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.