Dynamic elastic properties of coal
Dynamic elastic properties of coal
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DOI：
10.1190/1.3508874
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发表时间：
2010-11-01
期刊：
影响因子：
3.3
通讯作者：
Prasad, Manika
中科院分区：
文献类型：
--
作者：
Morcote, Anyela;Mavko, Gary;Prasad, Manika
不同煤种的实验室超声声速测量结果表明，煤的动弹性特性与煤级和有效压力有关。尽管人们对煤层作为甲烷生产的目标越来越感兴趣，沉积序列中的高丰度以及它们对地震响应的强烈影响，但关于煤的声学特性的数据很少。速度进行了测量，在核心插头平行和垂直于层压表面的围压高达40 MPa的加载和卸载循环的函数。P-和S-波速度和干体积和干剪切模量随着煤阶的增加而增加。因此，烟煤和烛煤显示出较低的速度和模量比更高等级的煤，如半无烟煤和无烟煤。干样的V（P）-V（S）关系是线性的，并涵盖了相对较宽的有效压力和煤阶。然而，有一个压力依赖于煤的弹性性质的围压低于5 MPa。这种压力敏感性与微裂纹的存在有关。最后，数据显示，在围压高于5 MPa（大多数微裂纹的闭合压力）时，煤具有固有各向异性。这种内在的各向异性在高压下可能是由于精细的层压和优选取向的显微组分。
Laboratory ultrasonic velocity measurements of different types of coal demonstrate that their dynamic elastic properties depend on coal rank and applied effective pressure. In spite of the growing interest in coal beds as targets for methane production, the high abundance in sedimentary sequences and the strong influence that they have on seismic response, little data are available on the acoustic properties of coal. Velocities were measured in core plugs parallel and perpendicular to lamination surfaces as a function of confining pressure up to 40 MPa in loading and unloading cycles. P- and S-wave velocities and dry bulk and dry shear moduli increase as coal rank increases. Thus, bituminous coal and cannel show lower velocities and moduli than higher ranked coals such as semianthracite and anthracite. The V(P)-V(S) relationship for dry samples is linear and covers a relatively wide range of effective pressures and coal ranks. However, there is a pressure dependence on the elastic properties of coal for confining pressures below 5 MPa. This pressure sensitivity is related to the presence of microcracks. Finally, the data show that coal has an intrinsic anisotropy at confining pressures above 5 MPa, the closing pressure for most of the microcracks. This intrinsic anisotropy at high pressures might be due to fine lamination and preferred orientation of the macerals.