二维电阻率倾斜各向异性对海洋可控源电磁场响应的影响
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摘要
地下介质的电阻率常常表现为各向异性,海底褶皱带、逆冲断层带和倾斜层状沉积序列等地质构造可能形成宏观电阻率倾斜各向异性。这里采用规则矩形网格剖分有限元法,实现了二维电阻率倾斜各向异性海洋可控源电磁(CSEM)正演算法,模拟了二维电阻率倾斜各向异性模型海洋可控源电磁场响应。模型计算结果表明,电阻率倾斜各向异性围岩对含有海底高阻薄层的海洋可控源电磁响应产生严重畸变影响。因此,在海洋电磁资料解释中,电阻率倾斜各向异性的影响应该得到重视,忽略该影响将可能会导致数据解释错误。
Subsurface medium tends to exhibit resistivity anisotropy. Geologic structures such as submarine fold belt, thrust fault zone and tilted stratified sedimentary sequence are likely to form an environment shows macroscopic tilted transverse isotropy(TTI) in resistivity. In this paper, we developed a 2 D finite-element(FE) modeling algorithm on rectangle mesh, allowing for modeling of the EM field components over arbitrary 2 D tilted resistivity anisotropy models typical for marine CSEM applications. According to simulations, the impact of TTI anisotropy on marine CSEM measurements was assessed using TTI and VTI benchmark models. The model calculation results indicate that tilted transverse isotropic surrounding rock may produce distortion on electromagnetic response of thin resistive layer in the submarine sediments. Thus, the tilted anisotropy should be valued during interpretation of field data. Ignoring the TTI effect, if it is present, might lead to erroneous assessments and compromise the reliability of marine CSEM technology.
Subsurface medium tends to exhibit resistivity anisotropy. Geologic structures such as submarine fold belt, thrust fault zone and tilted stratified sedimentary sequence are likely to form an environment shows macroscopic tilted transverse isotropy(TTI) in resistivity. In this paper, we developed a 2 D finite-element(FE) modeling algorithm on rectangle mesh, allowing for modeling of the EM field components over arbitrary 2 D tilted resistivity anisotropy models typical for marine CSEM applications. According to simulations, the impact of TTI anisotropy on marine CSEM measurements was assessed using TTI and VTI benchmark models. The model calculation results indicate that tilted transverse isotropic surrounding rock may produce distortion on electromagnetic response of thin resistive layer in the submarine sediments. Thus, the tilted anisotropy should be valued during interpretation of field data. Ignoring the TTI effect, if it is present, might lead to erroneous assessments and compromise the reliability of marine CSEM technology.
引文
[1] KAREN WEITEMEYER S.C.A.K..Marine em techniques for gas-hydrate detection and hazard mitigation[J].The Leading Edge,2006,25(5):629-632.
[2] LI Y.,LUO M.,JIANXIN P..Adaptive finite element modeling of marine controlled-source electromagnetic fields in two-dimensional general anisotropic media[J].J.Ocean Univ.China,2013,1-5(12 (1)):1672-5182.
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[17] 胡祥云,霍光谱,高锐,等.大地电磁各向异性二维模拟及实例分析[J].地球物理学报,2013,56(12):4268-4277.HU X Y,HUO G P,GAO R,et al.The magnetotelluric anisotropic two dimensional simulation and case analysis[J]Chinese Journal of Geophysics,2013,56(12):4268-4277.(In Chinese)
[18] HERREDSVELA J.,COLPAERT A.,Foss S.K.et al.Feasibility of electromagnetic methods for sub-basalt exploration[C].82nd Annual International Meeting,SEG,Expanded Abstracts,2012:1-5.
[19] ZACH J.J.,FRENKEL M.A..3d inversion-based interpretation of marine CSEM data[J].SPE Journal of Reservoir Evaluation and Engineering,2012,15(3):321-334.
[20] 罗鸣,李予国,李刚.一维垂直各向异性介质频率域海洋可控源电磁资料反演方法[J].地球物理学报,2016,59(11):4349-4359.LUO M,LI Y G,LI G.Frequency domain inversion of marine csem data in one dimensional vertically anisotropic structures[J].Chinese Journal of Geophysics,2016,59(11):4349-4359.(In Chinese)
[21] 赵宁,王绪本,秦策.基于vti各向异性介质的频率域海洋可控源电磁三维约束反演[J].地球物理学报,2017,60(5):1946-1954.ZHAO N,WANG X B,QIN C.3D frequency domain mcsem constrained inversion in vti media[J].Chinese Journal of Geophysics,2017,60(5):1946-1954.(In Chinese)
[22] BAKULIN A.,WOODWARD M.,OSYPOV K,et al.Can we distinguish tti and vti media.Meeting[J].SEG,2007:226-230.
[23] FRENKEL M.A.,FEHLER M.Seam update,phase i - rpsea update:controlled-source electromagnetic simulations[J].The Leading Edge,2012,31(9):1012-1014.
[24] YUJI MITSUHATA.2-D electromagnetic modeling by finite-element method with a dipole source and topography[J].Geophysics,2000,65(2):465-475.
[25] LI Y,KEY K.2D marine controlled-source electromagnetic modeling:Part 1 — An adaptive finite-element algorithm[J].Geophysics,2007,72(2):WA51.
[26] AMESTOY P.R.,DUFF I.S.,L’EXCELLENT JY,et al.MUMPS:A General Purpose Distributed Memory Sparse Solver.Conference paper,2001,121-130.
[27] CONSTABLE S.Ten years of marine CSEM for hydrocarbon exploration[J].Geophysics,2010,73(5):75A67.
[2] LI Y.,LUO M.,JIANXIN P..Adaptive finite element modeling of marine controlled-source electromagnetic fields in two-dimensional general anisotropic media[J].J.Ocean Univ.China,2013,1-5(12 (1)):1672-5182.
[3] LI Y.,DAI S.,.Finite element modelling of marine controlled-source electromagnetic responses in two-dimensional dipping anisotropic conductivity structures[J].Geophysical Journal International,2011,2(185):622-636.
[4] 吴能友,杨胜雄,王宏斌,等.南海北部陆坡神狐海域天然气水合物成藏的流体运移体系.地球物理学报,2009,52(6):1641-1650.WU N Y,ZHANG H Q,YANG S X,et al.Preliminary discussion on natural gas hydrate reservoir systemof shenhu area north slope of south china sea[J].Natural Gas Ind,2007 ,27(9):1-6.(In Chinese)
[5] 肖安成,李启明,董大忠.中国西北含油气盆地周缘滑脱逆冲褶皱带中的油气聚集.1998,18(1):60-65.XIAO A C,LI Q M,DONG D Z.Oil and gas accumulation in thrust-fold belts of northwest oil-bearing basins,China[J].J Mineral Petrol,1998,18(1):60- 65.(In Chinese)
[6] COLOMBO D.,MCNEICE G.,CURIEL E.S.et al..Full tensor CSEM and mt for subsalt structural imaging in the red sea:implications for seismic and electromagnetic integration[J].The Leading Edge,2013,32(4):436-449.
[7] ANDREY B.,MARTA W..Building tilted transversely isotropic depth models using localized anisotropic tomography with well information[J].Geophysics,2010,75(4):D27-D36.
[8] STEFANI J.,FRENKEL M.A.,BUNDALO N.et al..Seam update:models for em and gravity simulations[J].The Leading Edge,2010,29(2):1178-1180.
[9] FRENKEL M.A.,DAVYDYCHEVA S..To CSEM or not to CSEM feasibility of 3d marine CSEM for detecting small targets[J].The Leading Edge,2012,31(4):435-447.
[10] DAVYDYCHEVA S.DRUSKIN V.Staggered grid for maxwell's equations in 3-d anisotropic media[J].Meeting,SEG,1999:138-145.
[11] KONG F.,JOHNSTAD S.,R?STEN T,et al.A 2.5d finite-element-modeling difference method for marine CSEM modeling in stratified anisotropic media[J].Geophysics,2007,73(1):F9-F19.
[12] L?SETH L.O.,Ursin B.,Electromagnetic fields in planarly layered anisotropic media[J].Geophysical Journal International,2007,170(1):44-80.
[13] 刘颖,李予国.层状各向异性介质中任意取向电偶源的海洋电磁响应[J].石油地球物理学报,2015,50(4):755-765.LIU Y,LI Y G.Marine controlled-source electromagnetic fields of an arbitrary electric dipole over a layered anisotropic medium[J].Chinese Journal of Geophysics,2015,50(4):755-765.(In Chinese)
[14] 陈桂波,汪宏年,姚敬金 ,等.各向异性海底地层海洋可控源电磁响应三维积分方程法数值模拟[J].物理学报,2009,58(6):1000-3290.CHEN G B,WANG H N,YAO J J,et al.Three-dimensional numerical modeling of marine controlled-source electromagnetic responses in a layered anisotropic seabed using integral equation method[J].Acta Physica Sinica,2009,58(6):3848-10.(In Chinese)
[15] 殷长春,张平,蔡晶.海洋直流电阻率法各向异性正演模拟研究[J].应用地球物理,2016,13(12):279-287.YIN C C,ZHANG P,CAI J.Forward modeling of marine dc resistivity method for a layered anisotropic earth[J].Applied Geophysics,2016,13(12):279-287.(In Chinese)
[16] 沈金松,郭乃川.各向异性层状介质中视电阻率与磁场响应研究[J].地球物理学报,2008,51(5):1608-1619.SHEN J S,GUO N C.Study on the apparent resistivity and magnetic field responses of a layered earth with arbitrary anisotropy[J].Chinese Journal of Geophysics,2008,51(5):1608-1619.(In Chinese)
[17] 胡祥云,霍光谱,高锐,等.大地电磁各向异性二维模拟及实例分析[J].地球物理学报,2013,56(12):4268-4277.HU X Y,HUO G P,GAO R,et al.The magnetotelluric anisotropic two dimensional simulation and case analysis[J]Chinese Journal of Geophysics,2013,56(12):4268-4277.(In Chinese)
[18] HERREDSVELA J.,COLPAERT A.,Foss S.K.et al.Feasibility of electromagnetic methods for sub-basalt exploration[C].82nd Annual International Meeting,SEG,Expanded Abstracts,2012:1-5.
[19] ZACH J.J.,FRENKEL M.A..3d inversion-based interpretation of marine CSEM data[J].SPE Journal of Reservoir Evaluation and Engineering,2012,15(3):321-334.
[20] 罗鸣,李予国,李刚.一维垂直各向异性介质频率域海洋可控源电磁资料反演方法[J].地球物理学报,2016,59(11):4349-4359.LUO M,LI Y G,LI G.Frequency domain inversion of marine csem data in one dimensional vertically anisotropic structures[J].Chinese Journal of Geophysics,2016,59(11):4349-4359.(In Chinese)
[21] 赵宁,王绪本,秦策.基于vti各向异性介质的频率域海洋可控源电磁三维约束反演[J].地球物理学报,2017,60(5):1946-1954.ZHAO N,WANG X B,QIN C.3D frequency domain mcsem constrained inversion in vti media[J].Chinese Journal of Geophysics,2017,60(5):1946-1954.(In Chinese)
[22] BAKULIN A.,WOODWARD M.,OSYPOV K,et al.Can we distinguish tti and vti media.Meeting[J].SEG,2007:226-230.
[23] FRENKEL M.A.,FEHLER M.Seam update,phase i - rpsea update:controlled-source electromagnetic simulations[J].The Leading Edge,2012,31(9):1012-1014.
[24] YUJI MITSUHATA.2-D electromagnetic modeling by finite-element method with a dipole source and topography[J].Geophysics,2000,65(2):465-475.
[25] LI Y,KEY K.2D marine controlled-source electromagnetic modeling:Part 1 — An adaptive finite-element algorithm[J].Geophysics,2007,72(2):WA51.
[26] AMESTOY P.R.,DUFF I.S.,L’EXCELLENT JY,et al.MUMPS:A General Purpose Distributed Memory Sparse Solver.Conference paper,2001,121-130.
[27] CONSTABLE S.Ten years of marine CSEM for hydrocarbon exploration[J].Geophysics,2010,73(5):75A67.