西藏羌塘盆地达卓玛地区含油白云岩的发现及其意义

白云岩作为含油气盆地最重要的储层,长期以来一直是盆地油气评价和勘探的重点。报道近期在南羌塘安多地区达卓玛地区发现的含油白云岩地质特征。白云岩出露于中侏罗世布曲组,厚度大于30m,横向延伸大于80m,岩石类型为中-粗晶白云岩,其孔隙度在5.0%~17.0%之间,渗透率在2.84×10-3~236×10-3μm2之间,属于低孔低渗至中孔低渗储层,与已发现的隆鄂尼优质白云岩相似,是盆地良好的储集层。空间上,达卓玛白云岩位于隆鄂尼-昂达尔错白云岩东部,且处于同一层位,表明白云岩在南羌塘盆地东西展布约180km。达卓玛含油白云岩的发现扩大了羌塘盆地白云岩储层和古油藏带的范围和规模,为羌塘盆地油气地质评价和勘探部署提供了新的依据。

Discovery of oil-bearing dolomite in Dazhuoma area of Qiangtang Basin and its significance

The dolomite serves as the most important reservoir which has always been the key to the evaluation and exploration of oil and gas. The oil-bearing dolomite was found recently near the Dazhuoma area, Amdo. The oil-bearing dolomite develops in the Buqu Formation of Middle Jurassic with the thickness over 30m and the length over 80m. The rocks are the medium-coarse-grain dolomite. The porosity of the samples is in the range of 5%~17% and the permeability is from 2.84×10-3μm2 to 236×10-3μm2. The dolomite belongs to the low-porosity and low-permeability to medium-porosity and low-permeability reservoir which is similar to the high quality dolomite of Longeni. The new oil-bearing dolomite found in Amdo lies in the same layer as the dolomite in the Bi-luo Co-Angdaer Co zone, from which the authors infer that the oil-bearing dolomite has an east-west distribution for about 180km and is the most important reservoir in the basin. The discovery of oil-bearing dolomite in Dazhuoma area expands the distribution and extent of dolomite reservoir, which can provide new basis for the oil exploration and disposition in Qiangtang Basin.