Favorable Area Prediction And Evaluation Of Yan9Reservoir In Area Of Zhen250,Zhenyuan Oilfield

This paper select yan9member, Jurassic Yan’an Formation in the Ordos Basin as research target. According to a great deal of research on the regions’s geological data and absorbing the anterior research fruit of forefathers, on the basis of core observation description, core analysis test data and well log, combined with field profiles, drill and log data,ect, applying sedimentology, petroleum geology and geophysics theories, the sedimentary system, sedimentary microfacies, sand bodies morphology and its distribution, reservoir characteristics and the distribution of yan9member Yan’an formation reservoir in Zhenyuan area were studied systematiclly. Based on above, the oil reservoirs of this region were evaluated, and provided a base for the further exploitation.The Zhen250area belongs to southwest of Shanbei Slope, and structural form is a westward monoclinic dumping, whose local structure is located in the Qingyang of nasal fold belt. Complete structural traps do not appear in the entire range of oilfiled. Yan9reservoirs are lithologic-structural reservoirs, which are mainly controlled by sedimentation, diagenesis and palaeogeomorphology. Several nose uplift, which developed on both sides of Tianhuan depression, allocated well with the Jurassic periods of sand body. Those are good point to the Jurassic reservoirs enrichment.In this paper, based on the core photos, log report and logging curve analysis, it has established the small layer isochronous correlation framework of the research area, confirmed the regional marker beds. Combined with the sedimentary cycles of the strata in the research area, single well stratigraphic division, connected wells’isochronous contrast, based on stratigraphic section correlation, it established the unified isochronous stratigraphic framework, and the Yan9formation can be divided into Yan91, Yan91, and Yan93, totally three layers.33stratigraphic correlation sections have been done,17from northeast to southwest,16from northwest to southeast. Strata distribution has certain continuity, usually15-20m. Sand body was controlled by (lithology) sedimentation facies along the sides of river, and controlled by structure along the direction of channels. Thickness of s Yan91was15-20m, of Yan92was mainly15-25m, and of Yan93was mainly15-20m.The Yan9reservoirs in Zhen250area mainly developed braid-river. It recognized channel microfacies, lateral margin microfacies, mid-channel bar microfacies and floodplain microfacies. The results showed that, the overall thickness of the Yan92distributed stably. Yan9reservoirs are mainly fine-medium feldspathic lithic sandstone. The reservoirs have low porosity and meidium permeability; the main pore type is mainly intergranular pore, then secondary solution pore, mesopore fine pore structure is the main type; the range of porosity and permeability of Yan9reservoirs is10%-14%,4-8×10-3μm2; the Yan92layer has good physical properties after comprehensively assessed, whose porosity values mainly distributed between12-14%, most permeability values higher than4×10-3μm2, peak range of8×10-3μm2, high value areas mainly distributed in zhen302-5well, zhen306-4well blocks etc, and it is the main oil-bearing layer.This paper studied the characteristics of sedimentary microfacies, sand plane distribution, reservoirs effective thickness, porosity, permeability; the target layer belongs to homogeneity and medium heterogeneous reservoirs. The sedimentary microfacies, diagenesis and the pre-Jurassic paleogeomorphological shapes affected the reservoirs of Yan91, Yan92, and Yan93of the Yan9reservoirs.Referring classification standard of reservoir of Yan’an formation of Erdos Basin, using SPSS statistical software to calculate the influence weight coefficient of single factor, Yan9reservoirs in the study area calculated score shows:the most favorable reservoir was located in Yan92layer, which was the exploration and extension in the future, and the main development measures output layer. This research adopted the volumetric method to calculate the three different kinds of the three layers; predicted geological reserves of Yan92is48.18x104t, predicted geological reserves of Yan9layers together is125.98x104t. The resources of the study area is abundant, there will be more space for development.