微地震监测在非常规气藏压裂转向中的应用

Application of Microseismic Monitoring in Fracture Diversion for Unconventional Gas Reservoirs

摘要: 微地震地面监测技术在非常规气藏压裂施工参数动态调整及暂堵转向时机优化中发挥关键支撑作用。然而，当前基于微地震评价暂堵效果的方法存在局限性：仅依赖暂堵后事件点外延、事件数增加或SRV增长等单一指标易导致误判(统计表明未暂堵段也可能出现类似变化)。研究表明，客观评估暂堵效果需综合三方面参数：1) 暂堵前后微地震事件空间位置迁移特征；2) 暂堵球到位时刻的压力突变响应；3) 后续压裂泵压整体波动形态。本文以川南页岩气藏压裂施工暂堵转向为例，系统阐述了该综合评价方法的应用流程，并指出地面微地震在深层非常规气藏监测中存在信号分辨率不足的缺陷。建议在非常规气藏压裂中融合光纤DAS/DTS技术实时监测各簇进液与加砂状态，结合微地震事件空间演化规律，构建多参数协同的暂堵转向效果评价体系，从而进一步提升评估准确性。

Abstract: Microseismic surface monitoring technology plays a pivotal supporting role in the dynamic adjustment of fracturing operation parameters and the optimization of temporary plugging and diversion timing for unconventional gas reservoirs. However, current methods for evaluating plugging effectiveness based solely on microseismic data exhibit limitations: Relying exclusively on single indicators such as outward extension of event points post-plugging, an increase in event count, or growth in Stimulated Reservoir Volume (SRV) can lead to misjudgment (statistics indicate that similar changes can occur in unplugged intervals). Studies have demonstrated that an objective assessment of plugging effectiveness requires the integration of three key parameters: 1) The spatial migration characteristics of microseismic events before and after plugging; 2) The pressure surge response at the moment diverters reach the target location; and 3) The overall fluctuation pattern of the subsequent fracturing pump pressure. Using temporary plugging and diversion operations in the fracturing of the Southern Sichuan shale gas reservoir as an example, this paper systematically details the application workflow of this comprehensive evaluation method. It further points out the limitations of surface microseismic monitoring for deep unconventional reservoirs due to inadequate signal resolution. To enhance the accuracy of plugging effectiveness evaluation, it is recommended to integrate fiber optic Distributed Acoustic Sensing (DAS) and Distributed Temperature Sensing (DTS) technologies during unconventional reservoir fracturing. This enables real-time monitoring of fluid intake and proppant placement status per cluster. Combined with the spatial evolution patterns of microseismic events, a multi-parameter collaborative evaluation system for temporary plugging and diversion effectiveness should be established.