Evaluation Of The Effect Of CO ₂ Flooding On The Black 79 Block In Jilin Oilfield

After years of waterflooding in Hei79block reservoir of jilin, water cut had been rising fast and the development situation had the trend to become poor.In order to improve recovery efficiency and the undeveloped reserves in Hei79block, especially the effective use of rate in low permeability reserves, it had carried out some of the CO2injection flooding field pilot test.But the systematic research on the effectiveness evaluation of CO2injection displacement is rare, as a result, aiming at the production characteristics in Hei79block, indoor experimental evaluation method, numerical simulation method and reservoir engineering theory are combined to conduct an in-depth study on the phase behavior characteristics, miscible characteristics, laboratory evaluation on the oil displacement efficiency of CO2injection and evaluation on the field development effect in the progress of CO2injection displacement in Hei79block.(1)The phase compatibility experiments and phase behavior simulation between CO2and crude oil has been made.Injecting CO2to oil can make oil volume increases about1.54times, viscosity greatly reduced about2times, and significantly improve the liquidity of crude oil. By gas injection P-X phase diagramand pseudo ternary phase diagram calculation, we can draw a conclusionthat, at the present formation pressure, CO2and Hei79block reservoir’s oil cannot reach a contact, but could achieve the effect of evaporation miscible by multiple contact.(2)CO2displacement characteristics of miscible experiments and simulation study have been madeThe initial formation pressure of Hei79block is greater than the minimum miscibility pressure (MMP) which is tested by the tubule experiments, so if we make the formation pressure greater than the minimum miscibility pressure by injecting gas, The reservoir can achieve CO2injection miscible flooding andincrease the oil displacement effect.One-dimensional tube numerical simulation shows that the miscible flooding transition zone properties significantly affected by injection volume and injection pressure. When injection volume must be, the higher injection pressure, the greater the shorter miscible flooding transition zone, the better the oil displacement efficiency; When keep pressure constant, with the increase of gas injection, the transition zone becomes longer, the better the oil displacement efficiency.(3)The indoor evaluation studies about the effect on CO2-oil displacing has been carried outThrough the long core experiments, the continuous CO2flooding experiment and water-gas alternation drive experiment have been made in turn after water flooding and making the pressure some as the original formation pressure.The experimental results show that the ultimate recovery of water-gas alternation drive experiment is smaller than the continuous CO2flooding experiment, but it can effectively solve the problem of poor condition of water flooding development.(4)Promoting the method for evaluating the CO2flooding development effectiveness of oil field.The available maximum recovery has been predicted in Hei79block, Using the equivalent gas rate and recovery degree plate in the process of CO2flooding.The results shows that, the efficiency of CO2flooding can Reached the average level of other oil fields both at home and abroad. Through the establishment of production decline analysis model for gas flooding, drawing a conclusion that it accods with the C decline type for gas flooding in Hei79block.