李晗^1,2,3,,
姚振兴²
1. 中国科学院地质与地球物理研究所, 中国科学院页岩气与地质工程重点实验室, 北京 100029
2. 中国科学院地球科学研究院, 北京 100029
3. 中国科学院大学, 北京 100049

基金项目: 国家自然科学基金项目（41390455）资助


详细信息

作者简介: 李晗, 男, 1992年生, 博士, 主要从事微地震监测方面研究.E-mail:lihanwy@gmail.com

中图分类号: P315

收稿日期:2017-04-18
修回日期:2017-06-20
上线日期:2018-03-05

Microseismic focal mechanism inversion in frequency domain based on general dislocation point model

LI Han^1,2,3,,
YAO ZhenXing²
1. Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
2. Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China
3. University of Chinese Academy of Sciences, Beijing 100049, China


MSC: P315

--> Received Date: 18 April 2017
Revised Date: 20 June 2017
Available Online: 05 March 2018


摘要
摘要:研究微地震的震源机制，获得压裂区域的破裂方向、尺度和应力状态等信息，在非常规油气开采过程中具有重要意义.对于微震，通常采用剪切位错或者矩张量模型对震源进行描述.本文从其实际发震机制出发，使用了"剪切+张裂"的一般位错点源模型，并基于此模型发展了一种利用全波形信息，通过波形振幅谱相关和初至约束，在频率域求解微震震源机制的方法.该方法适用于地面和井中观测，能够在得到常规震源参数（断层走向、倾角和滑动角）的同时给出裂缝断层剪切和张裂错动的距离信息，更直观体现破裂程度.理论数值测试证明方法有效、可行，在未滤波的情况下，实际数据的波形拟和结果仍较为一致，同时还发现错动距离与应力降等常规破裂参数并不严格相关，说明剪切、张裂错距可作为独立的新参数来定量评估水压致裂效果，指导工程开发进行.
关键词: 微地震监测/
震源机制/
一般位错点源模型/
剪切错距/
张裂错距/
频率域反演

Abstract:Fracture directionality, scale and stress state of hydraulic fracturing areas are extremely important for the exploration of unconventional oil and gas resources. These information can be obtained from the study of microseismic focal mechanisms. For microseismic events, double-couple or moment tensor models are usually used in focal mechanism inversion. In this study, a "Shear & Tensile" general dislocation point model is presented to describe the source of microearthquakes. Based on this model, we develop an approach to calculate microseismic focal mechanism using amplitude spectra fitting and simulated annealing technique in frequency domain. The new method takes account of full waveform information including phase and polarities of first P wave arrivals and can provide dislocation length along each direction as well as common source parameters (strike, dip and rake angles) in the study area. The synthetic tests on surface and borehole network and applications to real data show that our method is robust and efficient. We also find that shear and tensile dislocation lengths are independent of stress drop and can be used as new parameters for quantitative evaluation of hydraulic fracturing.
Key words:Microseismic monitoring/
Focal mechanism/
General dislocation point model/
Shear dislocation/
Tensile dislocation/
Inversion in frequency domain



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