| 储集层中高压流体引爆强地震的机理——以5.12汶川地震为例 |
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| 引用本文： | 毛小平,何廉康,刘佳林,李岁岁,张学强,宿宇驰,卢鹏宇.储集层中高压流体引爆强地震的机理——以5.12汶川地震为例[J].地质力学学报,2021,27(4):628-642. |
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| 作者姓名： | 毛小平 何廉康 刘佳林 李岁岁 张学强 宿宇驰 卢鹏宇 |
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| 作者单位： | 中国地质大学 (北京) , 北京100083;中国地质大学 (武汉) , 武汉430074 |
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| 基金项目： | 中国石油化工股份有限公司科技项目（No.JP14009） |
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| 摘 要： | 目前产生地震的机制仍以弹性回跳说为主:地震是因为断层错断使岩层的弹性能释放而引发。但越来越多的学者开始质疑，仅断层错断后的弹性能，是否真能达到实际地震所释放的巨大能量。因此，有必要探讨地震初动后破坏性强震的性质及其真正的能量来源。文章根据沉积地层中的储集层及其压力的特点分析得出，储集层内含有大量的高压流体，其压力在一定条件下可以释放出来，产生流体物理爆炸，有可能是强震能量的重要组成部分。通过计算得出，当断层破裂并刺穿面积较大的储集层时，其压力释放所产生的弹性能可以达到震级8.0以上地震所释放的能量；人为的工程活动也可引发小规模的流体压力的释放现象，如钻井时的井喷、水力压裂会诱发有感地震等。同时，文章根据对距离震中较近的地震台的波形及传播射线路径分析认为，强震波动可能不是横波S波，而是涨缩波P波，据此不能排除强震是由爆炸所致。综合汶川地震多个台站记录到的地震波的时间域和频率域特征、地面观测到的爆炸现象、地震后科学钻探获得的岩心等大量直接或间接证据，说明了这种流体爆炸能量释放的可能性。最后，文章提出了地震活动可分为三个阶段:微破裂阶段Ⅰ，该阶段有流体活动，并可产生动电效应，但未触发地震初动；地震初动后的断裂破裂阶段Ⅱ；由流体压力释放产生地震强震阶段Ⅲ。
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| 关 键 词： | 汶川地震 时频分析 起始破裂 初动 储集层 流体超压 |
| 收稿时间： | 2021/4/5 0:00:00 |
| 修稿时间： | 2021/7/16 0:00:00 |
Mechanism of the strong earthquake triggered by high pressure fluid in reservoir: A case study of the 5.12 Wenchuan earthquake |
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| MAO Xiaoping,HE Liankang,LIU Jialin,LI Suisui,ZHANG Xueqiang,SU Yuchi,LU Pengyu.Mechanism of the strong earthquake triggered by high pressure fluid in reservoir: A case study of the 5.12 Wenchuan earthquake[J].Journal of Geomechanics,2021,27(4):628-642. |
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| Authors: | MAO Xiaoping HE Liankang LIU Jialin LI Suisui ZHANG Xueqiang SU Yuchi LU Pengyu |
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| Institution: | 1.School of Energy Resource, China University of Geoscience, Chengfu Road 20, Haidian District, Beijing 100083, China2.School of Earth Exploration and Information Technology, China University of Geosciences (Wuhan), Lumuo Road, Hongshan District, Wuhan 430074, China |
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| Abstract: | At present, the mechanism of earthquake is still based on elastic rebound theory—Earthquake is caused by the release of elastic energy of rock strata due to fault dislocation. But more and more scholars began to question whether the elastic energy after fault faulting can really reach the huge energy released by the actual earthquake. Therefore, it is necessary to study the nature of destructive strong earthquake and its real energy source after the initial movement. According to the characteristics of the reservoir and its pressure in the sedimentary strata, it is concluded that there are a lot of high-pressure fluid in the reservoir, and its pressure can be released under certain conditions, resulting in fluid physical explosion, which may be an important part of strong earthquake energy. The calculation results show that when the fault ruptures and penetrates the reservoir with large area, the elastic energy produced by the pressure release can reach the energy released by the earthquake with magnitude above 8.0; Artificial engineering activities can also lead to the release of small-scale fluid pressure, such as blowout during drilling, earthquake induced by hydraulic fracturing, etc. At the same time, according to the analysis of the waveforms and propagation ray paths of the seismic stations close to the epicenter, it is considered that the strong earthquake wave may not be S-wave, but P-wave. Therefore, it cannot be ruled out that the strong earthquake might be caused by explosion. A large number of direct or indirect evidence, such as the time domain and frequency domain characteristics of seismic waves recorded by several stations during the Wenchuan earthquake, the explosion phenomena observed on the ground, and the cores obtained by scientific drilling after the earthquake, indicate the possibility of the release of this kind of fluid explosion energy. Finally, this paper proposes that the seismicity can be divided into three stages: The stage Ⅰ of micro rupture, in which there is fluid activity and electrokinetic effect, but the initial earthquake motion is not triggered; The stage Ⅱ of fault rupture after the initial earthquake motion; The strong earthquake stage Ⅲ, which is caused by the release of fluid pressure. |
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| Keywords: | Wenchuan earthquake time frequency analysis initial fracture initial motion reservoir fluid overpressure |
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