CHARACTERISTICS OF GEOTEMPERATURE FIELD AND MATURITY HISTORY OF SOURCE ROCKS IN LUNPOLA BASIN, XIZANG(TIBET)

Lunpola Basin, developed on Yensan basement, is an extensional Eogene continental basin. It started relatively later than other Cenozoic basins in eastern China, ended at the end of Oligocene Epoch, and then uplifted until present. Its deposition period was short. It also took place a short uplifting period at the end of Eocene Epoch. Lunpola Basin is a typical HOT Basin, in which geothermal gradient was higher than 50℃/km, and temperature was decreased as Qingzang plateau elevating. Special characteristics of structure, sedimentary history and geotemperature field made source rocks of Niubao formation in the basin bury shallow and mature fast. All of those are favorable for hydrocarbon generation and expulsion. But Petroleum exploration has shown that Lunpola Basin was reformed by succeeding structure and fracture and the primary reservoir was damaged. So it is unfavorable for preserving great amount reserves of oil and gas.