Characteristics Of Co - Mixing Of CO ₂ In Herbage Et Reservoir And Its Effect Evaluation Method

At present, the technology of CO2flooding has been very mature in foreign countries. In order to further develop the remaining and potential land reservoir, our countries has carried out some CO2flooding pilot tests in Jilin, Daqing, Shengli, Zhongyuan, Jiangsu oil field, and has achieved initial success so far. However, because our country is still in its infancy in terms of recovery by CO2injection, related research is not much, so the investigation of the miscible characteristics and effects between oil and CO2becomes so important, and it has a guiding significance for the reservoir’s further development.In the terms of Taizhou group’s production characteristics at present, this paper made a concrete analysis for the reservoir characteristics of miscible by using indoor experiment evaluation method, single well numerical simulation and reservoir engineering theory. Combined with the field production datas, the calibration chart for predicting the biggest increased recovery after injecting CO2has been established.The main conclusion is as follows:1) The phase compatibility experiments and phase behavior simulation between CO2and crude oil has been made.Injecting CO2to oil can make oil volume increases, viscosity greatly reduced, and significantly improve the liquidity of crude oil. By gas injection P-X phase diagram and pseudo ternary phase diagram calculation, we think that, at the present formation pressure, CO2and Taizhou group reservoir’s oil cannot reach a contact, but could achieve the effect of evaporation miscible by multiple contact forward.2) CO2displacement characteristics of miscible experiments under the condition of two different porous medias.The present formation pressure of Taizhou group is greater than the minimum miscibility pressure (MMP) which is tested by the tubule experiments, so that CO2injection miscible flooding can be implemented successfully in this reservoir. By real long core experiment, we found that when the injection pressure is higher than the MMP, the recovery efficiency is usually high, and gas breakthrough later.3) Using one-dimensional tubule and injection-production well group profile miscible flooding numerical simulation study the nature of the transition zone and the miscible mechanism.One-dimensional tube profile and two-dimensional injection-production well group profile 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 smaller the viscosity, the better the displacement effect; When keep pressure constant, with the increase of gas injection, the transition zone becomes longer, the affected range of CO2from gas injector is wide.4) The CO2miscible flooding chart of equivalent gas rate and recovery degree has been established.In terms of water drive characteristic curves and improved tong’s chart, the CO2miscible flooding equivalent gas rate and recovery degree chart is established. Using the chart to predict Taizhou group reservoir’s rasied maximum recovery after CO2injection, and compared with that of other oil field at home and abroad, the result compared with Taizhou group reservoir’s actual situation.