一种改进的声发射模板识别流程及其在大尺度页岩水力压裂主被动观测实验中的应用研究  

A new template matching based acoustic emission detection procedure and its application in laboratory hydraulic fracturing experiment

作　　者：李德康 贺正然 张作冬 邹雨时[3] 王小琼[3] 谢凡[1] LI De Kang;HE ZhengRan;ZHANG ZuoDong;ZOU YuShi;WANG XiaoQiong;XIE Fan(Key Laboratory of Earthquake Source Physics,Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;School of Information Science and Engineering,Southeast University,Nanjing 210096,China;Unconventional Petroleum Research Institute,China University of Petroleum,Beijing 102249,China)

机构地区：[1]中国地震局地球物理研究所震源物理重点实验室,北京100081 [2]东南大学信息科学与工程学院,南京210096 [3]中国石油大学(北京)非常规油气科学技术研究院,北京102249

出　　处：《地球物理学报》2023年第10期4386-4401,共16页Chinese Journal of Geophysics

基　　金：国家重点研发计划项目(2020YFA0710600);国家自然科学基金项目(41874061)资助。

摘　　要：提出一种改进的实验室声发射模板识别流程.该流程联合RMS-AIC算法优化了模板事件的检测效果,将一种改进的绝对离差中位数(观测数据的二分位数与MAD的和)应用于不同时段RMS与互相关序列的动态阈值的设置中,并对声发射模板事件与多通道连续波形数据的互相关叠加方式进行了改进,以避免弱初至延迟量不准确对叠加异常点的影响.我们开展了大尺度龙马溪组页岩水力压裂过程的主动源超声检测与声发射事件联合观测实验,并将该流程应用于主、被动连续观测数据中声发射信号的识别.研究结果表明:利用本文提出的流程检测出1720个声发射信号,数量比声发射模板信号大约多5.54倍.利用更为完备的声发射目录,我们观测到页岩水力压裂过程中的主压裂点大约发生在152 s,且压裂后早期3 s内声发射率呈现出较慢的幂率衰减(p=0.130),而后以较快速率(p=1.403)衰减至稳定值.此外,我们对多种震相拾取算法的比较、声发射的频-幅分布特征等方面开展了讨论.这一新的声发射识别流程可以有效提高在主、被动联合观测下的声发射识别效果,完备水力压裂过程中声发射的时序分布特征,为页岩气开采及风险评估的实验室研究提供有效支撑.We introduce a new template matching-based procedure to detect acoustic emissions(AEs)using multi-channel continuous passive records associated with active ultrasonic during the laboratory hydraulic fracturing experiment.The procedure consists of two features including(1)an improved RMS-AIC-based method to construct the template catalog and(2)a dynamic threshold of median absolute deviation which can effectively detect AE events from both multi-channel RMS and CC(cross-correlation)series acquired from the template matching method.In addition,a new stacking procedure during template matching is also proposed to improve the inaccurate onset of the weak AE due to the temporal evolving signal-to-noise ratio with respect to the channels.By analyzing the six-channel continuous passive data recorded from the hydraulic fracturing experiment on a shale specimen(30 cm×30 cm×30 cm)under triaxial stresses,we successfully detect 1720 AE signals using the new procedure during the experiment.It is about 5.54 times larger than the number of the template AE signals detected by the RMS-AIC-based method.With the more complete AE catalog,we further analyze the damage evolving of the shale sample before and after the breakdown associated with the fluid-induced fractures by using the activity of AEs.The results suggest the pressure breakdown point during the hydraulic fracturing occurs at~152 s,and a slow-to-fast power-rate decay from p=0.130 to p=1.403 in AE rate is observed after the breakdown.We discuss the results by(1)comparing with other AE detecting methods,and(2)characterizing the frequency-and amplitude-dependent features of detected AE during the hydraulic fracturing experiment.The new procedure can improve the understanding of damage evolving of the shale specimen under laboratory hydraulic fracturing experiments.

关 键 词：模板匹配 水力压裂 主、被动连续记录 声发射活动性 频-幅特征 

分 类 号：P313[天文地球—固体地球物理学] P631[天文地球—地球物理学]