页岩气水平井分段压裂微地震监测认识及应用

Understanding and application of microseism monitoring over staged fracturing in horizontal wells for shale gas development

页岩气水平井分段压裂裂缝的规模形态对单井产能影响较大,研究压裂施工参数及工艺措施对裂缝扩展规模形态的影响规律具有重要指导意义。以JYXXHF井分段压裂为例,采用地面微地震监测技术对该井压裂进行实时监测,并结合地质情况、压裂施工参数及工艺措施等对监测数据进行综合分析。结果表明:该井单段压裂液量达1 600 m^3后缝网轮廓基本形成,1 800m^3后微地震事件几乎不再增加,不同小层微地震事件随压裂液量的变化规律存在一定差异;该井地层埋藏较深,一定量的前置胶有利于增大有效压裂改造体积,中途转注胶,有利于微地震事件数的增加;监测裂缝平均半缝长为160 m,最大为240 m。该分析结果可为该区块页岩气井压裂设计及现场施工提供参考和依据。

Scales and configurations of fractures formed in staged fracturing of horizontal well for shale gas develop- ment may significantly affect productivities of individual wells. Consequently, it is necessary to determine impacts of operation parameters and relevant processes on extension of fractures. With staged fracturing operations in the Well JYXXHF as an example, real-time monitoring for fracturing in the well have been conducted by using surface mi- croseism monitoring techniques. In addition, geologic conditions, fracturing operation parameters and relevant processes have been deployed for comprehensive analyses of monitoring data. Research results show basic fracture networks are basically formed after injection of fracturing fluids with total volume of 1 600 m^3 in one interval. After injection of fluids with volume of 1 800 m^3 , microseism events may hardly increase. In addition, there are certain differences in microseism events in different sublayers with changes in volumes of fracturing fluids injected; Forma- tions encountered in the well have relatively high buried depths. Accordingly, deployment of certain pre-pad may effectively enlarge fracturing area. On the other hand, quantities of microseism events may increase dramatically by transferring to gel injection during the course. Monitoring results show fractures have average half-length of 160 m and maximum half-length of 240 m. Relevant research results may provide necessary references and foundations for design and on-site implementation of fracturing operations in wells for shale gas development.