致密油藏渗吸作用影响因素实验——以新疆油田X区块为例

Experiment of influencing factors of imbibition in tight oil reservoir:Taking Block X in Xinjiang Oilfield as an example

致密油藏的经济开发主要依赖于对其储层的大规模体积压裂改造,然而在压裂过程中,压裂液在致密储层间滤失后会发生强渗吸作用,从而影响了压裂增产的效果。整体上,目前业内对致密储层间发生的渗吸作用影响因素的研究不够深入,已有的研究成果不足以支撑致密油藏的高效开发方案的设计工作。以新疆油田X区块为例,通过设计新型高精度电子式全自动静态渗吸测量装置并开展不同压裂液类型、润湿性、温度、界面张力的渗吸室内实验,研究发生在致密岩心中不同影响因素下的渗吸作用。结果表明:新疆压裂常用的滑溜水体系综合渗吸效果明显优于瓜胶体系;润湿性为亲水的岩石更有利于滑溜水发挥渗吸作用;高温下压裂液内部粒子粒径明显增大,导致渗吸采出程度下降;界面张力的变化可以改变渗吸毛管力及洗油效率,其最优值必须通过目的层岩心实验得到,而并非越低越好。为提高该研究区块致密油藏的渗吸采出程度,建议延长闷井时间。研究成果对致密油藏的压裂设计具有一定指导意义。

Economic development of tight oil reservoirs mainly depends on large-scale volumetric fracturing.However,during fracturing process,fracturing fluid may have strong imbibition after filtration between tight reservoirs,influencing stimulation effect.Current research on influencing factors of imbibition between tight oil reservoirs is not thorough enough,and existing research achievements are not enough to support efficient development plans design for tight reservoirs.Taking Block X in Xinjiang Oilfield as an example.imbibition influence by different factors in tight cores is studied by designing a new type of high-precision electronic automatic static imbibition measurement equipment and carrying out imbibition experiments with different fracturing fluid types,wettability,temperatures and interfacial tension.The results show that comprehensive imbibition effect of slickwater system commonly used in fracturing in Xinjiang is obviously better than that of guar gum system.Rocks with hydrophilic wettability are more conducive to imbibition of slickwater.Under high temperature,the particle size of fracturing fluid increases obviously,leading to decrease of imbibition recovery.Change of interfacial tension can change imbibition capillary pressure and displacement efficiency,and optimal value must be obtained through core experiment of target layer,not the lower the better.In order to improve imbibition recovery of tight oil reservoir in studied block,it is suggested to extend soaking time.The research has guiding significance for fracturing design of tight oil reservoirs.