Thermal Evolution Of Source Rocks Of Jurassic In Washixia Sag

The Washixia sag is an exploration-prone sag in the southeast Depression of Tarim Basin.Due to the limitation of exploration and research,it lacks systematic knowledge of the Jurassic source rock in the Washixia sag.In this paper,through geochemical testing and analysis of outcrop samples and drilling core samples,the types and maturity of source rock were studied.The thermal evolution of Jurassic source rock was studied under the technical support of the BasinMod simulation software.Some understandings have been obtained to enrich the study of source rock in the Washixia sag.1.The Kangsu Formation and the Yangye Formation are the source rock formations in the Washixia sag.The relationship between the hydrogen index(HI)and the maximum peak temperature(Tmax)of the rock pyrolysis was used to determine the type of organic matter in the source rock.The vitrinite reflectance(Ro)was used to determine the maturity of the organic matter.The organic matter type of the source rock of the Yangye Formation in Dinghushan belongs to type III and has entered the mature stage.The organic matter type of the old coal mine in Jianggalesayi is in type II2-III and is in a low-mature stage.The organic matter of the source rock of the Ruocan-1 well belonging to type II1-III,it is in the stage of low maturity.The type of organic matter of the Jurassic source rock in Qiedi-1 well is Type II1-III,and the source rock is immature.2.The present heat flow in the Tarim Basin is low,with the hot state of the cold basin.The geothermal gradients and heat flow in the Southwest Depression of Tarim and the Northern Depression of Tarim are relatively low,and the geothermal gradient and heat flow in the central uplift zone are relatively high.Because of the tectonic movement of the Altyn Tagh fault zone,the southeast Depression of Tarim is relatively high in geothermal gradient and heat flow.The present geothermal gradient in the southeast Depression of Tarim is in the range of 21.2°C/km to 31.1°C/km.3.The thermal evolution of four wells in the Washixia sag were simulated.From the simulation results of four wells,the source rocks in Ruoqiang tectonic belt are more mature,and combined with the seismic interpretation profile of the structural Kangsu Formation and Yangye Formation is thick and buried deeply.It is speculated that Ruoqiang Structure Zone is a powerful exploration zone.