Research On Characteristics Of Reservoir In Es4 Formation Of Zhanhua Sag

The researches on reservoir of Zhanhua Sag are not systematic. By the theory of reservoir geology, combined with different data and experimental technique, the results show that alluvial fan-fan delta and lacustrine sediment systems developed in Es4 formation.Clastic reservoir and carbonatite beach reservoir are two of the main reservoirs. The carbonatite reservoir mainly be deposited in the south area of Bonan Depression.The clastic reservoir contains conglomeratem, glutenite,sandstone and so on,and the composition maturity and texture maturity of clastic reservoir are low. The main diagenesis types of researched area include compaction, cementation, metasomatism and dissolution. Diagenetic stage of the lower part of the Es4 formation is from the medium B to the late, and that of the upper part of the Es4 formation is mainly in the medium A. According to quantitative calculation of diagenesis intensity, different kinds of diagenetic facies can be divided. Through their combination, different diagenetic face belts are formed. From the edge of sag to the interior, carbonate cementation change into mixed cementation transition.Along with the buried depth increases, compaction effect enhancement. In the depth from 3500 meters to 4000 meters developed secondary porosity and dissolition is stronger. Secondary porosity caused by dissolution developed in the fan root. Development of carbonatite beach give priority to the southern slope of Bonan Depression.Pore types include dissolution pores and biological between grains holes, grain of inner hole etc, types are rather complicated. Glutenite reservoir and carbonatite beach reservoir as two kinds of key reservoirs, the pore type of former one mainly for the diffuse and has large variation, the pore and thoat type of the latter one are middle.On the basis of reservoir classification, the evalution standard of reservoir is established, and the primary formations are evaluated.The results show that the sand group III is the most favorable sand body of reservoir in vertical direction, furthermore the lithologic reservoir of self-generation and self-storage limestone gathered mode is also favorable which developed on upper part of Es4 formation; Horizontally the favorable zones of the development of reservoir contain the distribution area of fine sand in fan end of Luojia fan, the fan delta front in northern Bonan depression, and the fan delta front of Boshen 4.