羌塘盆地隆鄂尼-鄂斯玛古油藏带中侏罗统布曲组岩相古地理研究

Sedimentary facies and palaeogeography of the Middle Jurassic Buqu Formation in the Longeni-Esima ancient oil reservoirs zone,Qiangtang Basin,northern Xizang

关键词:  羌塘盆地  隆鄂尼-鄂斯玛  中侏罗统布曲组  岩相古地理

Key words:  Xizang  Longeni-Esima  Middle Jurassic Buqu Formation  sedimentary facies and palaeogeography

摘要:

羌塘盆地隆鄂尼-鄂斯玛古油藏带中侏罗统布曲组含油白云岩带主要由潮坪相及潮下浅滩相颗粒灰岩和藻纹层白云岩、颗粒白云岩组成。藻纹层白云岩与颗粒灰岩组成旋回性沉积,发育藻纹层构造、鸟眼构造;含油白云岩带之间为潟湖相暗色微泥晶灰岩、泥质灰岩、介壳灰岩。采用优势相原则,横向对比分析编制隆起剥蚀区、潮坪相带、潟湖相带和潮下浅滩相带古地理展布,以及研究区生油岩与储集层及油气藏的空间分布,预测覆盖区可能存在残存油气藏分布区。

Abstract:

The Longeni-Esima ancient oil reservoirs zone is the largest ancient oil reservoirs zone in the Qiangtang Basin, northern Xizang, where the oil-bearing formations generally occur in the dolostone strata from the Middle Jurassic Buqu Formation. In the Longeni-Esima ancient oil reservoirs zone, the oil-bearing dolostones horizons in the Middle Jurassic Buqu Formation consist mainly of the tidal-flat and subtidal shoal grainstones, algal-laminated dolostones and grainy dolostones. The grainstones and algal-laminated dolostones constitute the cyclic deposits in which the sedimentary structures such as algal-laminated structure and birdeye structure are developed, and the lagoon dark grey micritic limestone, argillaceous limestone and shell limestone are sandwiched as well. In the comparative analysis on the basis of the principle of dominant facies, the authors in this paper have reconstructed the sedimentary facies and palaeogeographic map showing the distribution of uplifted erosional areas, tidal flat facies, the lagoon facies and subtidal shoal facies, and the spatial distribution of source rocks and reservoir rocks and oil-gas reservoirs, and delineated the potential areas of residual oil and gas reservoir distribution in the study area. It is very important for the evaluation of the prospects of oil and gas resources, and the future oil and gas exploration and development in the study area.