南海天然气水合物远景区海洋可控源电磁探测试验

为了测试我国自主设计与研发的海洋可控源电磁仪器性能及其在水合物探测中的适用性,本文从海洋可控源电磁法基本原理出发,首先根据试验海域水合物地质特征,建立简化地电模型开展理论研究,确定海洋可控源电磁试验的技术方案;利用研发的海洋可控源电磁仪器,在南海天然气水合物远景区开展探测试验,首次获得了我国深水海域的海洋可控源电磁数据.通过对采集数据进行处理与反演,获得了试验剖面的海底电性结构模型,揭示了4号测点下方存在一个50m厚的高阻层,其电阻率为25Ωm、顶部埋深为181m,为该区天然气水合物调查提供了有价值的电性参考资料.研究结果表明,自主研发的海洋可控源电磁仪器性能达到了预期的设计指标,这标志着我国海洋可控源电磁探测技术向实用化进程迈出了重要一步.

Experiment of marine controlled-source electromagnetic detection in a gas hydrate prospective region of the South China Sea

The purpose of this work is to test the performance of the marine controlled-source electromagnetic apparatus designed and developed by ourselves and its application in the detection of gas hydrates. Starting from the principles of the marine controlled source electromagnetic method (MCSEM), we established an ideal geo-electric model based on geological characteristics of hydrates in the test area. By carrying out the theoretical research of forward modeling and inversion calculation, we determined the technical scheme of marine controlled source electromagnetic testing. Then we utilized this apparatus and carried out the first marine electromagnetic detection in a gas hydrate prospective area of the South China Sea and collected the first batch of marine controlled-source electromagnetic data. Processing and inversion of the acquired data yielded subsurface electrical structure which differs obviously in vertical and lateral directions. Especially at the site 4, there exists an electrical resistivity layer with thickness of 50 m, top depth of 181 m and resistivity of 25 Ωm. The experiment provided valuable electrical information for the submarine gas hydrate research in this area. The results demonstrate that the instrument has reached the designed index, which marks an important step toward practicability of the marine controlled-source electromagnetic method.