川西南部侏罗系油气垂向运移特征

川西南部侏罗系为一套巨厚红色碎屑岩沉积、不具备生烃能力，却相继发现一批中小型侏罗系气藏。在前人对这些气藏气源研究的基础上，通过天然气组成，岩石含烃浓度变化，以及凝析油C4－C7轻烃族组成、储层饱和烃色谱图等，研究本区上三叠统须五段生成的油气在侏罗系地层中的运移痕迹。得出：须五段源岩生成的油气，以垂直方式从下侏罗统自流井组，经中侏罗统沙溪庙组，最后运移至上侏罗统蓬莱镇组、且进入蓬莱镇组的时间较早。并认为，断层的主要作用是增加裂缝发育，改善砂体内部及砂体与砂体之间烃类的连通性，促进了烃类的垂向运移。从侏罗系油气垂向运移研究，提示了川西南部具有广阔的浅层气勘探领域。

CHARACTERISTICS OF VERTICAL HYDROCARBON MIGRATION IN THE JURASSIC IN SOUTHERN PART OF WEST SICHUAN BASIN

In the southern part of west Sichuan Basin, the Jurassic is composed of red clastic sediments with a huge thickness, having no petroleum generating potential. However, a large number of Jurassic gas reservoirs with small to medium reserves have been found. Based on the groundwork laid by previous researches on the source of these gases, a study was made on the migration traces through analyzing the natural gas composition, hydrocarbon concentrations in the rocks, light hydrocarbons (C 4-C 7) in the condensate, and chromatographic features of saturated hydrocarbons from the reservoir extracts. It is concluded that the hydrocarbons were generated in the Xu 5 source rock of the Upper Triassic, and migrated vertically, via Ziliujing Formation of the Lower Jurassic and then Shaximiao Formation of the Middle Jurassic, into Penglaizhen Formation of the Upper Jurassic. It is also suggested that the faults enhanced development of fractures and improved connectivity both within and between the sand bodies and promoted vertical hydrocarbon migration. Results of the present work reveal a prosperous domain of exploration for shallow gas reservoirs in the area under study.