藏东昌都盆地沉积构造演化及油气远景分析

Sedimentary-tectonic evolution and hydrocarbon potential in the Qamdo Basin, eastern Xizang

关键词:  昌都盆地  岩相古地理  沉积构造演化  石油地质条件  青藏高原

Key words:  Qamdo Basin  sedimentary facies and palaeogeography  sedimentary-tectonic evolution  petroleum geology  Qinghai-Xizang Plateau

摘要:

根据沉积充填与沉积演化分析,昌都盆地中生代为一个叠合型盆地,晚三叠世为一个陆内断陷盆地,经历了断陷期-坳陷期-萎缩期,侏罗纪为一个受东、西两侧造山带挤压而形成的山间坳陷盆地。喜山期,昌都盆地经历了强烈的改造。昌都盆地存在3套烃源岩,即阿堵拉组和夺盖拉组潟湖相泥岩和沼泽相含煤岩系、中侏罗统东大桥组深湖相泥岩和灰岩;4套储集岩,即甲丕拉组河流相碎屑岩、阿都拉和夺盖拉组滨岸相和三角洲相碎屑岩、波里拉组颗粒灰岩和白云岩。有利油气构造均形成于侏罗纪末,与三叠系的生油阶段基本吻合,可形成较好的油气成藏,其中昌都-察雅香堆为最有利油气远景区。

Abstract:

According to the analysis of sedimentary-tectonic evolution and sedimentary filling, the Qamdo basin was a superimposed basin during the Mesozoic, an intracontinental rift basin during the Late Triassic and a intermontane downwarped basin formed by the compression of the eastern and western orogenic belts during the Jurassic. The Basin went through three phases of evolution, including rifting, downwarping and collapse, and experienced a strong transformation during the Himalayan. In the Basin, there are three sets of source rocks including the lagoon mudstone and swamp coal-bearing rock series in the Adula and Duogaila Formations, deep lacustrine mudstone and limestone in the Middle Jurassic Dongdaqiao Formation, and four sets of reservoir rocks including the fluvial clastic rocks in the Jiapila Formation, littoral and delta clastic rocks in the Adula and Duogaila Formations, and grainstones and dolostones in the Bolila Formation. In the light of sedimentary-tectonic evolution and petroleum geology, the zone of Qamdo-Qamdun in Zhag'yab is delineated as the most favourable area for the future oil and gas exploration.