西藏波林盆地侏罗—白垩系海相烃源岩评价

EVALUATION OF JURASSIC-CRETACEOUS MARINE HYDROCARBON ROCKS IN THE BOLIN BASIN, SOUTHWESTERN TIBET

王立成 王成善 伍新和 李亚林 魏玉帅

Wang Licheng Wang Chengshan Wu Xinhe Li Yalin Wei Yushuai

中国地质大学(北京)地球科学与资源学院, 北京, 100083 2. 中国石油化工股份有限公司, 石油勘探开发研究院, 北京, 100083 3. 中国石油化工股份有限公司石油勘探开发研究院, 北京,100083 4. 西藏自治区地质调查研究院, 拉萨,850000

School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China 2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China 3. SINOPEC Exploration and Production Research Institute, Beijing 100083, China 4. Tibet Institutes of Geological Survey, Lhasa 850000, China

波林盆地位于青藏高原西南缘,面积约30 000 km2,是高原内勘探程度极低的海相含油气盆地之一。通过对盆地内烃源岩展布特征以及实测剖面的烃源岩有机质丰度、类型和热演化成熟度等有机地球化学参数的分析,认为该盆地存在2套主要烃源岩:上侏罗统门卡墩组黑色页岩厚达432 m,主要沉积于外陆棚环境,残余有机碳含量在0.67%~1.62%,平均1.03%,经过有机质恢复后有机碳含量在0.91%~2.40%,平均1.48%;岗巴群黑色页岩厚度56 m,为一套外陆棚沉积,残余有机碳含量在0.7%~1.08%,平均0.86%;恢复后有机碳含量在0.96%~1.60%,平均1.21%。2套烃源岩都以Ⅱ1型有机质为主,达到高—过成熟阶段,属于盆地内的好烃源岩。因此,该盆地有较丰富的油气生成的物质基础,具有较好的油气勘探前景。

The Bolin Basin,located on the southwestern margin of Tibetan Plateau,is a Mesozoic marine petroliferous basin covering an area of 30 000 km2.The basin has been received little hydrocarbon interest for its severe climate and life conditions,although it situates in the east of Tethyan realm,which is concentrated about 70% of the total world petroleum resources.Measured section and geochemical ana-lysis are combined to better understand the hydrocarbon potential.Two major source rock units have been identified: the Upper Jurassic Menkadun Formation and the Lower Cretaceous Gangba Group.Their potential source rock successions,mainly composed of dark shales during Oxfordian-Tithonian and Aptian,respectively,were deposited in outer shelf.TOC content ranges from 0.67 to 1.62 weight percent with an average value of about 1.03 weight percent for the Menkadun Formation and 0.7 to 1.08 weight percent with an average value of about 0.86 weight percent for the Gangba Group.All shale samples are composed of a mixed typeⅡ1(oil prone) kerogen.The vitrinite reflectance data and biomarker suggest that the Gangba Group is at late mature with respect to petroleum generation and the Menkadun Formation is overmature with respect to liquid hydrocarbon generation.These data indicate the shales of the units are good potential source rocks.Therefore,the good source rocks supply abundant matters for the formation of oil and gas in this area.

财政部国家油气专项“青藏高原油气资源战略选区调查与评价”项目(XQ2004-06);中国石油化工股份有限公司海相前瞻性项目(T060007ZS15);“中央高校基本科研业务费专项资金”资助

https://doi.org/10.11781/sysydz201003276