缅甸若开海域深水生物气藏形成条件与富集规律  

Deep-water biogas generation and accumulation in offshore Rakhine Basin,Myanmar

作　　者：范国章 马宏霞 邵大力 丁梁波 张颖 王海强 王雪峰 蔡峥 FAN Guozhang;MA Hongxia;SHAO Dali;DING Liangbo;ZHANG Ying;WANG Haiqiang;WANG Xuefeng;CAI Zheng(Pet-roChina Hangzhou Research Institute of Geology)

机构地区：[1]中国石油杭州地质研究院 [2]Chinnery Assets Limited

出　　处：《海相油气地质》2022年第2期146-156,共11页Marine Origin Petroleum Geology

基　　金：中国石油天然气股份有限公司科学研究与技术开发项目“海洋油气勘探关键技术研究”(项目编号:2021DJ2403)资助。

摘　　要：基于地震、钻井及有限的油气藏资料,分析了缅甸若开海域深水生物气生成的有利条件以及生物气成藏特征与富集规律。研究结果表明:①若开海域地温梯度低、沉积速率大、地层升温快,为生物气快速生成提供了有利的地质条件;②若开海域具有“陆坡控源”的生物气源岩分布规律;③叠置发育的大型水道-天然堤体系为生物气成藏提供了有利的生储盖组合;④平缓褶皱带是生物气聚集成藏的有利区带;⑤上新统和下更新统深水浊积砂岩是若开海域深水生物气勘探的重要方向。Since 2004,several gas fields(Shwe,Shwe Phyu,May,Thalin etc.)have been discovered from shelf edge to deep-water(more than 1000 m)in the Rakhine Basin,northeast Bay of Bengal.The gas is likely to be biogenic based on the methane content more than 97%andδ^(13)C ranging from-70‰to-60‰.The biogenic gas was trapped in turbidity sandstones(lobes,channels,levees and sandy MTCs)of NW-SE anticlines from Lower Pleistocene to Pliocene.The reservoir quality is moderate to good with the porosity of 20%-30%and the permeability from tens of millidarcy to hundreds of millidarcy.This paper uses high-resolution seismic data covering from shelf edge to the slope and basin,well data and gas play data to analyze the biogas generation and accumulation in deep-water turbidites,in the hope of providing some experiences for the biogas exploration in offshore Rakhine and other areas with the similar depositional environment.The research reveals the following results:(1)The gas bearing sandstones are buried at depth of 1200-3000 m below the sea level,where the reservoir temperature ranges from 30℃to 90℃.This is the suitable environment for methanobacteria.Low geothermal gradient,high sediment accumulation rate and rapid temperature rise provide good conditions for biogas generation.(2)The discovered gas fields are located at the Pliocene lower slope.The thick mudstones in the lower slope can generate a large amount biogas which can migrate in short distance and accumulate,and the high sedimentation rate in the slope is also good for preservation of porosity and suitable for methanobacteria to live.(3)The stacked large-scale channel-levee systems transported rich terrestrial organic materials.The biogas generated from these organic material can migrate into adjacent channel sandstones and lobe sandstones,forming the favorable source-reservoir-cap assemblages.(4)The anticlines in the gentle folded belt can trap a large quantity of biogas.(5)The organic matter in offshore Rakhine Basin mainly derived from the terrestrial plants.The e

关 键 词：深水 浊流沉积 生物气藏 成藏规律 若开海域 缅甸 

分 类 号：TE132.1[石油与天然气工程—油气勘探]