四川盆地中生代地热特征与前陆盆地构造、沉积作用

The Mesozoic thermal regime of the Sichuan Basin and the relationship between it and the structural and sedimentary action of the foreland basin evolution

沉积盆地热体制与油气资源勘探有着密切的联系。基于石油钻井的Ro数据,采用古地温梯度法恢复了四川盆地钻井的最高古地温。结果显示,四川盆地西部、川东南和川东北的钻井,顶部的剥蚀量在3700m左右,盆地中部的剥蚀量约3100m。钻井古地温梯度在13.2～24.5℃/km之间,占热流在31.2～60.1mW/m^2之间。热流最低的钻井为L1井,最高的为W28井,前者位于川西北的龙门山前陆盆地,后者位于四川盆地南部的威远隆起。古热体制受前陆盆地发展过程中的构造、沉积作用影响,龙门山、大巴山前陆盆地具有较低的热流值。

Thermal history reconstruction of the sedimentary basin is significant to the study of oil and gas exploration. The paleo-temperature profiles reconstructed based on the vitrinite reflectance data from boreholes in the Sichuan Basin using a paleo-temperature gradient method. The results show that the erosion in the top of the boreholes was about 3 700 m in the western, southeastern and northeastern Sichuan Basin,while was about 3 100 m in the central basin. The paleo-temperature gradient ranged 13.2- 24.5 ~C/km, and the paleo-heat flow ranged 31.2 ~ 60. 1 mW/m2. The minimum value occurred at the L1 borehole which located in the Longmenshan foreland basin,northwestern Sichuan Basin,while the maximal value occurred at the W28 borehole which located in the Weiyuan uplift, southern Sichuan Basin. As a result of the structural and sedimentary action of the foreland basin evolution in Mesozoic, the heat flow was low in the Longmenshan and Dabashan foreland basins.