The main producing formations of Central-Khoreiver uplift fields are carbonate Devonian deposits (Famenian stage) that are characterized by mixed-wet surface, reservoir temperatures around 70°C and high salinity formation water – up to 210 g/l. A study is currently in progress these object to evaluate the injection of different chemical agents to increase oil recovery factor. The paper includes the scheme of surfactant and surfactant-polymer composition selection and the approach to evaluate potential results of injection of the most prospective composition. Application of surfactant compositions was evaluated for high salinity treated formation water (without applying salinity gradient). The first step of surfactant composition selection included testing of water solution stability in formation water with salinity that is characteristic for Central-Khoreiver uplift conditions. Then interfacial tension of surfactant water solution with oil was measured, as well as adsorption properties. Surfactant water solutions cannot reach the conditions to form Winsor type (III) microemulsions with oil at that high salinity. The target values of interfacial tension were set in the range around 10-2, and not higher than 10-1 mN/m. Three most promising surfactant compositions were selected from the results of physical-chemical experiments, with acceptable IFT and static adsorption properties. Filtration experiments on composite core model were conducted to evaluate the efficiency of selected composition. The maximum obtained level of incremental oil recovery from the porous medium in comparison with water injection was 22%; surfactant recommended for additional experimental program. On the next stage, polymers were selected, dynamic adsorption of surfactant and polymers was measured on water-saturated core and mixed surfactant-polymer composition properties were evaluated. Low interfacial tension confirmed on the interface of surfactant-polymer composition with oil and there was no negative influence of surfactant on polymer viscosity. Obtained parameters were used to build a sector model of field development unit. Technological efficiency is high for the selected scheme of composition injection in the considered conditions.
References
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