低渗透裂缝性油藏两级封窜扩大波及体积技术

Enlargement Swept Volume Technology by Two Stages Sealing in Low Permeability Reservoirs with Cracks

为降低低渗透油藏CO2驱油过程中窜逸现象的发生,选取低渗二维饼状岩心,用压裂设备逐渐加压对岩心造裂缝,采用反五点法模拟超前注水后低渗透油藏的开发,进行改性淀粉凝胶封堵裂缝后水驱、乙二胺封堵气窜通道后CO2驱两级封窜实验。结果表明,改性淀粉凝胶可有效封堵地层中的裂缝,水驱及改性淀粉凝胶一级封窜裂缝后的采收率为23.4%;一次CO2驱期间出现气窜,但气窜阶段仍是提高采收率的重要阶段,一次CO2驱的采收率为21.3%;乙二胺可有效封堵低渗层气窜通道,扩大CO2波及体积,乙二胺二级封窜后CO2驱采收率为15.0%。在反五点法岩心物理模拟实验中,水驱及水驱后改性淀粉凝胶一级封窜地层中裂缝+CO2非混相驱后乙二胺二级封窜气窜通道的采收率为59.6%,增油效果明显。

In order to reduce the occurrence of different degrees of CO2 channeling during the CO2 flooding in low permeability reservoirs,the low-permeability and heterogeneous plane-section cores were selected,and large cracks and micro-cracks were created in the cores.The anti-five-point method was used to carry out the water flooding and CO2 immiscible flooding experiments.The development after water flooding were simulated.Two-stage sealing experiment were carried,which was CO2 flooding after water flooding with modified starch gel plugging cracks and C2H8N2 blocking gas channel.The experiment results showed that modified starch gel could block cracks in the formation,and the recovery rate of water flooding was 23.4%.Gas channeling occurred during the first CO2 flooding,but gas channeling was still an important stage to enhance recovery.The recovery rate of first CO2 flooding was 21.3%.C2H8N2 could block gas channeling effectively and increase the volume of the sweep.The recovery rate of second CO2 flooding after C2H8N2 sealing was 15.0%.In the anti-five-point core physics simulation experiment,modified starch gel’s first-stage sealing after water flooding and C2H8N2 second sealing after CO2 flooding had 59.6%recovery rate,indicating obvious oil increment.