The key stages of injecting carbon dioxide into oil reservoirs in order to enhance oil recovery and stimulate oil production

Solving the world-class problem of reducing greenhouse gas emissions into the atmosphere and potential utilization of carbon dioxide (CO₂), the article provides an overview of technologies for injecting CO₂ into the oil and gas reservoirs to enhance oil recovery and stimulate oil production. Two main methods of carbon dioxide (CO₂) injection are proposed and described in detail. These are the Huff and Puff method, which involves the injection of CO₂ into production wells, and CO₂ injection into injection wells.
The technology of injecting carbon dioxide into production wells has a number of advantages, such as the lack of capital costs and low operating costs, quick effect manifested in increased oil rates and efficient use of CO₂. The general principle of the technology is the controlled supply of carbon dioxide through the mouth of a shut-in production well into the bottomhole formation zone. The efficiency of the technology is achieved primarily through the reduction of oil viscosity and volumetric expansion of oil, the decrease of interfacial tension, and the reduction of relative phase permeability by water. Consequently, residual oil saturation is reduced by the increase in the amount of trapped gas.
The second technology for injecting carbon dioxide into injection wells to achieve a positive technological effect requires a larger volume of injection agent and a longer period for evaluation of the effect. The efficiency of the technology and the increase in the oil displacement ratio are achieved through the distribution of large volumes of injected carbon dioxide through low-permeability reservoir channels and involvement of residual oil.
The article presents the necessary conditions and main stages of CO₂ injection process organization using the proposed technologies, and describes the composition of the required equipment. Special attention is paid to the necessity of using inhibitors to protect downhole equipment, as well as to the selection of suitable inhibitors, taking into account their physical and chemical characteristics, compatibility with other reagents and reservoir properties. The authors of the article have conducted an expert survey of the market for the availability of specialized equipment in Russia and the services of domestic manufacturers in the field of gas injection technologies.
The conclusion of the article highlights the importance of CO₂ injection careful planning and monitoring, as well as the potential of gas-enhanced methods to improve production and reduce environmental impact.

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