Comprehensive Evaluation Of Upper Paleozoic Reservoirs In East Ordos Basin

The east of Ordos Basin contains gas in many strata, it is covered shallow, exploration and development potential, there are a lot of exploration and development potential, however,the study area is relatively dense reservoir,and has complex microscopic pore structure, restricting cost-effective development of oil and gas, reservoir system needs to carry out research in the study area, establish a comprehensive evaluation method of suitable for the eastern basin of tight reservoirs, provide the basis for high quality reservoir geology preferred target. Described by the above, to make the study area yields a new breakthrough, on these important issues described above and the reservoir study area classification and comprehensive evaluation of favorable areas preferred, continue to deepen the study of the contents of the above studies to further expand the production of the reservoir have a very far-reaching significance.In this paper, using a variety of analytical test methods identified as cast thin, petrography, scanning electron microscopy, high pressure mercury, constant pressure mercury, gas and water relative permeability reservoirs and NMR studies, microscopic pore structure characteristics, physical characteristics, heterogeneity, and diagenetic evolution of the flow characteristics, summarizes the different layers of the study area diagenetic facies, classification and evaluation of the study area, production data were combined with high quality reservoir target preferred, inductive analysis quality reservoir formation mechanism and controlling factors.Upper Paleozoic reservoirs in the study area of rock type quartz sandstone, lithic sandstone and lithic quartz sandstone, west of the study area as a whole showed a quartz-rich eastern part of the rich features of debris; Low compositional maturity in Taiyuan and Shanxi group, high compositional maturity in Benxi group; differences in the eastern basin of quartz cathodoluminescence zoning of the obvious things, showing the deposition of provenance; main river sand structure in the study area in a box, stacked box and bell-oriented; river edge and refers to the bell-shaped main type, underwater distributary Bay Finger-oriented; funnel sand structure mainly developed in the delta front mouth bar, barrier dam.Siliceous highest levels in the study area of Shanxi, the average was3.1%, increased the role of reservoir compaction, its content was positively correlated with quartz content; erie highest levels Taiyuan rock group, with an average of8.8%; Benxi group kaolinite Stone was the highest with an average of4.9%. The main section of the mountain an intergranular porosity type solution pores, intergranular pore followed; Shan2main types of intergranular pore solution pores and intragranular dissolved pore, intergranular pore followed; Taiyuan group main types of rock porosity crumbs dissolved pore, intergranular dissolved pore followed; Benxi group is mainly intergranular porosity type solution pores, intragranular dissolved pores and micropores.Shanxi group porosity distribution range of4-8%; Taiyuan Formation porosity distribution range of6-10%; Benxi Formation porosity distribution range of6-8%, with an average porosity of Taiyuan, the largest group, was6.24%; Shan2segment average permeability highest0.578×10-3μm2, the study area is low porosity reservoir ultra-low permeability reservoirs.Shan2sand and Taiyuan group drilling rate, the probability of obtaining industrial gas flow is relatively high, the study area is the main gas exploration horizons; between the various layers of non-penetration were strong; Shan2and Taiyuan group interlayer heterogeneity strongest mountain a second, Benxi group is relatively weak.The overall structure of the pores in the study area showed a smaller pore throat radius, large pore structure changes; expulsion pressure medium, large changes in the value of the pressure, which Benxi group mean expulsion pressure lowest0.54MPa; constant velocity mercury analysis shows mountain segment presents a large throat, small pore characteristics, the basic characteristics of mercury curve is also controlled by the throat, throat Shan2big and small, medium porosity, pore controlled mainly by the characteristic curve, Taiyuan Formation and Benxi Formation samples Shan2is basically the same, with porosity curves based, has emerged as a small throat, large pore characteristics.The original porosity of the study area to restore the original porosity of about37%of the region experienced complex diagenetic processes:compaction lost a lot of the original porosity, cementation is far greater than the loss of porosity, multi-phase dissolution the role of secondary porosity will produce large study area reservoirs were greatly improved performance.Natural seepage reservoir study area is weak, mainly hydrophilic samples; irreducible water saturation averaged50.65%, isotonic saturation point average of65.6%; study area NMR spectrum showed a unimodal T2; may dynamic changes in fluid saturation range, with an average of56.41percent, Shan2overall better, movable fluid saturation, are distributed in large pores, strong flow capacity; Taiyuan and Benxi group followed; Shan1worst movable fluid saturation is low, the small pore development, seepage poor.Analysis of the study area quality reservoir formation mechanism drawn:sedimentary facies distribution and orientation of different skeletal sand microfacies macro control of the zonal distribution of reservoir quality; lithologic control of macroscopic heterogeneity of reservoir quality distribution; different acid dissolution diagenetic stage, alkaline dissolution, fracturing, and reservoir quality is the key to explain the role of the formation.