含煤地层各向异性介质有限差分数值模拟
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摘要
煤储层是一种双重孔隙介质,其孔隙由基质孔隙和裂隙组成,并具有自身独特的割理系统。传统的煤田地震勘探将煤层假设为单一的各向同性介质,没有考虑其中裂隙对煤层的影响。利用交错网格高阶有限差分算法,分别对不同厚度VTI和HTI型煤层的弹性波传播特征进行数值模拟,获得波场快照和含煤层状介质的地震模拟记录。从波场快照中可以看出,弹性波在VTI和HTI型煤层中传播存在明显差异;煤层厚度变化对波场的敏感性要强于煤层类型的变化。
Coal reservoir is a dual porous rock composed of matrix porosity and fracture with its unique cleat sys-tem.However,coal is usually assumed to be an isotropic medium in the traditional coal seismic exploration,and the impacts of fractures on seam are not taken into account.Elastic wave propagation of VTI(transversely isotropic with a vertical symmetry axis) and HTI(transversely isotropic with a horizontal symmetry axis) coal with different thicknesses were simulated by high-order finite-difference of staggered-grid respectively to obtain wave snapshots of homogeneous coal and seismic records of coal-bearing layered strata.By comparative analysis,it was found that evident differences of elastic wave propagation exists between VTI and HTI homogeneous coal,that changes in coal thickness are more sensitive to wave field than the changes in coal type from the layered seismic simulation records.
Coal reservoir is a dual porous rock composed of matrix porosity and fracture with its unique cleat sys-tem.However,coal is usually assumed to be an isotropic medium in the traditional coal seismic exploration,and the impacts of fractures on seam are not taken into account.Elastic wave propagation of VTI(transversely isotropic with a vertical symmetry axis) and HTI(transversely isotropic with a horizontal symmetry axis) coal with different thicknesses were simulated by high-order finite-difference of staggered-grid respectively to obtain wave snapshots of homogeneous coal and seismic records of coal-bearing layered strata.By comparative analysis,it was found that evident differences of elastic wave propagation exists between VTI and HTI homogeneous coal,that changes in coal thickness are more sensitive to wave field than the changes in coal type from the layered seismic simulation records.
引文
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[2]董守华.地震资料煤层横向预测与评价方法[M].徐州:中国矿业大学出版社,2004.
[3]杨德义,彭苏萍.多分量地震勘探技术的现状及进展[J].中国煤田地质,2003,15(1):51-57.
[4]石瑛,王赟,芦俊.用3CVSP资料分析含煤地层的方位各向异性[J].煤炭学报,2007,32(8):813-817.
[5]魏修成,董敏煜.非均匀各向异性介质中弹性波的传播[J].地震学报,1998,20(6):561-572.
[6]裴正林,牟永光.地震波传播数值模拟[J].地球物理学进展,2004,10(4):933-941.
[7]ALTERMAN Z,KARAL JR F C.Propagation of elastic waves in layered media by finite difference methods[J].Bull Seism Soc Am,1968,58:367-398.
[8]VIRIEUX J.P-SV wave propagation in heterogeneous media:velocity-stress finite-difference method[J].Geophysics,1986,51(4):889-901.
[9]LEVANDER A R.Fourth-order finite-difference P-SV seismo-grams[J].Geophysics,1988,53(11):1425-1136.
[10]TSINGAS C,VAFIDIS A,KANSEWICH E R.Elastic wave propagation in transversely isotropic media using finite differ-ences[J].Geophysical Prospecting,1990,38(8):933-949.
[11]THOMSEN L.Weak elastic anisotropy[J].Geophysics,1986,51(10):1954-1966.
[12]ANDREAS R.Reflection coefficients and azimuthal AVO analy-sis in anisotropic media[D].Colorado:Colorado School of Mines,1996.
[13]CHRISTOPHER J.Finite-difference elastic wave propagation in 2D heterogeneous transversely isotropic media[J].Geophysical Prospecting,1995,43(6):843-858.
[14]FRANCIS C,CHRYSOULA T.Application of the perfectly matched absorbing layer model to the linear elastodynamic problem in anisotropic heterogeneous media[J].Geophysics,2001,66(1):294-307.
[15]牟永光,裴正林.三维复杂介质地震数值模拟[M].北京:石油工业出版社,2003.
[16]韩宝平,冯启言,刘瑞新.鲍店煤矿四采区涌水规律分析[J].煤田地质与勘探,1996,24(4):35-38.
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