南海某区块保护储层自降解防漏堵漏钻井液技术研究

Study on self-degradation drilling fluid for reservoir protection in a block of South China Sea

针对南海某区块裂缝性储层漏失与保护储层技术难题,通过岩性分析与扫描电镜测试,分析了目标区块储层主要损害机理,并通过选用新型环氧树脂自降解堵漏剂,优化粒度级配准则,优选防水锁剂,构建了保护储层自降解防漏堵漏钻井液体系。试验结果表明,目标区块储层裂缝发育,主要岩性为花岗岩,储层损害方式为固相侵入与水锁损害,选用的新型自降解防漏堵漏剂,120℃条件下96 h降解率大于95%,优化粒度级配准则为D90时其裂缝封堵承压能力达7.6 MPa,同时优选的防水锁剂SDFS-1的水锁损害率仅为15.24%。以此构建的自降解防漏堵漏钻井液体系具有良好的裂缝封堵承压能力,封堵层突破压力超过11 MPa,同时储层保护试验结果显示,目标区块地层岩心渗透率恢复率均达到90%以上,具有良好的裂缝封堵与储层保护效果。

In view of the technical problems of leakage and reservoir protection of fractured reservoirs in a block in the South China Sea,the main damage mechanism of reservoir in the target block is analyzed through lithological analysis and scanning electron microscope testing.By selecting a new type of epoxy resin self-degradation plugging agent,optimizing the particle size gradation criterion,and optimizing the waterproof locking agent,a self-degradation drilling fluid system for reservoir protection,leakage prevention and plugging is constructed.The results show that the reservoir fractures in the target block are developed,the main lithology is granite,and the reservoir damage mode is solid phase invasion and water lock damage.The selected new self-degradation leak prevention and plugging agent has a degradation rate of more than 95%in 96 h at 120℃.When the optimized particle size gradation criterion is D90,its fracture sealing pressure bearing capacity can reach 7.6 MPa.At the same time,the optimized waterproof locking agent SDFS-1 has a water lock damage rate of only 15.24%.The self-degradation leak prevention and plugging drilling fluid system constructed on this basis has good fracture sealing and pressure bearing capacity,and the breakthrough pressure of the plugging layer exceeds 11 MPa.The reservoir protection experiment results show that the core permeability recovery rate of the target block formation can reach more than 90%,which has good fracture sealing and reservoir protection effects.