Diagenesis And Reservoir Evalution Of Wu-Xia Area At The Northwest Edge In Junggar Basin

The researches on reservoir of Permian, Triassic and Jurassic of Wu-Xia area are not systematic. By the theory of reservoir geology, combined with different data and experimental technique, the results show that fan delta and lacustrine sediment systems developed in Permian, alluvial fan, fan delta and lacustrine sediment systems developed in Triassic, alluvial fan, fluvial, delta and lacustrine sedimentsystems developed in Jurassic. Clastic reservoir, dolomite reservoir and volcaniclastic reservoir are the main reservoirs. The composition maturity and texture maturity of clastic reservoir are low. The main diagenesis types include compaction, cementation, metasomatism, and dissolution. Diagenetic stage of Permian is from the medium A to the late, that of Triassic is from the early B to the medium A, and that of Jurassic is from the early A to the medium A. According to quantitative calculation of diagenesis intensity, nine kinds of diagenetic facies are divided. Through their combination, different diagenetic face belts are formed on plane. Primary pore, secondary pore and fracture are the effective pores. Primary pores are decreasing whereas secondary pores and fractures are increasing downward. Physical property and mercury penetration indicate porosity and permeability of Permian reservoir are low, that of Triassic reservoir are moderate, and that of Jurassic are high.Dolomite reservoir is low porosity-low permeability fractured reservoir, and its diagenesis is mainly dolomitisation. Volcaniclastic reservoir is high porosity-low permeability vesicular reservoir, and its diagenesis is mianly packing action of vacuole and fracture. The macroscupic element that controls reservoir is tectonism. Diagenesis controls reservoir character vertically, and sedimentary facies control it on plane. Considering these controlling factors, the evalution standard of reservoir is established, and the primary formations are evaluated. The best reservoirs are faulted belts, and Wuerhe faulted belt is better than Xiazijie faulted belt. Thrusted belts are the secondary. Dolomite and volcaniclastic rocks of Fengcheng formation are also good reservoirs.