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The Tazhong paleouplift is divided into the upper and the lower structural layers, bounded by the unconformity surface at the top of the Ordovician carbonate rock. The reservoirs in the two layers from different parts vary in number, type and reserves, but the mechanism was rarely researched before. Therefore, an explanation of the mechanism will promote petroleum exploration in Tazhong paleouplift. After studying the evolution and reservoir distribution of the Tazhong paleouplift, it is concluded that the evolution in late Caledonian, late Hercynian and Himalayan periods resulted in the upper and the lower structural layers. It is also defined that in the upper structural layer, structural and stratigraphic overlap reservoirs are developed at the top and the upper part of the paleouplift, which are dominated by oil reservoirs, while for the lower structural layer, lithological reservoirs are developed in the lower part of the paleouplift, which are dominated by gas reservoirs, and more reserves are discovered in the lower structural layer than the upper. Through a comparative analysis of accumulation conditions of the upper and the lower structural layers, the mechanism of enrichment differences is clearly explained. The reservoir and seal conditions of the lower structural layer are better than those of the upper layer, which is the reason why more reservoirs have been found in the former. The differences in the carrier system types, trap types and charging periods between the upper and the lower structural layers lead to differences in the reservoir types and distribution. An accumulation model is established for the Tazhong paleouplift. For the upper structural layer, the structural reservoirs and the stratigraphic overlap reservoirs are formed at the upper part of the paleouplift, while for the lower structural layer, the weathering crust reservoirs are formed at the top, the reef-flat reservoirs are formed on the lateral margin, the karst and inside reservoirs are formed in the lower part of the paleouplift.

Basic characteristics of Ordovician carbonate reservoir beds in the Lungudong region of northeastern part of the Tarim Basin are described in detail and the reservoir-forming conditions of oil and gas are preliminarily discussed in this paper by collecting and sorting out a large amount of data. The carbonate reservoir beds are mainly developed in open-platform and platform marginal facies; the reservoir beds have large changes in and low average values of physical property; the main type is fractured reservoir beds with the fracture-porous type second. The reservoir bed development is chiefly controlled by the distribution of sedimentary facies, tectonic activity and karstification. Whereas the accumulation and distribution of hydrocarbons in the region are controlled by an advantageous structural location, a good reservoir-caprock combination and a favorable transporting system, with the distribution characterized by zones horizontally and belts vertically, the oil and gas are mainly concentrated in areas with structural uplift, densely developed fractures, and surface karst, a vertical vadose zone, and a horizontal undercurrent belt of palaeokarst.

Tazhong No. 1 gas field is a typical vug-fractured carbonate gas condensate reservoir with high heterogeneity and complex geological characteristics. This reservoir was discovered 5 years ago. There is an urgent need to study inter-well connectivity procedures for maximum oil /gas recovery. A detailed geological understanding of the reservoir is needed to gain a detailed reservoir dynamic description and determine the optimal recovery method for this oil reservoir. These are essential to having a successful operation, as well as reducing drilling uncertainties and improving the efficiency of oilfield management. An integrated static and dynamic workflow to determine connectivity is developed with the data collected from initial production stages of over 20 wells. This paper presents the concept of dynamic characterization of the vug-fracture carbonate gas condensate reservoirs, which mainly involves data processing, wellbore flowing pressure calculation, analytical well test analysis, numerical well test analysis, long-term production data history match and decline curve analysis, and performance prediction. In addition, the authors introduced history matching and pointed out the main reasons for the significant errors between actual data and simulation results. Several examples of triple medium condensate gas filed are given. Reservoir properties, such as permeability, skin factors, are determined. Reservoir volume and OGIP are estimated. These integrated dynamics results served as input data for connectivity with geological characterization. The results also show that the methodology is necessary, which can accurately identify gas reservoir parameters and decrease the non-unique. Based on the reservoir dynamic characterization, the wells network locations are optimized and good results are obtained in oil recovery.