孟加拉湾东北部上新统深水生物气成藏系统  

Pliocene deepwater biogas accumulation system in the northeastern Bay of Bengal

作　　者：鲁银涛 范国章 冉伟民 栾锡武 邵大力 马宏霞 许小勇 王红平 徐宁 刘忻蕾 杨芸 LU Yintao;FAN Guozhang;RAN Weimin;LUAN Xiwu;SHAO Dali;MA Hongxia;XU Xiaoyong;WANG Hongping;XU Ning;LIU Xinlei;YANG Yun(PetroChina Hangzhou Research Institute of Geology,Hangzhou,Zhejiang 310023,China;Qingdao Institute of Marine Geology,China Geological Survey,Qingdao,Shandong 266071,China;School of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266530,China;China National Oil and Gas Development and Exploration Company,Beijing 100031,China;North China Institute of Science and Technology,Langfang,Hebei 065201,China;Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou,Zhejiang 310012,China)

机构地区：[1]中国石油杭州地质研究院 [2]中国地质调查局青岛海洋地质研究所 [3]山东科技大学地球科学与工程学院 [4]中国石油海外勘探开发公司 [5]华北科技学院 [6]自然资源部第二海洋研究所

出　　处：《天然气工业》2022年第7期7-16,共10页Natural Gas Industry

基　　金：国家自然科学基金项目“孟加拉湾东北部深水沉积体系发育特征与生物气成藏规律研究”(编号:42076219);“东印度洋Roo海隆早期俯冲在巽他弧后东爪哇盆地的构造变形记录”(编号:42006067);“孟加拉湾东北部沉积过程与特提斯东段构造变形耦合关系”(编号:92055211)。

摘　　要：孟加拉湾东北部上新统的深水沉积砂岩中蕴藏着丰富的生物气资源,已成为该地区油气勘探的重要新目标。为进一步明确该区深水生物气的勘探前景,综合利用钻井、地震和地球化学分析等资料,对深水沉积体系平面展布样式和内部结构模式进行了研究,明确了深水重力流沉积体系与油气成藏的密切联系,以及上新统生物气成藏地质条件,探讨了生物气成藏主控因素和成藏系统。研究结果表明:①孟加拉湾东北部低地温梯度及上新世大规模发育的深水沉积体系为生物气的成藏创造了条件,低地温梯度背景拓宽了生物气生成的深度范围;②上新世高速堆积的大型深水沉积体系不仅有利于富含草本植物的有机质远距离搬运,也有利于有机质快速保存,为甲烷菌生存提供了物质基础;③厚层泥岩夹局部层段发育砂岩(“泥包砂”)的沉积结构有利于孟加拉扇发育自生自储自封堵的“独立”生物气藏,储盖组合包括水道砂岩储层—水道充填/深海泥岩盖层、天然堤砂岩储层—天然堤/深海泥岩盖层、朵叶体砂岩储层—天然堤/深海泥岩盖层、块体搬运沉积砂岩储层—天然堤/深海泥岩盖层等4种类型;④宽缓的背斜构造提高了富砂质结构单元中生物气的聚集程度。结论认为,基于孟加拉扇平缓构造背景,识别评价具有一定规模的有效圈闭是该区域生物气勘探成功的关键。研究成果不仅有助于丰富生物气成藏地质理论,同时对类似地区生物气勘探也具有重要借鉴意义。There is abundant biogas in the Pliocene deepwater sandstone deposits in the northeastern Bay of Bengal,which has become an important target of oil and gas exploration in this area.In order to further clarify the exploration prospect of deepwater biogas in this area,this paper studies the plan distribution style and internal structure pattern of deepwater depositional systems by using the data of drilling,seismic and geochemical analysis comprehensively.The close relationship between deepwater gravity flow depositional systems and hydrocarbon accumulation and the geological conditions of biogas accumulation in Pliocene are clarified.In addition,the main controlling factors and biogas accumulation systems are discussed.And the following research results are obtained.First,the low geothermal gradient in the northeastern Bay of Bengal and the extensively developed deepwater depositional system in Pliocene provide favorable conditions for biogas accumulation,and the low geothermal gradient background extends the depth range of biogas generation.Second,the large deepwater depositional system which accumulated at a high speed in Pliocene is not only conducive to the long-distance transportation of herb-rich organic matters,but also to the rapid preservation of organic matters,which provides a material basis for the survival of methanobacteria.Third,the sedimentary structure of thick mudstone with interbedded local sandstone('sandstone in mudstone')is conducive to the development of"independent"biogas reservoirs with source rocks,reservoirs and caprocks in the same layer in the Bengal Fan.The reservoir-caprock assemblages are classified into four types,including channel sandstone reservoir-channel filling/deep sea mudstone caprocks,levee sandstone reservoir-levee/deep sea mudstone reservoirs,lobe sandstone reservoir-levee/deep sea mudstone caprocks,and massive transport complex(MTC)sandstone reservoir-levee/deep sea mudstone caprocks.Fourth,the wide and gentle anticlinal structure increases the accumulation degree of bi

关 键 词：孟加拉湾东北部 上新统 深水生物气 深水沉积 成藏主控因素 成藏模式 勘探方向 

分 类 号：P618.13[天文地球—矿床学]