西藏伦坡拉盆地地温场特征及烃源岩热演化史

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

袁彩萍 徐思煌

YUAN Cai-ping XU Si-huang

中国地质大学资源学院, 湖北武汉 430074

China University of Geosciences, Wuhan 430074, China

西藏伦坡拉盆地是在燕山期基底上发育的拉张型老第三纪陆相盆地。形成时间晚于中国东部新生代沉积盆地.它在始新世未发生短暂抬升,渐新世求突告结束,之后长期抬升剥蚀,沉积时间短。伦坡拉盆地具有典型热盆的特点,受区域异常热流影响,地温梯度高于50℃/km;其地表温度随青藏高原隆升而大幅降低。独特的构造、沉积演化史及地温场特征,导致了盆内牛堡组二、三段烃源岩成熟快、门限浅,利于油气生成和排运。但盆地后期改造复杂,裂缝发育,勘探证实原生油气藏破坏明显,对保存大规模的油气储量不利。

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.

国家“八五”西藏地勘专项(局-85-01-18)

https://doi.org/10.11781/sysydz200002156