Large fields of TATNEFT PJSC, at their current stage of development, are characterized by oil production decline, deterioration of reserves structure and ever-increasing water cut of production wells. This is attributable to depletion of active oil reserves with the resultant increase in the share of residual oil trapped in unswept zones and oil reserves physically or chemically bound to reservoir rock. Complex geological structure of major production intervals, characterized by substantial permeability heterogeneity, results in water flow primarily to high-permeability interlayers, thus leaving low-permeability reservoir zones partially or completely unflushed. Regardless of natural oil production decline in the Republic of Tatarstan, particularly at the Romashkinskoye oil field, TATNEFT has succeeded not only in stabilization of oil production, but also in boosting the current production rates. This was made possible due to application of efficient field development technologies based on contour waterflooding, bringing into active development of hard-to-recover reserves, and large-scale implementation of enhanced oil recovery (EOR) methods. Application of chemical EOR methods aimed to control conformance of injection wells, redistribute fluid flows and reduce water cut of produced fluid is one of the efficient solutions to improve production performance of complex fields, especially at late stages of development. Despite abundance of available methods and chemical compositions, only a few of them proved beneficial in terms of production and economic performance. These are polymer compositions, suspensions, sedimentation and gelling compositions and hydrophobic emulsion systems. Injection of gelling, dispersion, and sedimentation compositions can completely block high- and medium-permeability reservoir intervals that contain considerable residual oil reserves despite high water saturation. This puts such intervals out of operation for a long time to the extent that they become non-producing. In light of the above, development and implementation of EOR technologies allowing for selective, partial or complete, temporary shut-off of water flow to high-permeability flushed zones to redistribute the injected water to low and medium-permeability reservoir zones is of utmost importance.
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