川西北天井山古隆起固体沥青地球化学特征及其地质意义

Geochemical characteristics and geological significance of solid bitumen in Tianjingshan Paleo-uplift, Northwest Sichuan

为探究川西北地区天井山古隆起固体沥青地球化学特征、成因和来源及其地质意义,采集研究区寒武系、泥盆系和二叠系20块野外露头沥青样品,通过固体沥青族组成、生物标志化学物、碳同位素等分析测试,结合构造演化史,建立研究区沥青动态演化形成模式。结果表明:天井山古隆起固体沥青是古油藏遭受严重生物降解而形成的,寒武系和泥盆系沥青来源于筇竹寺组烃源岩,二叠系沥青来源于筇竹寺组和二叠系烃源岩的混合。天井山古隆起经历大面积古油藏聚集,沥青封堵保存条件较好的翼部是古油藏的有利勘探目标。该结果为川西北地区天井山构造勘探与开发提供指导,也为类似的构造演化复杂地区沥青形成与油气演化研究提供借鉴。

In order to explore the geochemical characteristics,origin and geological significance of solid bitumen in Tianjingshan Paleo-uplift in Northwest Sichuan,20 outcrop bitumen samples of Cambrian,Devonian and Permian in this area were collected,and the experimental analysis of solid bitumen group composition,biomarkers and carbon isotope were carried out.Combined with tectonic evolution history,the dynamic evolution formation mechanism of bitumen in the study area was established.The results show that the solid bitumen in Tianjingshan Paleouplift was formed by the serious biodegradation of the paleo reservoir.The Cambrian and Devonian bitumen sourced from the source rock of the Qiongzhusi Formation,and the Permian bitumen sourced from the mixture of the Qiongzhusi Formation and the Permian source rocks.The outcrop bitumen of multi-layer system proves that the Tianjingshan Paleo-uplift experienced a large area of paleo-oil accumulation,and the favorable exploration target of paleo-oil reservoir in this block is the wing with good bitumen sealing and preservation conditions.This study provides guidance for the next exploration and development of Tianjingshan Structure in Northwest Sichuan,and also provides reference for the study of bitumen formation and oil and gas evolution in similar areas with complex tectonic evolution.