基于微元法的低渗透储层定向射孔转向压裂裂缝动态扩展模型  

Dynamic propagation model for oriented perforation steering fracturing cracks in low permeability reservoirs based on microelement method

作　　者：贺飞飞 张润旭 康天合[1] 康健婷[1] 郭俊庆[1] HE Feifei;ZHANG Runxu;KANG Tianhe;KANG Jianting;GUO Junqing(Key Laboratory of In-situ Property-improving Mining of Ministry of Education,Taiyuan University of Technology,Taiyuan,Shanxi 030024,China)

机构地区：[1]太原理工大学原位改性采矿教育部重点实验室,山西太原030024

出　　处：《岩石力学与工程学报》2020年第4期782-792,共11页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(U1810102);国家自然科学基金青年基金资助项目(41902179)。

摘　　要：为明确低渗透非常规油气储层定向射孔转向压裂改造过程中裂缝扩展轨迹及其偏转距离的变化规律,综合考虑水平地应力差、射孔参数、注液参数、地层力学参数等因素对水力裂缝偏转扩展的影响,建立基于微元法的定向射孔转向压裂裂缝动态扩展模型(MEM模型)。该模型通过VisualBasic语言编制的迭代运算程序完成缝尖微小步长增量与偏转角之间的循环迭代计算,实现对转向裂缝动态扩展过程的模拟。通过比较MEM模型计算的裂缝扩展轨迹与现场压裂微地震监测结果、XFEM模型计算结果及室内压裂试验结果之间的差异,验证MEM模型的准确性。以临兴区块石盒子组致密砂岩储层为例,研究各因素对裂缝扩展轨迹及其偏转距离的影响规律与机制。研究结果表明:不同因素下裂缝扩展轨迹的变化趋势基本一致,裂缝从射孔端起裂后逐渐向水平最大地应力方向偏转,偏转幅度先增大后减小;裂缝偏转距离随水平地应力差的增加呈负对数规律减小,随射孔方位角、注液速率及压裂液黏度的增加呈线性规律增大;射孔长度对裂缝偏转距离几乎没有影响。该模型和结论对进一步认识定向射孔转向压裂过程具有重要意义。In order to clarify the propagation track and the variation rule of deflection distance of fractures during oriented perforation steering fracturing in low permeability unconventional oil and gas reservoirs,a dynamic propagation model for oriented perforation steering fracturing cracks based on microelement method was established by comprehensively considering the influences of horizontal in situ stress difference,perforation parameters,injection parameters and formation mechanical parameters. The model completes the cyclic iteration calculation between the minor step increment and the propagation deflection angle of the crack tip using a calculation program compiled by Visual Basic,and realizes the simulation of the dynamic propagation of steering fractures. The accuracy of the MEM model was verified by comparing the differences among fracture trajectories calculated by MEM model and extended finite element(XFEM) model,micro-seismic monitoring values in the fracturing field and indoor fracturing test results. Taking the tight sandstone reservoir of Shihezi Formation in Linxing block as an example,the influence mechanisms of various factors on the deflection distance of the hydraulic fracture trajectory were studied. The results show that,compared with the XFEM model,the hydraulic fracture trajectory simulated by the proposed model better matches with the micro-seismic monitoring results. The deflection distance decreases negatively logarithmically with increasing horizontal in situ stress difference while increases linearly with increasing the perforated angle,injection rate and viscosity. The perforation length has little effect on the deflection distance. The research work is significant to further understand oriented perforation steering fracturing.

关 键 词：岩石力学 微元法 低渗透储层 定向射孔 转向压裂 裂缝动态扩展模型 

分 类 号：TU45[建筑科学—岩土工程]