四川盆地侏罗系沙溪庙组天然气地球化学特征及地质意义

四川盆地侏罗系沙溪庙组天然气具有埋藏浅、成本低、周期短、见效快等优点,受到广泛的重视,是目前低油价下效益开发的重要现实领域之一。通过对侏罗系沙溪庙组天然气组分、天然气碳同位素等地球化学实验数据的分析,揭示了川西地区侏罗系沙溪庙组天然气来自于下伏的须家河组煤系烃源岩,川中北地区沙溪庙组天然气来自于下伏侏罗系湖相烃源岩,川东北地区侏罗系沙溪庙组天然气来自于下伏的须家河组煤系烃源岩和侏罗系湖相烃源岩。结合气源分析结果、构造背景和目前盆地致密气勘探开发程度,明确了侏罗系沙溪庙组浅层致密气向川西北、川中北和川东北地区进行"深化、甩开勘探开发部署"的总体方针,其中川西地区龙门山前缘北段的梓潼凹陷,川中北地区的金华、秋林、公山庙、营山地区以及川东北大巴山前缘的五宝场、渡口河地区具备良好的成藏条件,是下一步浅层致密气的重点勘探地区。

Geochemical characteristics and geological significance of natural gas in Jurassic Shaximiao Formation,Sichuan Basin

The natural gas in Jurassic Shaximao Formation of Sichuan Basin has the advantages of shallow burial, excellent quality, low development cost, short period and quick response. As an important practical field of efficient development under low oil prices, it has attracted much attention from exploration developers for a long term. Through analyzing the natural gas geochemical experimental data such as natural gas components and natural gas carbon isotopes of the Jurassic Shaximiao Formation, it is revealed that natural gas from the Jurassic Shaximiao Formation in the western Sichuan Basin originates from coal source rocks of the underlying Xujiahe Formation. The natural gas of Shaximiao Formation in the northern part of central Sichuan Basin is sourced from the underlying Jurassic source rocks, and the natural gas of the Jurassic Shaximiao Formation in the northeast of Sichuan Basin is from coal source rocks of the underlying Xujiahe Formation and the Jurassic lake source rocks. In combination with gas source analysis results, structural background as well as the current exploration and development degree of tight gas in the basin, the general policy of "deepening and abandoning exploration and development" is clarified for the Jurassic shallow tight gas from Shaximiao Formation towards the northwestern, north-central and northeastern regions of Sichuan Basin. Of these, in the northern section of the front edge of Longmen Mountain in the western Sichuan Basin, Jinhua, Qiulin, Gongshanmiao and Yingshan in the northern part of central Sichuan Basin as well as the Wubaochang and Duduhe areas on the front edge of Dabashan in the northeastern Sichuan Basin have good accumulation conditions, which is a key exploration area of shallow tight gas.