The Present Geothermal Field Characteristics Of The Chuxiong Basin Analysis And Hydrocarbon Source Rock Thermal Evolution History Of Recovery,

Chuxiong Basin is a reformed basin, which formed during Mesozoic-Cenozoic periods in south China and has good petroleum geological condition. Chuxiong Basin Sed-imentates three stratums including marine facies, terrestrial facies and both of them since late Trias. Due to strong post-sedimentary alternation and structural deformation, the basin has high thermal evolution degree and it is very difficult to recover the thermal evolutional history of Chuxiong Basin.By principles of integrated, dynamic and comprehensive basin analytic methods, the further research on the characteristics of present geothermal field, the recovery of the thermal evolutional and the history of oil-gas reservoirs generation were studied in Chuxiong Basin using geological, mathematical, geophysical and geochemical methods.By analyzing the characteristics of present geothermal in Chuxiong Basin, result shows that present geothermal gradient is low as a whole and ranges from 1.98 to 2.63℃/100m, the thermal gradients in the east are higher than that in the west, which are consistent with the change of crust thickness. The thermal flux of Chuxiong Basin distributes from 70 to 75 mW/m2, a rather higher thermal basin, which show that tectonic movement is active in deep stratum. Chuxiong Basin is located in Dianzhong depression and it is a middle-temperature basin.By analysis of apatite fission track, results show that Xiangyun region reaches it's highest paleogeothermal before 31.2-55.5Ma, namely mid-Paleogene period even more earlier ; In the mainbody of Chuxiong basin, such as Wulong 1, Sazhi, Yipinglang, the highest paleogeothermal was formed before 20.0 - 38.1Ma.The thermal evolutional degree is high caused by not only sedimentary process but also thermal event that happened 20.0Ma ago, the latter may be the main factor.The result of modeling thermal evolutional history shows that paleogeothermal gradient was low after sedimentating in Triassic period and changed from 2.2 to 2.5℃/100m.Geothermal was warming up from Triassic period to early Paleogene period, and the highest thermal evolution degree was formed in mid-Paleogene period. Thermal evolutional degree of Hydrocarbon rocks in the west and south is higher than that in theeast and north in Chuxiong Basin. Thermal evolutional degree of Hydrocarbon rocks is increasing with age and sedimentary depth.Through the methods including dating of illite and the homogenization temperatures of fluid inclusion combining with modeling thermal evolutional history and burial history, the forming time of oil-gas reservoirs are determined in Chuxiong Basin. Results show that the forming time of oil-gas reservoirs has two stages: The first is in the Cretaceous period and.the second is from late Cretaceous period to Paleogene period. Since Neogene period, oil-gas reservoirs was readjusted and destroyed due to tectogenesis. The forming time of oil-gas reservoirs of upper-Triassic hydrocarbon rocks is mostly in Paleogene period in Yunlong Depression, west Chuxiong Basin.