Distribution of shallow gas at an offshore platform site in Bohai Bay and its genetic mechanism
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摘要:
海底浅层气严重影响海底地层的结构稳定性,因此成为影响近海海洋平台安全的重要因素。基于高精度浅地层剖面及单道地震等物探调查资料,识别了渤海湾某海洋平台周边的浅层气分布状况及顶界埋深,并分析了研究区浅层气的成因。浅地层和单道地震资料解释的浅层气分布和顶界埋深具有非常好的一致性,平台周边1 km2范围内的浅层气主要分布在平台北侧及紧贴平台西南角,呈片状或条状分布,局部呈点状分布,顶界埋深在0.6~4.0 m之间。研究区内浅层气为浅层生物成气,但该区域断层发育,不排除热解成因浅层气的存在。指出浅层气体对海洋平台的影响主要表现在变形和失稳2个方面,对海洋平台采取针对性的防护措施具有现实意义。
Abstract:Submarine shallow gas has a serious impact on the structural stability of seafloor strata, so it has become an important factor affecting the safety of offshore platforms.Based on high-precision shallow stratigraphic profiles and single channel seismic data, the distribution and top buried depth of shallow gas around an offshore platform in Bohai Bay were identified, and the origin of shallow gas in the study area was analyzed.The distribution of shallow gas interpreted by shallow strata and single channel seismic data is very consistent with the top buried depth.The shallow gas in the area of 1 km2 around the platform is mainly distributed in its north side and adjacent to its southwest corner in the form of patches or strips and locally in the form of points.The burial depth of top boundary is between 0.6 m and 4.0m.The shallow gas in the study area is shallow biogenic gas, but the fault development in this area does not rule out the existence of pyrolytic shallow gas.The influence of shallow gas on offshore platform is mainly manifested in two aspects of deformation and instability.This conclusion has practical significance for taking targeted protective measures for offshore platform.
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Key words:
- Bohai Bay /
- offshore platform /
- shallow gas /
- distribution /
- genetic mechanism
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