Evaluation Of Ziniquanzi Reservoir In Sikeshu Sag In Junggar Basin

Junggar basin, which is one of the three large basins in Xinjiang, is located in the northern part of Xinjiang. The basin is surrounded by fold mountains:the west of Junggar Mountain is located in the Northwest of Junggar basin; Tianshan Mountain is located in the south of Junggar basin; Altai Mountains is located in the northeast of Junggar basin. Junggar basin is approximately in the shape of triangle, which is about130000square kilometers. The terrain of the basin is tilted and the southeast of the basin is higher than the northwest. The basin development carboniferous strata--quaternary strata. The oil and gas resources of Junggar basin is very plentiful, especially most of hydrocarbon reservoirs are found in the edge of the basin with the low degree of exploring in the hinterland of the basin. The western part of the southern margin of Junggar basin, which includes Kaindike anticline, Xihu anticline, Dushanzi anticline and Gaoquan anticline, is the study area of this paper that is focus on the research on the reservoir of Paleogene Ziniquanzi formation. Good reservoir is one of the necessary conditions of the formation of large oil and gas reservoir.Study on reservoirs is instructive to looking for oil and gas accumulation rules and the Discovery of large oil and gas reservoir. Kayindike anticline mainly developed three reservoirs:Paleogene Anjihaihe formation, Ziniquanzi formation and Jurassic Qigu formation. Oil and gas of Ziniquanzi formation is mainly distributed to kayindike anticline. Oil and gas of Ziniquanzi formation in Xihu anticline is poor. Fluorescent powder sandstone has been seen in the third section of Xi5well and oily water has been found in the second section in Ziniquanzi formation.On the basis of sedimentary petrology, reservoir geology theory, combined with the core analysis test, different kinds of sheets, conventional logging data, geological logging data, oil test data, this paper study the character of Ziniquanzi formation reservoir in Sikeshu Sag. The main content includes the relationship between petrology, lithology, pore structure, logging interpretation, diagenesis, affecting factors of reservoir and so on. For mastering the lithology, clasolite composition and structure, the character of interstitial fillings in the reservoir of Kayindike and Xihu and finding the different between Kayindike and Xihu, petrology should be discussed; then analyze the character of the pore structure of the study area, and the research has focus on the contrast of pore structure between Kayindike, Xihu and Dushanzi. In this paper, for predicting reservoir porosity and permeability, the models of physical property and logging data have been built on the basis of mathematic theory. The types and stage of diagenesis have been studied by X-ray and geochemical data and the relationship between diagenesis and pore structure has been discussed. From what has been discussed above, the main influencing factors of reservoir property have been summarized. At last, reservoirs have evaluated by classify and high quality reservoirs have been predicted.Through the study, the understanding of Sikeshu Sag mainly includes the following points:(1) The Kayindike reservoir in Ziniquanzi formation in study area is mainly silty sandstone and quartz sandstone; Xihu reservoir develops mudstone. The reservoir in Xihu is mainly composed of lithic feldspathic and feldspathic lithic sandstone and the reservoir in Kayinsike develop feldspathic quartz sandstone. The rock composition maturity of Kayindike is higher than the rock composition maturity of Xihu.(2) The pore type of Kayindike and Xihu is mainly primary pore, and there are certain quantity of intergranular dissolved pores, intragranular dissolved pores and a few fractures. The quantity of the intergranular dissolved pore in Xihu is more than the quantity of the intergranular dissolved pore in Kayinsike; the pore type of Dushanzi is mainly intergranular dissolved pore. The throats of study area have been divided into5types by analysis of typical parameters of mercury injection. Throats in Katibdik are bigger than Throats in Xihu, and the porosity and permeability of Kayindike is higher than Xihu. The pore throat types of Kayindike are mainly classified as Type II and Type III, and The pore throat types of Xihu are mainly classified as Type III and Type IV.(3) Though the study of diagenesis, Ziniquanzi formation of Sikushu is totally at the stage of middle diagenesis. Kayindike and Xihu are both at the stage of the early middle diagenesis, and Dushanzi is probably at the stage of the late middle diagenesis. Diagenesis types and the stage of diagenesis both influence the pore structure. Pore structure can be influenced by diagenesis. Different types of diagenesis have different effect:compaction and cementation can destroy the pore, on the contrary, dissolution and recrystallitation have a positive effect on pore structure.(4) The physical propertity models are established by geophysical well logging, physical propertity data. Compared with the model developed by single logging, the correlation coefficient of the model developed by multiple logging can be obviously improved. The relationship between porosity and permeability is positive correlation, so nonlinear models have been established. The correlation coefficient of the calculating permeability and experimental data is high.(5) From the study above, there are mainly three factors that can affect the quality of rervoirs in Ziniquanzi formation:sedimentary facies, pore structure and diagenesis. Braided river delta facie is the most advantage facie. The sands of the branch channel of braided river delta are advantage with high permeability. The second is the sands of underwater distributary channel of braided river and the third is the sand of the branch channel of meandering river with low permeability. The studies show that the types of pores are related to physical properties and the size of the throat can obviously influence the permeability of reservoir. With the evolution of diagenesis, porosity declined at the beginning, then raised.(6) The advantage facies of study area are braided river delta plain and meandering river delta plain. The shape of the complanate distribution of reservoirs in study area is narrow trips, and the distribution of reservoirs is in accord with sedimentary facies.