Paleozoic reservoir beds and their favorableness in Tazhong Areas of Tarim Basin, Northwest China

Tarim Basin is the largest petroleum potential in the west of China. Tazhong Areas are located in the centre of the Tarim, and have been thought to be the key region for seeking the large oil–gas fields in the Tarim. Paleozoic is presently the major oil–gas producing strata in the Tazhong Areas, and it is really important to petroleum exploration and development in the basin. Therefore, the basic characteristics of the Paleozoic reservoir beds of the Tazhong Areas were described in detail in this paper by collecting and processing plenty of existing data. Several points about reservoir bed and oil–gas accumulation, which are presently paid close attention to, were discussed based on the reservoir bed characteristics. The results showed that clastic-rock reservoir beds with high porosity and permeability are distributed in the southeastern part of the Tazhong Areas, while carbonate reservoirs with good physical properties are all along the No. 1 Fault belt. Cements (especially carbonate cement) amount is the major factor controlling physical properties of clastic rock reservoir beds, and the sedimentary environment is that controlling those of the carbonate reservoir beds. In the Tazhong Areas, the oil–gas distributions within the Carboniferous and Silurian clastic-rock reservoir beds are closely related to the physical properties; the distributions within the Ordovician carbonates have close relation to the reservoir bed type. Finally, favorable belts for petroleum exploration in the Tazhong Paleozoic strata were predicted on the basis of relationship between oil–gas distributions and reservoir bed characteristics.