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New Approaches to Enhanced Oil Recovery Techniques in Various Categories of Hard-to-recover Reserves in Carbonate Reservoirs

Abstract

Three types of hard-to-recover remaining reserves have been identified. Justification of the most effective regulation technologies has been carried out for each of the reserves group. Reservoir pressure dynamics analysis, differential analysis of remaining reserves structure, laboratory research, geological and mathematical modelling were performed. Advanced technological solutions on carbonate reservoirs were justified. Properties’ specificity of reef reservoirs allows realization of combined technology of creation of underground gas storage with simultaneous production of remaining reserves. Mixed porous-cavern reservoir type determines high heterogeneity what increases probability of gas break-through in the highly permeable reservoir zones. To reduce gas break-through into producing wells and increase sweep by gas influence it is recommended to use gel-forming compositions on the alumo-chloride base. It is suggested using natural demulsifying agent. Effectiveness of flooding in viscous oil and of gas technologies in fractured reservoirs can be increased by emulsion use. Presented are results of study of filtration, rheological characteristics of emulsion based on inverse low-viscosity, low-tar oil. Research on oil-water emulsion on natural emulsifying agent base reveals that oil can be used to prepare reverse emulsions for application as dumping liquid and for water isolation. Hydrophobic reverse emulsions can be used for oil displacement profile levelling in fractured reservoirs and for selective gas and water isolation in producing wells. Compositions, mathematical model and graphical-analytical solution of emulsion stimulation were constructed. Use of heat carrier in fractured-porous field development causes necessity in investigation of high temperatures mechanism extraction. Process investigation allows to offer intensification factors as new reagents and physical principles for strengthening basic thermal development technologies as oil displacement by hot water, steam. With temperature rise displacement intensifies leading to counter-flow thermo-capillary oil displacement. Counter-flow thermo-capillary imbibition of high-viscosity oil is an important displacement factor from porous blocks in the fractured and porous carbonate reservoirs. Mathematical model and calculation methods of steam and gas cyclical impact in fractured reservoirs were developed. All described EOR techniques in fractured carbonate reservoirs have been successfully applied.