Boosting Low-Carbon Emissions Reduction and Improving Oil Recovery - A Case Study of Gas Injection in Bohai Light Oil Reservoir

Abstract

Abstract Gas-capped oil reservoirs make up a significant proportion of reserves in Bohai basin, thus the efficient development is crucial. Traditional strategy is to deplete the reservoir before water flooding, leveraging the elastic energy. However, under the context of net-zero carbon emissions, flare combustion is no longer suitable. How to effectively handle the associated gas has become a critical challenge for companies, and this is the main concern of this article. Bohai Oilfield has found a collaborative development mode of water and gas injection to better utilize associated gas resources from gas-capped oil reservoirs, which has achieved good results in practice. Firstly, a long core displacement experiment was conducted to explore the synergistic effect of injecting associated gas and water on improving oil recovery, and to clarify the impact of this synergy on the distribution of remaining oil. Secondly, reservoir numerical simulation technology was used to establish a typical model, set different injection modes, and ultimately obtained an alternating injection strategy for injection wells, which helps to improve development strategies.The long core displacement experiment shows that gas injection has significant effects on increasing the dissolved gas-oil ratio, volume coefficient, and reducing viscosity and density for light oil reservoirs. Single injection of gas or water cannot achieve good vertical displacement due to the gravity segregation effect. Therefore, the coordinated development of gas and water injection can maximize the remaining oil and improve recovery. Through numerical simulation, the optimal number of gas and water injection segments was obtained to mitigate the adverse effects of gas invasion and water breakthrough. The design of the first gas injection well in Bohai was guided, and the reinjection gas volume has reached 5.8 billion cubic feet, increasing recovery by 2%. The successful pilot of water-gas synergy development in Bohai Bay indicates a new balance has been achieved in improving recovery, reducing costs, increasing efficiency, and achieving low-carbon development of gas-capped oil reservoirs. This has important reference significance for the offshore oil and gas industry.