Complex matrix treatment technologies selection and adaptation for the injection wells of the Republic of Tatarstan oilfields

Nowadays, oil fields on the territory of the Republic of Tatarstan are developed with application of systems for reservoir pressure maintenance, involving injection of large volumes of water into the formation. Efficiency of waterflooding depends on the quality of the injected agent, and, despite the use of various technologies of preparation and treatment of injected water, with the lapse of time critical matrix porosity and permeability inevitably decreases. In this work the main sources of injection wells critical matrix clogging are considered: mechanical impurities, oil products and scales formation, and the results of the component composition analysis of deposits from cluster pumping stations are given. Using the Oddo-Thomson methodology, it is revealed that injected water is prone to calcite and barite deposition at bottomhole conditions. Physicochemical and core-flooding study of several reagents for removing colmatants: acid compositions, hydrocarbon solvents and complexing agents were carried out and their optimal formulations were determined. The matrix treatment technology, including the sequential injection of compositions based on hydrochloric and mud acids, was substantiated. An algorithm for calculating the optimal reagent volume has been developed on the basis of research data on the mineralogical composition of mechanical impurities and ionic composition of injected water. Four types of matrix treatment technologies were determined for the conditions of injection wells at the Romashkinskoye oil field Devonian formation, taking into account the composition of colmatant, and acid treatment designs were developed.