摘要:
天然气水合物是一种绝缘固体,与围岩电阻率差异大,具有电磁法勘探的物性基础.在青海木里天然气水合物赋存区,开展了瞬变电磁法的勘探试验研究,发现电阻率断面图上部为连续较厚高阻层,下部低阻背景之间存在不连续高阻层.根据木里天然气水合物钻井的测井资料,上部连续高阻层可以确定为冻土层,而下部不连续高阻层位于非冻土层之间,深度上与科学钻井的天然气水合物赋存层位基本对应,处于天然气水合物稳定带,因此认为瞬变电磁法探测的下部非冻土层内不连续高阻层指示了木里天然气水合物的赋存层.研究结果表明:瞬变电磁法具有探测常年冻土带深部高阻的能力,可用于天然气水合物的勘探.
Abstract:
Gas hydrate, an insulated solid with high resistivity, has the basic physical property for electromagnetic exploration. In Muli permafrost area, TEM experiments were performed where gas hydrate samples were acquired by core. In the apparent resistivity pseudo-sections of TEM line, there exist a continuous high resistivity layer in the shallow part and a discontinuous high resistivity layer in the deep part. The shallow high resistivity layer is confirmed as tundra depending on the temperature logging of gas hydrate hole in Muli permafrost. The deep high resistivity layer, which is under the tundra, lies in the gas hydrate stability zone ( GHSZ) of Muli area. Its depth corresponds to the depth of gas hydrate-bearing layer in known drill holes. According to the experiment, the preliminary conclu-sion is that transient electromagnetic method can be used in gas hydrate exploration in permafrost area based on its high resistivity de-tection capability.
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