【作者】 陈同俊；

【导师】 崔若飞； 刘恩儒；

【作者基本信息】 中国矿业大学 ， 地球探测与信息技术， 2009， 博士

【摘要】 根据现有研究,瓦斯突出与多种地质因素有关。其中,煤层的构造破坏程度或裂隙发育是关键因素之一。另外,煤层裂隙作为煤层气的主要存贮空间和运移通道,直接影响着煤层气的开发效率。因此,煤层构造破坏和裂隙发育程度的探测是预防煤矿瓦斯突出和优化煤层气开采的关键因素。通过对煤层P波AVO技术的研究,修正了业界对煤田AVO技术的一些习惯性认识。认为煤层——不论是厚煤层还是薄煤层,其反射P波都适合进行AVO分析。通过煤层反射P波的AVO分析,可以识别煤层的构造破坏程度,特别是可以识别出软分层构造煤。此外,通过给出的煤层P波AVO近似方程,大大提高了煤层反射P波AVO的近似精度;通过AVO的坐标代换,扩展了可用于AVO分析的P波勘探数据范围;从而使煤层高精度AVO属性反演成为可能。通过对煤层反射P波AVO的P—G交会图分析,发现如果煤层类型不同或煤层顶/底板岩性不同时,煤层反射P波AVO的P、G散点在P—G交会图上呈有规律分布。大部分煤层存在着大量的裂隙和节理,地震波在其中传播时具有各向异性。通过引入等效各向异性介质理论,获得了VTI构造煤、HTI构造煤、裂隙型HTI构造煤和ORT构造煤的弹性常数和速度各向异性,发现在多数情况下煤层的各向异性较弱。通过引入各向异性参数,定量计算了煤层的各向异性参数值,发现煤层在多数情况下满足弱各向异性假设。通过对VTI构造煤的P波AVO特性的研究,发现VTI构造煤的P、G属性明显区别于原生煤;随着VTI构造煤的构造破坏程度的增大,其在P—G交会图上呈有规律的线性移动。通过给出的VTI构造煤P波AVO近似公式,使VTI构造煤的高精度AVO属性反演成为可能。通过对HTI构造煤的方位AVO/AVAz特性的研究,发现在小入射角情况下(小于10o),其方位AVO/AVAz的方位各向异性可以忽略;随着入射角的增大,其方位各向异性的幅度增大。当HTI构造煤的顶板为砂岩时,其方位各向异性的幅度大于顶板为泥岩时的情形。对于裂隙型HTI构造煤来说,其方位AVO/AVAz特性基本和HTI构造煤一致,但其方位各向异性明显受裂隙控制。在同等裂隙密度情况下,煤层裂隙水饱和时的规范化AVAz曲线的波幅大于气饱和的情况。当裂隙间相互连通时,渗透率对裂隙气饱和煤层的方位AVO/AVAz特性没有影响;当裂隙水饱和时,随着裂隙间渗透率的增大,煤层方位AVO的P、G值减小、AVAz曲线的波幅减小。当煤层为ORT构造煤时,其方位AVO/AVAz特性完全取决于两组裂隙的相对关系。当煤层顶板是由泥岩和砂岩组成的VTI介质时,其P波方位AVO的P、G值介于泥岩顶板和砂岩顶板情况时的取值之间;其规范化AVAz曲线的波幅同样介于泥岩顶板和砂岩顶板情况时的取值之间,但更接近于泥岩顶板时的取值。最后,通过引入的物理模拟数据,研究了观测系统对裂隙各向异性解释结果的影响,并给出了P波裂隙各向异性数据的处理和解释流程。总之,通过对煤层顶/底板反射P波AVO的分析或对薄煤层反射P波AVO的分析,可以确定煤层及其顶/底板岩性;通过对构造煤的方位AVO/AVAz特性的研究,可以确定构造煤的构造破坏程度或裂隙发育情况。更多还原

【Abstract】 As recent research, CBM (Coal Bed Methane) effusion relate with several geological factors. Among those factors, the tectonic damage or cracked degree are key factors. On the other hand, as the chief storages and main migratory channels of CBG (Coal Bed Gas), cracks affect its production directly. From those two aspects, the survey of tectonic damage or cracked degree is the key factor to prevent CBM effusion and optimize CBG production.By analyzing the technique of reflected P-wave AVO on coal beds, revised the traditional viewpoint on coal field’s P-wave AVO, and considered that all coal beds, not only thick but also thin, are fitting AVO analyzing. Through the analysis of reflected P-wave AVO, tectonic damage of coal beds identified, especially soft coal detected. In addition, by introducing coal bed’s approximation of P-wave AVO, improved approximation’s precision of reflected P-wave AVO on coal bed, and by coordinate transforming, extended analyzable data range of P-wave survey. Thus making high precision’s AVO inversion of coal beds becomes feasible. Through cross-plot analyzing of P, G attributes reflected on coal beds, finds that the scatter graphs of P, G attributes are regular spread according to different coal beds and their roof/floor.Most coal beds have massive cracks and cleavages, and when seismic wave propagating in them, seismic wave will exhibit anisotropy. By the introduction of effective media theory, achieved the elastic constant and velocity anisotropic curves of VTI coal, HTI coal, cracked HTI coal and ORT coal, and discovered that most coal beds have weak anisotropy. By importing anisotropic parameters, quantitatively achieved coal beds’anisotropies, and found that most coal beds adapt to weak anisotropic theory.By analyzing the AVO characters of P-wave on VTI coals, found that their P, G attributes are differ from primary coal obviously. Along with the enlargement of tectonic damage, they assume the orderly linear migration on P, G attributes’cross plot. By giving an AVO approximation of VTI coal, made high precision AVO inversion possible. Through the studying of azimuthal AVO/AVAz on HTI coal, discovered that the azimuthal anisotropy of azimuthal AVO/AVAz almost may neglect when incidence angle is smaller (less than 10o degree); along with incidence angle increasing, its scope of azimuthal anisotropy increases. When the roof of HTI coal is sandstone, its scope of azimuthal anisotropy is bigger than the situation of mudstone roof. Regarding cracked HTI coal, its azimuthal AVO/AVAz characters are basically consistent with HTI coal; the only difference is its azimuthal anisotropy obviously controlled by cracks. At the same crack density cases, the water saturated anisotropic scope of AVAz curve is bigger than the case of gas saturated. When cracks mutually connected, the permeability almost not affects the azimuthal AVO/AVAz characters of gas saturated. When cracks water saturated, along with the permeability increasing, the attributes of P, G and fluctuate scope of AVAz curves reduce. When coal bed is ORT coal, the distribution and fluid infilling of two group cracks decide the characters of azimuthal AVO/AVAz. When coal bed’s roof is VTI medium composed with mudstone and sandstone, its P, G attributes of P-wave azimuthal AVO are situated between mudstone roof’s value and sandstone roof’s value; and its normalized AVAz scope is similarly situated between mudstone roof’s scope and sandstone roof’s scope, but it is more close to mudstone roof’s scope. Finally, through the introduction of a physical modeling, has studied the influence of survey layout on the interpretation of cracked anisotropy, and has given the flow charts of anisotropic processing and interpretation.In brief, through analyzing reflected P-wave AVO’s characters on coal roof/floor or thin coal beds, coal bed’s lithology could be determined; through studying the velocity anisotropy and azimuthal AVO/AVAz characters of tectonic coal, the degree of tectonic damage and the development of crack distribution could be confirmed too.更多还原