川南深层页岩压裂裂缝导流能力测试技术

Measurement of the conductivity of induced fractures in the deep shale in Southern Sichuan basin

随着埋深增加,深层页岩压裂后,裂缝导流能力能否有效保持是个关键问题。以川南龙马溪组深层页岩为例,对比测试了支撑裂缝及自支撑裂缝的导流能力,开展了主控因素影响规律分析及适应性评价。结果表明,应力增加,支撑裂缝及自支撑裂缝导流能力均呈指数式下降;支撑裂缝受粗糙度、铺砂浓度、支撑剂类型、粒径等影响,在低铺砂浓度下受裂缝面粗糙度主控,在高铺砂浓度下受支撑剂铺置主控;自支撑裂缝受裂缝产状、粗糙度、滑移量、力学性质等影响;对深层页岩而言,垂直自支撑裂缝、石英砂及覆膜砂铺置的支撑裂缝满足生产初期需求,陶粒铺置的支撑裂缝更有利于生产后期的导流能力保持。形成的压裂缝导流能力测试方法可为深层页岩的压裂优化设计提供借鉴。

Whether the conductivity of induced fractures keeps stable as the burial depth of shale formation increases is very important.Taking the deep shale of the Longmaxi Formation in the southern Sichuan Basin as a case,this paper compares the conductivity of the supported fractures and the self-supporting fractures,and analyzes the influencing law of control factors and adaptability.The results show that the conductivity of the supported fractures and self-supporting fractures decreases exponentially with increasing stress;supported fractures are affected by their roughness,proppant concentration,proppant type,particle size,etc.;at low proppant concentration,fracture roughness is a dominant factor,while at high proppant concentration,proppant placement is dominant;self-supporting fractures are affected by fracture occurrence,roughness,slippage,mechanical properties,etc.In the deep shale,vertical self-supporting fractures,and the fractures supported by quartz sand and coated sand meet the requirement of initial production,and the fractures supported by ceramsite are more effective to maintain the conductivity in later production.The method for testing fracture conductivity is a reference to designing deep shale fracturing stimulation.