CO_2复合开发技术在低渗透油藏中的应用

The application of CO_2 composite development technology in low permeability reservoir

苏北油田阜宁组低渗油藏具有油层薄、渗透率低、物性差，储量品位低，开发中存在产量低、递减快、注采井网不完善、易水淹、采出程度低等特点，为此开展了多水平井、压裂、CO2吞吐、CO2驱油的CO2复合开发技术研究及矿场试验。数值模拟发现5段裂缝水平井中CO2波及范围是直井的4．7倍，注CO2后水平井井筒附近含油饱和度上升5．4％。用数模对金南CO2复合开发技术的关键参数进行优化，增油量890～2230t，平均CO2换油率为1．08t油／tCO2，比前期直井CO：吞吐的换油率提高了107．7％，井组控制储量提高采收率3．19％。复合开发技术有较好经济效益，40$／B油价下，22天即可收回措施成本投资，在50$／B油价下，就可使开发单元从边际有效区进入到盈利高效区，这种开发模式对小断块低渗透油藏具有广阔的应用前景。

Funing formation of Subei oilfield is a low permeability reservoir, which has the characteristics of thin oil layer, low permeability, poor physical property, low grade reserve, low production, fast decline of production, imperfect injection-production well pattern, easily water flooding and low degree of reserve recovery, accordingly, the study and field test of CO2 composite development technology which includes horizontal wells, fracturing, CO2huff and puff, oil displacement by CO2 are carried out. By adopting numerical analogue technology, the result shows that, in five fractured horizontal wells, sweep area of CO2 is 4.7 times higher than vertical wells, and oil saturation near horizontal wellbore rises 5.4 % after injecting CO2. After key parameters optimized by CO2 composite development technology in Jinnan block, oil increment reached 890 - 2 230 t, average oil draining ratio was 1.08 t oil/t COs, which was increased by 107.7 % than vertical wells, and oil recovery of reserve controlled by single well enhanced 3.19 %. Due to the good economic effects of CO2 composite development technology, investment can be recovered within 22 days at the crude oil price of 40 $/B and it will gain high profits if price is 50 $/B. This kind of development pattern will have broad application prospect in low permeability reservoir of small fault block.