Side-by-side Chinese-English

正交各向异性介质中的剪张源震源机制与矩张量特征

唐杰1 温雷1 王浩1 张文征1

(1.中国石油大学 (华东) 地球科学与技术学院, 山东青岛 266580)

【摘要】水力压裂区在整体上呈现各向异性特征, 深入研究和分析水力压裂区的各向异性参数对震源机制和矩张量的影响成为必要。本文研究了干燥和完全饱水垂直正交裂缝介质的地震波响应特性, 通过各向异性介质参数和源张量获得各向异性介质中的微地震矩张量, 分析了震源区各向异性对双力偶分量 (DC) 、补偿线性偶极子分量 (CLVD) 和各向同性分量 (ISO) 的影响, 并对比了裂缝及其所含流体的特征参数对地震波响应特性的影响效果。研究结果表明:各向异性介质中由于剪张破裂产生的非DC分量依赖于破裂方式、各向异性介质的类型、裂缝参数及断面方向等, 干燥裂纹介质中的ISO分量较高, 水饱和裂纹介质中产生较高的CLVD分量、而ISO较小;各向同性与各向异性介质中剪张源的远场P波辐射花样存在差异, 震源特征和介质各向异性会对地震波走时、极性和振幅产生明显影响。探究水力压裂区各向异性参数对震源机制的影响效果对微地震震源描述具有重要意义。

【关键词】 正交各向异性;微地震;震源机制;地震矩张量;剪张源;

【DOI】

【基金资助】 国家自然科学基金项目 (41504097, 41874153) 资助;

Focal mechanism and moment tensor in orthorhombic anisotropic media

TANG Jie1 WEN Lei1 WANG Hao1 ZHANG Wenzheng1

(1.School of Geosciences, China University of Petroleum (East China) , Qingdao, Shandong, China 266580)

【Abstract】Hydraulic fracturing zones have anisotropic characteristics on the whole. It is necessary to analyze the influences of anisotropic parameters on focal mechanism and moment tensor. This paper studies the shear–tensile focal mechanism and seismic moment tensor when the source is located in anisotropic media. It analyzes the influences of focal anisotropy on double couple (DC) components, compensated linear vector dipole (CLVD) components, and isotropic (ISO) components. The seismic response characteristics of dry and saturated orthorhombic anisotropy media are also analyzed. The effects of crack parameters and fluid parameters on seismic response are discussed. The following results are obtained based on our research. A. The moment tensor in anisotropic media can be obtained by anisotropic parameters and source quantity. B. The non-DC components caused by shear–tensile crack depend on the rupture mode, type of anisotropic media, crack parameter and section strike. High ISO components appear in dry cracked media and high CLVD components appear in water saturation media. C. Far field P-wave radiation patterns are different between isotropic and anisotropic media. The source characteristics and medium anisotropy have significant impacts on the seismic wave travel time, amplitude, and polarity.

【Keywords】 orthorhombic anisotropy; microseismic; focal mechanism; moment tensor; shear–tensile source;

【DOI】

【Funds】 National Natural Science Foundation of China (41504097, 41874153);

Download this article
    References

    [1] Rong Jiaojun, Li Yanpeng, Xu Gang et al. Fracture detection with microseismic. OGP, 2015, 50 (5): 919–924 (in Chinese).

    [2] Fang Bing, Sun Chengyu, Tang Jie et al. Analysis of frequency characteristics of micro–seismic signals. OGP, 2015, 50 (3): 411–417 (in Chinese).

    [3] Tang Jie, Wang Hao, Wen Lei et al. Focal mechanism of shear–tensile microseismic and amplitude distribution characteristics. OGP, 2018, 53 (3): 502–510 (in Chinese).

    [4] Cai Xiaogang, Yao Chen, Chen Xiaofei. Seismic moment tensor in anisotropic ATI media: shear faulting. Chinese Journal of Geophysics, 2011, 54 (7): 1772–1782 (in Chinese).

    [5] VavryCuk V. Focal mechanisms in anisotropic media. Geophysical Journal International, 2005, 161 (2): 334–346.

    [6] VavryCuk V. Focal mechanisms produced by shear faulting in weakly transversely isotropic crustal rocks. Geophysics, 2006, 71 (5): 145–151.

    [7] Chapman C H, Leaney S. A new moment-tensor decomposition for seismic events in anisotropic media. Geophysical Journal International, 2014, 199 (3): 1808–1810.

    [8] Leaney W S. Microseismic Source Inversion in Anisotropic Media [D]. University of British Columbia, 2014.

    [9] Tomas F, Alice G. Shear and tensile earthquakes caused by fluid injection. Geophysical Research Letters, 2011, 38 (5): 387–404.

    [10] Tsvankin I, Gaiser J, Grechka V. Seismic anisotropy in exploration and reservoir characterization: An overview. Geophysics, 2010, 75 (5): 15–29.

    [11] Sil S,Sen M,Gurevich B. Analysis of fluid substitution in a porous and fractured medium. Geophysics, 2011, 76 (3): 157–166.

    [12] Tang Jie, Fang Bing, Sun Chengyu et al. Study of seismic wave propagation characteristics based on anisotropic fluid substitution in fractured medium. GPP, 2015, 54 (1): 1–8 (in Chinese).

    [13] Schoenberg M, Sayers C. Seismic anisotropy of fratured rock. Geophysics, 1995, 60 (1): 204–211.

    [14] Krief M, Garat J, Stellingwerff J et al. A petrophysical interpretation using the velocities of P and S waves (full-waveform sonic). Log Analyst, 1990, 31 (6): 355–369.

    [15] Huang L, Stewart R, Sil S et al. Fluid substitution effects on seismic anisotropy. Journal of Geophysical Research. 2015, 120 (2): 850–863.

    [16] Sayers C M, Kachanov M. Microcrack-induced elastic wave anisotropy of brittle rocks. Journal of Geophysical Research, 1995, 100 (3): 4149–4156.

    [17] Gurevich B. Elastic properties of saturated porous rocks with aligned fractures. Journal of Applied Geophysics, 2002, 54 (3): 203–218.

    [18] Vavrycuk V. Tensile earthquakes: Theory, modeling, and inversion. Journal of Geophysical Research, 2011, 116 (12): B12320.

    [19] Vavrycuk V. Moment tensor decompositions revisited. Journal of Seismology, 2015, 19 (1): 231–252.

    [20] Vavrycuk V. Inversion for anisotropy from non-double-couple components of moment tensors. Journal of Geophysical Research, 2004, 109 (7): 632–641.

    [21] Grechka V. Tilted TI models in surface microseismic monitoring. Geophysics, 2015, 80 (6): 11–23.

    [22] Hudson J A, Pearce R G, Rogers R M. Source type plot for inversion of the moment tensor. Journal of Geophysical Research Atmospheres, 1989, 94 (1): 765–774.

    [23] Aki K, Richards P G. Quantitative Seismology. University Science Books, 2002, Sausalito, CA, USA.

    [24] Tang Jie, Fang Bing, Sun Chengyu et al. Study on focal mechanism of micro-seismic induced by hydrofracture and signal propagation characteristics. OGP, 2015, 50 (4): 643–649 (in Chinese).

    [25] Yao ZhenJan, Sun Chengyu, Tang Jie et al. Micro-seismic forward modeling in viscoelastic anisotropic media based on different focal mechanisms. OGP, 2017, 52 (1): 63–70 (in Chinese).

This Article

ISSN:1000-7210

CN: 13-1095/TE

Vol 53, No. 06, Pages 1247-1255+1114

December 2018

Downloads:0

Share
Article Outline

Abstract

  • 1 Introduction
  • 2 Shear-tensile source model in orthorhombic anisotropic media
  • 3 Characteristics of the source in orthorhombic anisotropic media
  • 4 Characteristics of microseismic wave field in orthorhombic anisotropic media
  • 5 Conclusions
  • References