat Biotechnol for Solving Environ Probl Int Conf (Dallas, TX, 9/11-9/14), 1995. 

M. R. Islam and A. Chakma. Mathematical modelling of enhanced oil recovery by alkali solutions in the presence of cosurfactant and polymer. / Plefro/ Sci Eng, 5(2) 105-126, February 1991. 

C. L. McCormick and R. D. Hester. Polymers for mobility control in enhanced oil recovery final report. US DOE Fossil Energy Rep DOE/BC/10844-20, Southern Mississippi Univ, 1990. 

W. T. Osterloh and M. J. Jante, Jr. Surfactant-polymer flooding with anionic PO/EO surfactant microemulsions containing polyethylene glycol additives. In Proceedings Volume, volume 1, pages 485 94. 8th SPE/DOE Enhanced Oil Recovery Symp (Tulsa, OK, 4/22-4/24), 1992. 

Residuum oil supercritical extraction (ROSE) (petroleum deasphalting) Polymer and edible oils fractionation CO2 enhanced oil recovery Analytical SCF extraction and chromatography Infusion of materials into polymers (dyes, pharmaceuticals)... 

Oil-field chemistry has undergone major changes since the publication of earlier books on this subject Enhanced oil recovery research has shifted from processes in which surfactants and polymers are the primary promoters of increased oil production to processes in which surfactants are additives to improve the incremental oil recovery provided by steam and miscible gas injection fluids. Improved and more cost-effective cross-linked polymer systems have resulted from a better understanding of chemical cross-links in polysaccharides and of the rheological behavior of cross-linked fluids. The thrust of completion and hydraulic fracturing chemical research has shifted somewhat from systems designed for ever deeper, hotter formations to chemicals, particularly polymers, that exhibit improved cost effectiveness at more moderate reservoir conditions. 

Chemicals of various types are used in every stage of drilling, completing, and producing oil and gas wells. This review describes these chemicals, why they are used, and recent developments. These chemicals include common inorganic salts, transition metal compounds, common organic chemicals and solvents, water-soluble and oil-soluble polymers, and surfactants. As existing fields become depleted, use of chemistry to maintain production via well stimulation, more efficient secondary recovery operations, and enhanced oil recovery become ever more important. 

Recent research and field tests have focused on the use of relatively low concentrations or volumes of chemicals as additives to other oil recovery processes. Of particular interest is the use of surfactants as CO (184) and steam mobility control agents (foam). Also combinations of older EOR processes such as surfactant enhanced alkaline flooding and alkaline-surfactant-polymer flooding have been the subjects of recent interest. Older technologies polymer flooding (185,186) and micellar flooding (187-189) have been the subject of recent reviews. In 1988 84 commercial products polymers, surfactants, and other additives, were listed as being marketed by 19 companies for various enhanced oil recovery applications (190). 

Propagation of enhanced oil recovery chemicals through rock is critical to the success of an EOR project. Polymer retention in permeable media has been the subject of considerable study (349)... 

Huang, C-G. Green, D.W. Willhite, G.P. "An Experimental Study of the In-Situ Gelation of Chromium(+3)-Polyacrylamide Polymer in Porous Media", SPE/DOE paper 12638, 1984 SPE/DOE Fourth Symposium on Enhanced Oil Recovery, Tulsa, April 15-18. 

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