Origin of petroleum in Bangladesh
Origin of petroleum in Bangladesh
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孟加拉国石油产地
DOI：
10.1306/61eedb66-173e-11d7-8645000102c1865d
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发表时间：
2002
期刊：
影响因子：
3.5
通讯作者：
A. Shamsuddin
中科院分区：
文献类型：
--
作者：
J. Curiale;G. Covington;A. Shamsuddin;J. Morelos;A. Shamsuddin
孟加拉国只钻了不到70口探井(207,000平方公里)，大部分位于东部陆上和近海地区，使其成为世界上勘探最少的国家之一。自早白垩世以来，构造发展控制了可供沉积的可容纳空间。孟加拉以北印度板块与欧亚大陆的碰撞，以东印度板块与缅甸板块的碰撞，为孟加拉东部渐新世-中新世烃源岩和中新统储集砂的发育提供了有利条件。由此形成的杰纳姆-布班博卡-比勒石油系统是迄今为止发现的最活跃的系统，在孟加拉国东部占主导地位。碳氢化合物可能也来自中新世布班组富含有机物质的页岩。仅杰纳姆-布班博卡-比勒石油系统就产生了迄今为止发现的16tcf以上的天然气，主要是在吉大港-特里普拉褶皱带的苏尔马盆地。孟加拉国还设想了其他几个石油系统。总而言之，对总资源量的最佳技术估计约为61tcf，包括已发现油田内的储量、预期油田增长和新发现的油田。除了一些地表渗漏气体和两个地下堆积中的少量细菌贡献外，孟加拉国的气体是产热的。模拟结果表明，天然气及其伴生凝析油来自至少6公里的峰值生成深度。许多天然气聚集与反凝析油有关，其成分由两个不同的源相和垂直运移的溶解/出溶效应决定。大多数凝析油具有分子特征，表明主要的富氢被子植物(开花陆地植物)对其源岩的有机质有贡献(S)。天然气中甲烷的碳同位素比值以及伴生凝析油的同位素和分子特征表明，苏尔马盆地北部的石油源相与南部的石油源相截然不同。根据地质框架和我们的盆地模型进行解释时，这些同位素和分子结果表明，在北纬24.4度以北，渐新世杰纳姆组是主要贡献者，而中新世布班组是向南的主要贡献者。
Fewer than 70 exploration wells have been drilled in Bangladesh (207,000 km2), mostly in the eastern onshore and offshore areas, making it one of the least explored countries in the world. Tectonic developments have controlled the accommodation space available for sediment deposition since the Early Cretaceous. Collision between the Indian plate and Eurasia to the north of Bangladesh and between the Indian plate and the Burma platelet on the east provided favorable conditions for development of Oligocene-Miocene source rocks and Miocene reservoir sands in eastern Bangladesh. The resulting Jenam-Bhuban Boka Bil petroleum system is the most active system identified to date and is dominant in eastern Bangladesh. Hydrocarbons likely also have been generated from the organic-rich shales of the Miocene Bhuban formation. The Jenam-Bhuban Boka Bil petroleum system alone is responsible for the generation of more than 16 tcf of gas in place discovered to date, mostly in the Surma basin of the Chittagong-Tripura fold belt. Several other petroleum systems have been postulated in Bangladesh. Together, the best technical estimate of the total resource base is about 61 tcf, including reserves within the discovered fields, anticipated field growth, and new field discoveries. With the exception of small bacterial contributions in some surface seep gases and two subsurface accumulations, the gases of Bangladesh are thermogenic. Modeling results indicate that the gases and associated condensates are sourced at peak generation depths of at least 6 km. Many of the gas accumulations are associated with retrograde condensates whose compositions are defined by two distinct source facies and by the solution/exsolution effects of vertical migration. Most of the condensates possess molecular signatures that indicate a major hydrogen-rich, angiospermous (flowering land plant) contribution to the organic matter of their source rock(s). The carbon isotope ratios of the methane in the gases and the isotopic and molecular characteristics of the associated condensates indicate a distinct source facies for petroleums of the northern Surma basin relative to those in the south. These isotopic and molecular results, when interpreted in light of the geological framework and our basin models, suggest that the Oligocene Jenam formation is the major contributor north of 24.4 degreesN and that the Miocene Bhuban formation is the major contributor to the south.