Exploitation Effect Evaluation Of CO₂ Flooding In Low Permeability Reservoir After Waterflooding

The low permeability reservoirs are faced with problems such as high water content,water injection difficulties and low oil recovery rate in the late development of waterflooding.In this paper,the Liaohe Oilfield Huan 26 block Dujiatai reservoir as the target block to carry out research.The target block is a typical low-permeability reservoir,the development time has been more than 30 years,the degree of recovery less than 20%.In order to improve the effect of the development of the Huan 26 block Dujiatai reservoir,it is proposed to carry out CO₂ flooding development.CO₂ flooding is an important means to improve the development of low permeability reservoirs.There is currently lack of a way to evaluate CO₂ flooding comprehensively.In this paper,seven factors influencing the development of CO₂flooding were selected,and the seven-factor Box-Behnken model was designed by using the response surface method.The established model could quickly evaluate the minimum miscible pressure and provide reference for CO₂ flooding evaluation of similar reservoirs.The application of CO₂ flooding in the development of oil and gas fields is an effective way to use greenhouse gases.The material balance method is used to evaluate the CO₂ embedding potential of Huan 26 block.The buried amount of CO₂ is15.756×10⁴ tons and the CO₂ 10.2414×10⁴ tons,Liaohe Oilfield Huan 26 block has a good potential for CO₂ storage.Evaluation of the implementation of CO₂ flooding in Liaohe Oilfield has been carried out from the aspects of crude oil phase simulation and typical reservoir development characteristics.First,a 15-component state equation parameter?EoS-15?was established to simulate the crude oil phase.The minimum miscible pressureis23.75 MPa,which is lower than the average formation pressure at the end of the water flooding.Then,the numerical simulation software is used to simulate the water injection development and the characteristics of CO₂ flooding in typical well groups.The results show that some of the crude oil remaining in the process of water flooding is extracted and the water content of the formation is reduced.The interfacial tension of the gas and oil is less than 0.1 mN/m,indicating that the CO₂ flooding can achieve the miscible flooding in the Huan 26 block.