羌塘盆地晚三叠世岩相古地理特征与烃源岩

羌塘盆地晚三叠世古地理格局是研究其沉积演化史和油气资源评价关键基础。通过地层划分对比、沉积相分析、沉积序列等方法，结合最新的地质调查及其研究结果，对羌塘盆地晚三叠世岩相古地理环境进行恢复，并讨论了上三叠统烃源岩基本特征。羌塘盆地晚三叠世受北侧碰撞造山挤压和南侧班公湖—怒江中特提斯洋盆打开双重影响，北羌塘前陆盆地逐渐萎缩消亡，南羌塘则经历走滑作用开始接受沉积。盆地北部的可可西里造山带、东部的岛链状隆起带和中部的中央隆起带为该时期盆地内三个物源区。北部边缘、中央隆起带东部边缘和盆地的中、东部地区，形成滨岸—三角洲相沉积。盆地中西部沉积较稳定的缓坡相碳酸盐岩。南羌塘坳陷的南部，沉积了向上水体逐渐变深的浅海陆棚相沉积物。此时期碳酸盐岩缓坡相区发育的烃源岩，具有高残余有机碳，高成熟度，低残余生烃潜量等基本特征，综合评价属于中等—较好烃源岩，以生气为主。推测多格错仁地区是今后油气勘探的优选目标和首选地区。

Lithofacies Palaeogeography and Source Rock of the Late Triassic in the Qiangtang Basin

Lithofacies palaeogeography of the Late Triassic in the Qiangtang Basin was the basis for this study of the sedimentary evolutionary history and an evaluation of its hydrocarbon resources. By means of stratigraphic division and correlation, sedimentary facies analysis and sedimentary sequencing, combined with the most recent geological investigation and research data, the palaeogeographic lithofacies environment of the Late Triassic in the Qiangtang Basin was reasonably restored, and the basic characteristics of the hydrocarbon source rocks of the Late Triassic are discussed. During the Late Triassic, the Qiangtang Basin was subjected to both collisional orogenic and compression forces in the north, and the opening of the middle Tethys oceanic basin in the Bangong Lake?Nujiang River in the south. The northern Qiangtang foreland basin gradually contracted and disappeared, while the southern Qiangtang Basin began to receive sediment as a result of intracontinental rifting (subsidence). The three provenance areas in the basin during this period are the Kekexili orogenic belt in the north of the basin, the island chain uplift belt in the east, and the central uplift belt. At the northern and eastern margins of the central uplift zone and in the central and eastern parts of the basin, littoral?delta facies deposits of marginal facies were formed. Stable carbonate rocks were deposited in the central and western areas of the basin. In the southern part of the South Qiangtang Depression, shallow shelf deposits gradually deepened upward. Hydrocarbon source rocks that were developed in the gently sloping sedimentary facies zone of carbonate rocks during this period have the basic characteristics of high residual organic carbon, high maturity and low residual hydrocarbon generation potential. From a comprehensive evaluation of the medium?to?better source rocks, mainly generating gas, it was inferred that the Doggercuoren area is the preferred target area for future oil and gas exploration.