Combined application of sub-bottom and single-channel seismic profiles to marine sand and gravel resource prospecting
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摘要:
海砂需求激增导致其勘查开发力度不断加大,埋藏海砂作为重要的海砂资源赋存类型,开发其的环境影响相对较小,但找砂难度相对较大。常用来勘查埋藏海砂的物探手段是单道地震测量,其优点是可以穿透砂层,而缺点是存在多解性。浅地层剖面由于难以穿透砂层,在以往的海砂勘查中未得到足够的重视。本文利用浅地层剖面“易穿透泥难穿透砂”的特性,通过其排除泥层间接探砂,再结合单道地震直接识别砂层。泥层的浅地层剖面特征为易于识别的均质透明或层状反射,砂层的单道地震特征为中强振幅连续性差的杂乱反射,将泥层的间接排除法与砂层的直接识别法相结合,形成"浅地层剖面排除泥层+单道地震识别砂层+钻孔验证"的埋藏海砂勘查方法,可有效提高找砂成功率。
Abstract:The demand for marine sand and gravel is sharply increasing, which leads to the intensification of prospecting and exploitation offshore. As an important type of marine sand and gravel resources, extraction of buried marine sand and gravel has less environmental impacts. However, the prospecting of the buried sand and gravel deposits is relatively difficult. Single-channel seismic survey is commonly used to search for buried marine sand and gravel. It is advantaged by penetrating sand, whereas disadvantaged by multiple solutions. Sub-bottom profile has not been paid enough attention in previous marine sand and gravel investigations, due to the difficulties in penetrating sand. However, sub-bottom profile is easy to penetrate mud, and can be used to exclude the mud. In this paper, we propose a method by integrating sub-bottom and single-channel seismic profiles together. Mud could be easily recognized with the clear transparent or bedding structure on the sub-bottom profile, which could help avoiding the thick mud. Sand might be recognized by the medium-strong amplitude chaotic reflection on the single-channel seismic profile, which could guide to selecting the thick sand. Based on the understanding mentioned above, the method of "exclusion of thick mud by sub-bottom profile, identification of sand by single-channel seismic profile and verification by boreholes" is suggested for prospecting of buried marine sand and gravel so as to effectively improve the success rate of prospecting.
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表 1 钻孔岩性信息
Table 1. Lithological information of borehole
钻孔编号 水深/m 分层/m 岩性 ZK1 25.1 0~4.6 泥(流塑) 4.6~8.7 泥质中粗砂 8.7~19.0 粗砂 19.0~22.1 砾质粗砂 22.1~30.0 泥(软塑) ZK2 30.5 0~6.0 泥(流塑) 6~10.6 泥质中细砂 10.6~23.1 中砂 23.1~33.5 粗砂 33.5~34.0 泥(可塑) ZK3 34.3 0~3.8 泥(流塑) 3.8~11.8 细砂 11.8~15.7 中砂 15.7~30.0 泥(软塑) ZK4 34.9 0~14.4 泥(流塑) 14.4~27.2 泥(软塑) 27.2~29.5 泥质细砂 29.5~31.0 泥(软塑) ZK5 31.9 0~2.6 泥(流塑) 2.6~3.7 泥质细砂 3.7~15.4 中砂 15.4~18.1 泥(可塑) 18.1~21.8 泥质中细砂 21.8~30.0 泥(软塑) ZK6 29.0 0~10.8 泥(流塑) 10.8~28.1 泥(软塑) 28.1~30.0 细砂 30.0~32.8 中粗砂 32.8~33.5 泥(可塑) -
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