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

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...

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

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.Theδ¹³C 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 theδ¹³C values from-28.0‰to-26.0‰mainly,while others are between type I and typeⅡ2.The maturities of source rocks in most areas are in the over mature stage,which are mainly in the thermal stage of dry gas,but Permian source rocks in Kuangshanliang section of Guangyuan,Chaotian and Devonian source rock in Chaotian are in the mature stage.The development of eight sets of high abundance source rocks has provided the rich marine natural gas resources in northwest Sichuan Basin.Therefore,the natural gas exploration targets sourced from the Qiongzhusi Formation and Upper Permian source rocks are favorable in the future.