西藏比如盆地下白垩统烃源岩特征

比如盆地下白垩统多尼组以海陆过渡相沉积体系为主，发育典型三角洲相沉积构造。通过对残留盆地不同部位观测点数据统计、样品测试与分析，认为多尼组烃源岩累计厚度巨大，有机质类型以Ⅱ1型与Ⅲ型为主，有机质丰度较高，TOC主峰分布在0.40%~1.20%；有机质R_o主峰分布在2.00%~5.00%，处于高-过成熟演化阶段。对多尼组烃源岩热演化指标R_o偏高的原因进行探讨，初步认为特提斯构造域独特的构造演化背景下，中生界的褶皱、堆垛加厚，以及燕山期-喜马拉雅期岩浆、热液等方面作用引起的中生界区域变质作用与局部构造变质作用，是导致中生界有机质高演化及其出现演化程度地区性差异的重要因素。由此提出，青藏高原油气勘探与评价应注重喜马拉雅期构造演化对油气富集与保存的研究。

Characteristics of the Lower Cretaceous source rock in Biru Basin,Tibet

The Lower Cretaceous Duoni Formation in Biru Basin is dominated by paralic deposits with sedimentary structures of well-developed typical delta facies.Statistical data from different observation points of the residual basin,sample analyses and measurements showed that source rocks of Duoni Formation have a great accumulated thickness,dominant typeⅡ and type Ⅲ kerogens and a high abundance of organic carbon.The TOC ranges mostly from 0.40% to 1.20%,and Ro varies mainly between 2.0% and 5.0%,indicating a high to post maturity stage.Major factors that result in a higher maturity of Duoni Formation hydrocarbon source rock were preliminarily attributed to the Mesozoic regional metamorphism and local tectonic metamorphism caused by formation thickening of the Mesozoic folding,superimposition,magma intrusion and hydrothermal fluid having developed from the late Yanshanian to Himalayan stages under unique evolutionary settings of the Tethys structural domain.As one of residual basins of Tibet,Biru Basin is of Mesozoic source rocks with higher Ro values and regional differences in thermal evolution,therefore,the tectonic evolutionary history of the Himalayan stage should be regarded as a key factor controlling oil & gas accumulation and preservation conditions in Tibet Plateau.