吉兰泰浅层变质岩储层水平井压裂技术

Horizontal well fracturing for the shallow metamorphic rock reservoir in Jilantai

吉兰泰油田潜山变质岩储层埋藏浅(400~650 m),非均质性强,发育有高角度天然裂缝和底水系统,压裂改造存在压开难度大、底水易沟通、原有工艺适应性差、甜点认识不清等问题。通过分析变质岩储层特征和前期改造经验,确定最佳避水高度100~120 m可实现控水目的;优选桥射联作压裂工艺和25℃低温可溶桥塞,满足大排量、大规模体积压裂需求;优化射孔方位,避射顶部120°,降低出砂风险;优选水溶性暂堵剂,形成层间/层内暂堵工艺,暂堵后压力抬升5~8 MPa;通过远探测声波成像技术明确地质-工程双甜点,形成少段多簇改造模式。在吉华1区块潜山变质岩储层13口井共74段361簇实施压裂作业,较2020年前期试验单井改造段数平均减少2段,压后初期日产油提高48%,截至2022年6月底,累产液超2.66万t,累产油超2.45万t,实现了浅层变质岩储层高效改造和开发。

The buried hill metamorphic rock reservoir of the Jilantai oilfield features shallow burial(400−650 m),high heterogeneity,and the development of high-angle natural fractures and the bottom water system.The fracturing reservoir stimulation suffers from high difficulties in cracking strata,proneness to connection with the bottom water,and blindness for sweet spots.The analysis of the characteristics of the metamorphic rock reservoir combined with the gained fracturing experience showed that the optimal height of water avoidance for water production control is 100−120 m.The bridge plug-perforating integrated technology with the 25℃low-temperature soluble bridge plug was applied to facilitate high-pump-rate large-scale multi-stage fracturing.The perforating azimuth was optimized to avoid perforating the upper 120°range and lower sand production risks.The water-soluble temporary plugging agent was adopted for inter-layer/intra-layer temporary plugging,which led to a pressure rise of 5−8 MPa.The geological-engineering dual sweet spots were identified via long-distance sonic imaging,and the reservoir stimulation model featuring fewer stages and more clusters was formed.The presented fracturing technology was applied to 13 wells of the buried hill metamorphic rock reservoir in the Jihua-1 block,including 74 fracturing stages and 361 perforation clusters.Compared with the testing wells in early 2020,these wells presented the average fracturing stage reduction by 2 stages/well and the growth of initial post-fracturing daily oil production by 48%.By the end of June 2022,the cumulative liquid production exceeded 26600 tons and the cumulative oil production surpassed 24500 tons,which represents high-efficiency reservoir stimulation and recovery of the shallow metamorphic rock reservoir.