| The gas reservoirs of Upper Paleozoic in Sulige gas field are characterized by complex features and it is diversity between different zones. In order to deeply understand gas-bearing characteristics and controlling factors, with a guide of the oil and gas accumulation theory, this paper using drilling, logging, analysis of laboratory and field production data, analyzes the differences of the Upper Paleozoic gas reservoir in Sulige gas field among different areas and different layers of source-reservoir matching relationship, reservoir diagenetic evolution and gas charging dynamics. At the same time, author analyzes the lowest boundary of gas bearing property and control mechanism of gas bearing difference, even analyzes the accumulation mechanism and exploitation characteristics of different layers and different zones. Finally, we obtain the following conclusion:The industrial reservoir property of Upper Paleozoic gas reservoirs of central region in Sulige gas field is the best, the second is western region, and eastern zone is poor. In addition, the physical properties of He8 formation are better than that of Shanl formation. He8 and Shanl formation have the largest proportion of dissolution of pore. Dissolution of central reservoir is the strongest, followed the eastern area and the western area is the weakest. The pores in reservoir are mainly micro pores, and the throat is mainly at micro-fine level.Because of compaction and cementation compaction, the physical properties of reservoir in the east, west and middle area of Sulige gas field had reached the level of density before the main accumulation period. In this period, the reservoir porosity of He8 formation and Shanl formation in the eastern area is 7.59% and 7.05%,8.06%,7.89% in middle area, and 7.95%, 7.70% in west area respectively; After the main accumulation period till now, because of the erosion of formation pressure relief, the eastern area porosity increased by about 0.6%, about 0.51% in the middle area, the western area increased by about 0.31%. The rebound degree after pressure relief is positively correlated with the degree of regional uplift and erosion.On the basis of accumulation mode of "large hydrocarbon generation, evaporative expulsion and diffuse-type charging", author established a step-charging mode of Sulige gas field in Upper Paleozoic gas reservoir. According to previous research on basin evolution, hydrocarbon generation evolution, dynamic composition characteristics of accumulation in Ordos Basin, author apllies mudstone-compaction method and idea of defining the value within upper and lower layer to analyze charging dynamic in the reservoir, and the result shows that source rock of Upper Paleozoic strata in Sulige gas filed produced superfluous pressure due to hydrocarbon-generating pressurization, and formed fluid potential difference between source rock and reservoir, effect of consumption of fluid potential by migration is the main charging dynamics, buoyancy played a secondary role; Reservoir charging dynamics had positive correlation relationship with regional hydrocarbon generation intensity, charging dynamic in eastern region is larger than that of central region, which is minimum in western region; Study shows that charging dynamic decreased gradually with the consumption of the charging effect, and the value of Shanl formation was generally larger than He8 formatioa The spatial distribution characteristics of charging dynamics show that the Upper Paleozoic gas reservoir is mainly vertical charging, and exists lateral charging in local area.According to the study results of positive correlation between gas saturation and physical properties, author found the saturation was also controlled by source-reservior configuration and charging dynamic. Reservoirs in Shanl formation which is closer to source rock than He8 formation could obtain larger charging dynamics, and reservoirs which got lagger charging-dynamic could obtain higher gas saturation easier. Therefore, reservoir in Shanl formation is closer to source, and charging-dynamic is lagger than that of He8 formation, although physical properties is pooer, the gas saturation is higher than that of He8 formation.Research analyzes property boundary of containing gas in different zone of He8 formation and Shanl formation by statistics and method of accumulation mechanism. The results showed that the boundary was controlled by charging dynamics, reservoir physical property, pore- throat structure and source-reservior configuration relationship. Containing gas propertyes has a dynamic characteristic:charging dynamic is larger, the pore throat is smaller, property boundary of containing gas is lower. The boundary in He8 formation is greater than that of Shanl formation; Under the controlling of pore-structure, porosity and permeability rendezvous relationship, the boundary is lowest in central region. Proposity of property boundary of containing gas is between 1.5%?2.5%, and permeability range is between 0.005×10-3um2?0.010.01×10-3um2 among differernt region and formation.Gas reservoir in He8 formation and Shanl formation of Sulige gas field has characteristics of "inhomogeneous density reservior, quasi-connected trap distribution, unified accumulation system", natural gas and water in layer is distributed in forms of "diffuse", and saturation is variety in different parts. This research concluded that the tight gas reservoir of He8 formation and Shanl formation has the characteristics of accumulation of "inhomogeneous and dispersion". |
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