珠江口盆地东部海域天然气水合物的成藏地质模式  

Geological models of gas hydrate formation in the eastern sea area of the Pearl River Mouth Basin

作　　者：苏丕波[1,2] 沙志彬[1,2] 常少英[3] 梁金强[1,2] 付少英[1,2] 

机构地区：[1]国土资源部广州海洋地质调查局 [2]国土资源部海底矿产资源重点实验室 [3]中国石油勘探开发研究院杭州地质研究院

出　　处：《天然气工业》2014年第6期162-168,共7页Natural Gas Industry

基　　金：国土资源部海底矿产资源重点实验室开放基金(编号:KLMMR-2013-A-23);国家高技术研究发展计划(863计划)(编号:2013AA092501);国家自然科学基金(编号:41376076)

摘　　要：珠江口盆地东部海域是南海北部天然气水合物(以下简称水合物)资源最为丰富的区域之一,为明确该区水合物的成藏地质特征,针对两种不同地质构造单元(调查A区与B区)水合物的赋存特征,分别选取典型地震剖面,结合区域地质调查资料及岩石物性、地热和地球化学等参数分析,应用盆地模拟技术,研究了该区水合物的成藏地质模式。结果表明:①调查A区中深部断裂发育,气源岩热演化程度较低,热解气源有限,而浅部生物气气源条件充足,浅部先期形成的生物气与深部通过断裂垂向运移上来的热解气混合在一起,由盆地中心向盆地边缘侧向运聚至水合物稳定域,形成以生物气为主的混合气源水合物藏;②调查B区新生代厚度较薄,沉积物有限,所生成的生物气不足以聚集成藏,水合物藏主要为来自邻近凹陷区的深部热解气通过断裂运聚至水合物稳定域内成藏;③相对而言,调查A区气源更为充足,稳定域厚度更大,运移通道更好,是未来水合物勘探更为有利的区域。Natural gas hydrate resources were found rich in the eastern sea area in the Pearl River Mouth Basin, northern South China Sea. To understand the geological features and conditions of gas hydrate pooling in this study area, we selected two typical geological tectonic units as the Survey Area A and the Survey Area B. The geological models of gas hydrate reservoirs in the A and B areas were constructed through the typical seismic image. In combination with physical, thermal and geochemical data, the match conditions of gas hydrate formation were studied by sedimentary basin simulation. The following findings were achieved. First, in the Survey Area A, faults are well developed in moderate and deep strata where the thermal evolution degree is low in gas source rocks and the pyrol ysis gas source is limited; abundant biogenic gas sourced from the shallow strata will be mixed with the pyrolysis gas migrating vertically up from deep strata through faults and will migrate laterally from the center to the margins of the basin and eventually accu mulate in a steady area, where a natural gas hydrate pool will be thus formed. Second, in the Survey Area B, the thickness in the Cenozoic Formation is small and sediments are quite limited, so the generated biogenic gas is far from enough to form a gas pool; the deep pyrolysis gas from the neighboring depressions migrates through faults to accumulate as a natural gas hydrated pool. Comparatively speaking, the Survey Area A is featured by a plenty of gas sources, greater thickness of the pooling area, and better channels for gas migration, so it is a favorable target for natural gas hydrate exploration.

关 键 词：珠江口盆地 东部海域 天然气水合物 成藏模式 盆地模拟 BSR 气源 生物气 

分 类 号：P618.13[天文地球—矿床学]