北羌塘坳陷东缘上三叠统巴贡组海相烃源岩特征及勘探启示  

Characteristics of marine source rock of Bagong Formation and exploration significance in the eastern margin of North Qiangtang Depression,Qiangtang Basin

作　　者：宁生伟 谢渊 付小东 宋春彦[3] 刘琪 熊绍云 NING Shengwei;XIE Yuan;FU Xiaodong;SONG Chunyan;LIU Qi;XIONG Shaoyun(Tibet University;PetroChina Hangzhou Research Institute of Geology;Chengdu Geological Survey Center,China Geological Survey)

机构地区：[1]西藏大学 [2]中国石油杭州地质研究院 [3]中国地质调查局成都地质调查中心

出　　处：《海相油气地质》2024年第1期45-56,共12页Marine Origin Petroleum Geology

基　　金：中国石油“十四五”前瞻性基础性重大科技项目所属课题“羌塘盆地油气成藏、资源潜力与战略选区研究”(编号:2021DJ0802);西藏科技厅重点研发计划“基于多源信息的羌塘盆地断裂保存条件及油气勘探选区研究”(编号:XZ202101ZY0014G);西藏自治区科技重大专项“羌塘盆地新生代岩浆活动、隆升运动和地热活动对油气的影响”(编号:XZ202201ZD0004G05)联合资助。

摘　　要：羌塘盆地北羌塘坳陷晚三叠世发育了一套分布广、厚度大的黑色泥岩,对油气勘探具有重要意义。为明确北羌塘坳陷东缘巴贡组黑色泥岩的有机地球化学特征,采集了石油沟地区61块浅井岩心和64块手钻柱塞样品,开展地球化学和矿物学技术分析,对烃源岩生烃潜力、沉积环境进行了评价。结果表明:(1)巴贡组黑色泥岩TOC分布在0.06%~5.81%之间,整体为一套差―中等烃源岩,部分达到优质烃源岩标准;形成于弱氧化―弱还原环境,有机质类型为Ⅱ_(2)―Ⅲ型,以混合型有机质为主;R_(o)分布在0.95%~1.90%之间,处于成熟晚期至高成熟阶段。(2)巴贡组烃源岩有机质丰度较高,有机质类型好,成熟度适中,生烃潜力大。(3)巴贡组烃源岩与上覆雀莫错组底部砂砾岩形成“下生上储”的源储组合,为大中型油气田的形成奠定了基础,同时巴贡组也是页岩油勘探的有利层系。这套烃源岩对北羌塘坳陷东缘常规油气和非常规油气勘探均具有重要意义。The Qiangtang Basin,located in the eastern part of the Tethys domain,is the only large-scale superimposed basin in China where no industrial oil or gas fields have been discovered.Based on the new round of comprehensive research on oil and gas geology in recent years,a set of widely distributed black mudstone with large thickness(600-800m) of Bagong Formation is found being developed in the front delta-shallow water shelf during the foreland basin stage of Late Triassic in Qiangtang Basin,which is of great significance for oil and gas exploration.In order to study the organic geochemical characteristics of the black mudstone of Bagong Formation in the eastern margin of the North Qiangtang Depression,61core samples from shallow well and 64 hand-drilled plunger samples are collected to carry out geochemical and mineralogical analysis,and the source rock potential and sedimentary environment are evaluated.The results show that:(1)The black mudstone of the Bagong Formation,with TOC of0.06%-5.81%,is poor-medium source rock on the whole,and some reach the standard of high-quality.Formed in weak oxidation-weak reduction environment,the organic matter type is Ⅱ_(2)―Ⅲ,mainly belonging mixed organic matter.It is in the late mature to high mature stage with R_(o) of0.95%-1.90%.(2)The Bagong source rock has great hydrocarbon generation potential,due to high organic matter abundance,good organic matter type,and moderate maturity.(3)There developed a source-reservoir assemblage of “lower generation and upper reservoir” between the Bagong source rock and the glutenite reservoir at the bottom of the Quemocuo Formation,which lays a foundation for the formation of large and medium-size oil and gas fields.Besides,the Bagong mudstone is a favorable layer for shale oil exploration.In general,the Bagong source rock is of great significance for conventional and unconventional oil and gas exploration in the eastern margin of the North Qiangtang Depression.

关 键 词：烃源岩 有机地球化学 生烃潜力 勘探领域 巴贡组 北羌塘坳陷 

分 类 号：TE122.1[石油与天然气工程—油气勘探]