低渗透油藏中CO₂与原油的相互作用*

Interaction between CO₂ and Crude Oil in Low Permeability Reservoir

刘家军 李立峰 高 苗

LIU Jiajun LI Lifeng GAO Miao

为更好地指导CO2驱在低渗透油藏的应用，研究了CO2与原油相互作用及其对CO2吞吐采油效果的影响。 首先从溶解和萃取两个方面分析了不同压力下CO2-原油的相互作用规律；然后利用设计的岩心模型开展了CO2 吞吐采油实验，同时对驱替前后的岩心进行了核磁共振扫描，明确剩余油分布状态；最后结合江苏油田应用实 例，提出下一步CO2采油技术应用方向。结果表明，压力超过萃取开始压力（10.0 MPa）时，萃取率随压力的升高 显著增大，40.0 MPa时的萃取率为85.2%。压力小于原油收缩压力（13.0 MPa）时，原油表现为体积膨胀，最大膨 胀系数1.25；压力大于13.0 MPa时，在CO2对原油的强萃取作用下，原油体积明显收缩。吞吐实验结果表明，对 于长度为6.0 cm的低渗基质岩心，CO2可采出48.0%的原油，初期主要增产机理为CO2在原油中溶解膨胀，后期主 要增产机理为CO2萃取原油中的轻质组分。在实际应用中，需充分考虑油藏条件对CO2与原油作用的影响，压力 低于15 MPa的油藏应优先考虑CO2吞吐，高于15 MPa的油藏应优先考虑CO2驱。图8参16

In order to improve the efficiency of CO2 flooding in low permeability reservoir，the interaction between CO2 and crude oil and the influence on CO2 flooding were studied. Firstly，the principle of CO2-crude oil interaction under different pressures was analyzed from two aspects such as dissolution and extraction. Then，CO2 huff and puff experiments were carried out using the de signed core model. At the same time，nuclear magnetic resonance scan was performed on the core before and after displacement and the distribution of remaining oil was analyzed. Finally，combining with the field application in Jiangsu oilfield，the further applica tion direction of CO2 flooding was proposed. Experiment results showed that when the pressure exceeded the threshold value（10.0 MPa），the extraction rate increased significantly with increasing pressure. The extraction rate reached 85.2% at 40.0 MPa. When the pressure was less than the oil-shrinkage value（13.0 MPa），the crude oil exhibited volume expansion with a maximum expansion co efficient of 1.25. When the pressure was greater than 13.0 MPa，the crude oil exhibited a significant volume shrinkage under the strong extraction of CO2. The flooding experiment results showed that for a low permeability matrix core with a length of 6.0 cm， the recovery factor of CO2 huff and puff was 48.0%. During the earlier stage of displacement，the main mechanism of increasing production was oil expansion due to the dissolution of CO2 in crude oil. And during the second stage of displacement，light weight component extracted by CO2 was the main factor. In practical application，the effect of oil reservoir conditions on the interaction be tween CO2 and crude oil should be fully considered. Reservoir with pressure under 15 MPa gave priority to CO2 huff and puff，and that above 15 MPa gave priority to CO2 flooding.

10.19346/j.cnki.1000-4092.2021.03.015