Effective medium modeling to assess gas hydrate and free-gas evident from the velocity structure in the Makran accretionary prism, offshore Pakistan
Effective medium modeling to assess gas hydrate and free-gas evident from the velocity structure in the Makran accretionary prism, offshore Pakistan
复制标题
有效的介质模型可评估巴基斯坦近海莫克兰吸积棱柱速度结构中的天然气水合物和游离气体
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
K. Sain
中科院分区：
文献类型：
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作者：
Ranjana Ghosh;K. Sain
沉积物的地震特性受孔隙流体的强烈影响。未固结海洋沉积物的刚度随着天然气水合物的存在而增加，随着天然气的存在而降低。在巴基斯坦近海的莫克兰增生楔地震剖面上观测到的一个强似海底反射层（BSR）表明在BSR上下存在天然气水合物和游离气。天然气的弹性特性在很大程度上取决于压力和温度。因此，我们首先确定在研究区域BSR深度所计算出的压力和温度条件下天然气的弹性模量。由地震数据得出的层速度通过有效介质理论来解释，该理论是自洽近似和微分有效介质理论的结合，并伴有平滑近似，用于评估天然气水合物和游离气。结果表明，在BSR上下，天然气水合物和游离气在孔隙空间中的饱和度分别为22%和2.4%。
Seismic properties of sediments are strongly influenced by pore fluids. Stiffness of unconsolidated marine sediment increases with the presence of gas hydrate and decreases with the presence of gas. A strong bottom-simulating reflector (BSR) observed on a seismic profile in the Makran accretionary prism, offshore Pakistan, indicates the presence of gas hydrate and free-gas across the BSR. Elastic properties of gas depend largely on pressure and temperature. We, therefore, first determine the elastic modulus of gas at pressure and temperature calculated at the BSR depth in the study region. The interval velocities derived from the seismic data are interpreted by the effective medium theory, which is a combination of self-consistent approximation and differential effective medium theories, together with a smoothing approximation, for assessment of gas hydrate and free-gas. The results show the saturations of gas hydrate and free-gas as 22 and 2.4% of pore space, respectively, across the BSR.