川西北地区海相烃源岩地球化学特征、分布规律及天然气勘探潜力  

The geochemical characteristics,distribution patterns,and gas exploration potential of marine source rocks in northwest Sichuan Basin

作　　者：胡国艺[1,2] 贺飞 米敬奎 袁懿琳[1,2] 郭谨豪 Guo-yi HU;Fei HE;Jing-kui MI;Yi-lin YUAN;Jin-hao GUO(PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China;CNPC Key Laboratory of Petroleum Geochemistry,Beijing 100083,China)

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]中国石油油气地球化学重点实验室,北京100083

出　　处：《天然气地球科学》2021年第3期319-333,共15页Natural Gas Geoscience

基　　金：国家科技重大专项课题“高过成熟阶段天然气生成机理与源灶有效性评价”(编号:2016ZX05007001)资助。

摘　　要：川西北地区为近年来四川盆地天然气勘探的热点地区,但时至今日对该区海相烃源岩的地球化学特征和分布仍缺乏全面的研究。选取8条露头剖面对川西北地区下震旦统陡山沱组、上震旦统灯三段、下寒武统筇竹寺组、下志留统龙马溪组、中泥盆统、中二叠统茅口组、上二叠统龙潭组/吴家坪组和大隆组8套海相烃源岩进行了系统的有机地球化学分析,探讨了该区天然气勘探潜力。筇竹寺组优质烃源岩厚度最大,可达80 m,其次是上二叠统龙潭组/吴家坪组和大隆组,厚度可达20~30 m,其他层系优质烃源岩厚度均较薄。从有机质丰度来看,陡山沱组、筇竹寺组、龙马溪组、龙潭组/吴家坪组和大隆组总有机碳含量(TOC)大于3%的发育优质烃源岩,灯三段、中泥盆统、茅口组有机碳含量整体偏低。从下寒武统筇竹寺组至上二叠统大隆组烃源岩干酪根碳同位素值逐渐增高,陡山沱组、灯三段和筇竹寺组烃源岩δ^(13)C值小于-30.0‰,有机质类型以Ⅰ型为主,龙潭组/吴家坪组与大隆组烃源岩δ^(13)C值主要分布在-28.0‰~-26.0‰之间,有机质类型以Ⅱ2型为主,其他介于两者之间。川西北地区除广元矿山梁、朝天二叠系和朝天泥盆系的烃源岩处于成熟阶段之外,大部分地区处于过成熟阶段,主要以生干气为主。多套高丰度烃源岩的发育奠定了川西北地区海相天然气资源丰富,以筇竹寺组和上二叠统烃源岩为气源的含气系统是川西北地区未来天然气勘探的关注领域。In recent years,the natural gas exploration in the northwest of Sichuan Basin has been paid more attention.However,the systematic study on the geochemical characteristics and distribution of marine source rocks in this study area has not been done.The potential of natural gas exploration has been systematically analyzed and discussed by selecting eight outcrop profiles from the eight sets of source rocks(i.e.the Lower Sinian Doushantuo Formation,the third Member of Upper Sinian Dengying Formation,the Lower Cambrian Qiongzhusi Formation,Lower Silurian Longmaxi Formation,the Middle Devonian,the Middle Permian Maokou Formation,Upper Permian Longtan Formation/Wujiaping Formation and Upper Permian Dalong Formation).Besides,in the eight sets of source rocks,Qiongzhusi Formation is characterized by the largest thickness of high-quality source rocks,up to 80 m.The thickness of Upper Permian Longtan Formation/Wujiaping Formation and Upper Permian Dalong Formation source rocks is up to 20-30 m,whereas the others are thinner.The average contents of TOC of Doushantuo,Qiongzhusi,Longmaxi,Longtan/Wujiaping formations source rocks are over 3%,which are high-potential source rocks,while the average contents of TOC in the third Member of Upper Sinian Dengying Formation,the Middle Devonian,and the Maokou Formation are low.The carbon isotope of kerogen in source rocks gradually becomes heavier from the Qiongzhusi Formation to the Upper Permian.Theδ^(13)C values of the kerogen in Doushantuo Formation,the third Member of Upper Sinian Dengying Formation,Lower Cambrian Series Qiongzhusi Formation are less than-30‰.The organic matter types of source rocks in Doushantuo Formation,the third Member of Upper Sinian Dengying Formation,and Lower Cambrian Qiongzhusi Formation are type I.The organic matter types of source rocks in Upper Permian Longtan Formation/Wujiaping Formation and Upper Permian Dalong Formation are typeⅡ2 with theδ^(13)C values from-28.0‰to-26.0‰mainly,while others are between type I and typeⅡ2.The maturities o

关 键 词：川西北地区 海相烃源岩 有机碳 有机质类型 成熟度 勘探潜力 

分 类 号：TE122.1[石油与天然气工程—油气勘探]