A Study On Rift System In Northern Slope Of Middle Tarim Basin

Tazhong oilfield is located in the central Tarim basin, the northern slope of Tazhong uplift. The main oil and gas bearing zone is Ordovician carbonate rocks. In this paper, the characteristics and mechanism of fracture system are studied, and the controlling effect of fault on reservoir and hydrocarbon migration is defined, and then the relationship between fracture and hydrocarbon accumulation and distribution is analyzed.Fracture is the most important controlling factor in the development of the high quality reservoir of Ordovician carbonate rocks in Tazhong:(1) at the time of the event, the rock strata of the two disks are staggered, resulting in the breaking of the rock, tension crack, and the porosity and permeability of the fractured zone increased in different degrees;(2) the surface water along the fracture occur downward dissolution, forming the surface leaching limestone reservoir;(3) deep hydrothermal fluid along the fracture occurr upward migration, and of its flow carbonate rocks occur dissolution and dolomitization, form the hole and slot combination, greatly improve the reservoir physical property, accordingly improve the degree of reservoir development.Fractures are the channels of oil and gas migration, communicate with oil source and are the direction of hydrocarbon migration, but also destroy the ancient reservoir.In Tazhong, because of carbonate fractures, The high efficiency of oil gas in carbonate rock is high, which can carry on long distance migration, which makes the distribution of oil and gas large.Fracture system, Therefore, it is important to study the structure, characteristics, combination types and the relationship between fracture and hydrocarbon accumulation, which is important for the accumulation and distribution of oil and gas accumulation.Using GeoEast feature technique, the seismic data are processed prestack and poststack, and the recognition ability of the horizon and fault in seismic data is improved. Then, for different levels of fracture, respectively, the selection of attribute parameters, to extract the fracture properties, and multiple attributes selection, fusion, to achieve large, medium and small classification of the purpose of depicting fracture.Using 3D seismic data, based on the detailed interpretation of both areal and vertical directions, the structural evolution analysis, the geometry, kinematics and dynamics analysis of the fault are carried out, and the results of the three major categories of thrust, sinistral strike slip, X-pattern strike slip, and the different kinds of small faults, which can achieve a comprehensive and accurate interpretation of the Ordovician fracture.The Tazhong northern slope is divided into "four area three zones" of different types of exploration and development blocks, provide the basis for further oil and gas exploration.Because of the large thickness of the mobile sand dunes, the quality of seismic data is poor, and the accuracy and reliability of the results are greatly hindered.