Analysis And Research On The Influencing Factors Of CO₂ Flooding In Low Permeability Multi-layer Reservoir

Carbon dioxide(CO2)is a greenhouse gas and an important factor for global warming.Therefore,the reduction of CO2 emissions is a problem that needs to be solved urgently.The petroleum industry has used CO2 as a resource to displace oil and provide oil recovery,which is an important measure to protect the environment and reduce greenhouse gases,therefore,the study of the application of carbon dioxide in the flooding of block Mao-3 in Huabei oilfields very significant.This paper takes the block Mao-3 in Huabei oilfield as an example,according to the reservoir geological characteristics and reservoir fluid characteristics of this block,CO2 flooding mechanism,calculation method of miscible pressure were researched,and by using the numerical simulation method,the production dynamics of carbon dioxide flooding were simulated,and the influencing factors of dioxide flooding were analyzed and the influences of different operating parameters on the flooding effect were calculated.The research in this paper has achieved the following results:(1)the volume effect of CO2 flooding was clarified,the influence of phase behavior to the flooding effect and the adaptability of CO2 flooding technology were analyzed,as a result the evaluation method of CO2 flooding effect was obtained;(2)the calculation method of miscible pressure of CO2 flooding was researched,and two different calculation methods of miscible pressure(MMP)were analyzed:empirical formula and numerical simulation of slim-tube experiment by using the Eclipse-Schlumberger 300,the actual fluid data of Mao 3 reservoir in Huabei oilfield were used for calculation.The results show that the minimum miscible pressure of carbon dioxide in Mao 3 reservoir is 31Mpa;(3)taking the actual data of the Mao 3 oil layer as an example,the compositional reservoir simulation of CO2 flooding calculation was established,and the factors that affect CO2 flooding efficiency are obtained to increase the oil recovery of the Mao 3reservoir;(4)through the numerical simulation method,the production dynamic characteristics of CO2 flooding were obtained,the research results show that continuously injecting CO2,the oil recovery improvement was about 6-10%.Thehighest oil recovery was about 22%,continuously injecting 24000 m3/day gas extremely improves the EOR.In the case of WAG,the oil recovery was about 39-43%.In this study the different WAG ratio was done with 2 scenarios that were 1: 2and 2: 1.The study shows the oil recovery performance for different water and gas ratio of injection that WAG with 2:1 is better than 1:2.By injecting water for 4 years following by 2 years of gas could recover about 45% oil recovery;...