致密砂岩油藏CO2灌注提高混相程度研究

CO2 perfusion to improve degree of miscibility in tight sandstone reservoir

关键词:  致密砂岩油藏  CO₂非混相驱  CO₂灌注  混相程度

Key words:  tight sandstone reservoir  CO₂ immiscible flooding  CO₂ perfusion  degree of miscibility

摘要:

目的 基于快速补充地层能量可实现提高CO₂混相程度的技术原理，对灌注法提高鄂尔多斯盆地低压致密砂岩油藏CO₂非混相驱混相程度的可行性进行研究。方法 采用室内实验方法，在油藏条件下比较不同注入流量、注入量的CO₂驱油效果，考查了地层压力、换油率、采出程度、气油比及抽提参数的变化。结果 与常规注入流量和注入量相比，灌注后地层压力增加4.14 MPa，换油率增加0.13，采出程度提高22%，气油比降低50%， C₄~C₁₂的组分含量明显增加，重组分的含量明显减少。2个井组现场试验表明，相比灌注前，井组月产油增加78%，平均地层压力5 MPa，对应油井的油压提升了4.5 MPa，混相程度提高了32.81%，驱油效果显著。结论 灌注法可有效提高CO₂驱混相程度，能够改善致密砂岩油藏储层CO₂非混相驱油效果。

Abstract:

Objective Based on the technical principle that rapid replenishment of formation energy can improve the degree of CO₂ miscibility, the feasibility of the injection method to improve the degree of CO₂ immiscible flooding in low-pressure tight sandstone reservoirs in Ordos Basin was studied. Methods In this paper, the effects of CO₂ displacement at various injection rates and volumes were compared under reservoir conditions. The changes of formation pressure, oil change rate, recovery degree, gas-oil ratio and extraction parameters also were investigated. Results Compared with the conventional injection rate and volumes, the formation pressure increased by 4.14 MPa, the oil change rate increased by 0.13, the recovery degree increased by 22%, the gas-oil ratio decreased by 50%, the component content of C₄—C₁₂ increased significantly, and the content of recombination component decreased significantly. Field tests of the two well groups showed that the monthly oil production of the well group was increased by 78%, the average formation pressure was 5 MPa, the corresponding well oil pressure was increased by 4.5 MPa, the degree of miscibility was increased by 32.81%, and the oil displacement effect was remarkable. Conclusion The injection method can effectively improve the degree of CO₂ miscible flooding and the effect of CO₂ immiscible flooding in tight sandstone reservoirs.