Analysis of the dynamics of pressure and temperature at the bottom of an injection well during injection of water and water-gas mixture

UDK: 622.276.53.054.23:621.67−83

DOI: 10.24887/0028-2448-2025-10-60-64

Key words: simultaneous water and gas (SWAG) injection, pump-ejector system (PES), water-gas mixture, bottomhole pressure and temperature, associated petroleum gas, mineralized water, hydrate formation prevention, enhanced oil recovery, downhole monitoring, foaming agents, annular gas utilization

Authors: V.N. Kalinnikov (Sofoil LLC, RF, Kazan); A.N. Drozdov (RUDN University, RF, Moscow; Gubkin University, RF, Moscow; Sergo Ordzhonikidze Russian State University for Geological Prospecting, RF, Moscow); K.I. Chernishov (Tatneft-Dobycha JV, RF, Almetyevsk); A.M. Galimov (TATNEFT PJSC, RF, Almetyevsk); E.I. Gorelkina (RUDN University, RF, Moscow; Sergo Ordzhonikidze Russian State University for Geological Prospecting, RF, Moscow)

This paper discusses certain aspects of implementing a simultaneous water and gas injection (SWAG) technology at a pilot site within a terrigenous reservoir of the Romashkino oilfield in the Republic of Tatarstan. The injection was carried out using a pump–ejector system (PES). Operating parameters were monitored by wellhead pressure sensors, along with gas and water flowmeters. Fresh water from the reservoir pressure-maintenance system and associated petroleum gas collected from the annular space of 11 producing wells were used as injection agents. The gas was delivered to the ejector mixing chamber through a dedicated gas-gathering system. Three injection wells were selected as recipient wells, one of which operated under a simultaneous–separate injection. The initial pilot tests of SWAG injection revealed a gradual increase in discharge pressure of the booster pump during PES operation, due to a decline in injectivity of the well. To obtain additional downhole data, a high-resolution downhole logging tool was deployed in one of the injection wells. The analysis of the acquired data suggested the formation of gas hydrates and subsequent near-wellbore plugging. To test this hypothesis, associated gas and mineralized water with a density of 1180 kg/m³ were injected. The discharge pressure of the pump remained stable over a two-day period, confirming that hydrate formation can be prevented when mineralized saline water is used. Due to a reduction in annular pressure in one of the gas donor wells, its operating mode changed from intermittent to stable continuous production, thereby demonstrating the efficiency of the PES.

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