Research On Sedimentary Facies And Reservoirs Of Lishuwa District In Xia’ermen Oil Field

As a secondary depression in Nanxiang basin, Biyang sag is located between Tanghe county and Biyang county in Henan province. The research area is the contiguous area of the arctic region in the south of the Biyang sag basin and the gentle-slope region in the northeast of the basin, and the main oil-bearing zones are H2member and H3member of Hetaoyuan series. The oil-bearing layers are plenty and thin. The lithology is complex and the oil-bearing area is small. It is a complex hydrocarbon accumulation influenced by the lithology and the structure.Based on the previous researches, integrated with numerous references and combined with the problems desperate for being solved in the present field production, following the principle of single well-section-plan, with the fine analysis of drilling data, well logging data, seismic data, test data, mud logging data, laboratory test data and core observation data and so on, sub-layer sedimentary microfacies studies and depositional evolution characteristics of the research area have been done, the sedimentary model has been summed up, and according to the production requirements the second interpretation has been done about the logging data and microscope features and distribution patterns of the reservoirs have been studied.Derived from the seismic sections, the research intervals of Lishuwa is in the stage of "fill and level up" when the sediments constantly filled the basin, the formation boundaries are stable and clear, and the marker formations were developed steadily in the whole region, which are mainly the low-resistivity mud section which was developed steadily in the whole region and the sand section which was developed from the south to the north. The near-shore sub-aqueous fan in the south of the research area was much developed in H3Ⅲ-H3Ⅱ and had a small area mainly in the shape of a tongue and had short extended distances; the braided channels were single in constant directions and the oil-bearing sand bodies are dominantly siltstones at the end of the fan, mainly in the shape of potatoes and had individual hydrodynamic pressure system. In the north it had the sedimentary characteristics of normal braided rivers, and the reservoirs were made up of pebbled coarse sands, siltstones and argillaceous siltstones; and sand bodies were distributed in a large area, and the sand-bearing layers are plenty vertically, sub-aqueous distributary channels and secondary channels were dominant; it is the main reservoir of Lishuwa district.Through the core observation and the analysis of heavy minerals and lithologic combinations and so on, combined with the comprehensive research on log curve features, the conformation, the extent and the variations in thickness of sand bodies, and the seismic reflection features and son on, it has been known that Lishuwa district was deposited during the late H3Ⅳ～H3Ⅲ H3III, mainly as a deep lacustrine. H3Ⅱ was deposited when the deep lacustrine was being turned into the delta and H3I was deposited when the delta was developed widely, H2V was deposited when the area had the most concentrated lake water and the paleoclimate was the driest, H2Ⅳ-H2Ⅲ when the delta was widely developed twice. The sedimentary model of the two sedimentary systems in Lishuwa has been summed up.According to the law that acoustic travel follows Wyllie’s principle of superposition in time, the effects of fluid qualities and saturation and mud content have been considered in the porosity model. By combining Poisson’s equation with Darcy’s formula, the theoretical computed formula of permeability has been derived. What’s more, the empirical functions of pore tortuosity and pore-throat radius have been attempted to be set up, to make the permeability computation turn from the pure empirical model to the empirical-theoretical model, which not only effectively recognizes the thickness of sandstones for common sandstone reservoirs, but also effectively recognizes the sandstone reservoirs in complex glutinite strata. With the further application of oil test data, production test data and the general laws of water-oil accumulation, the interpreted oil and water layers have been corrected according to the law that oil is in higher places and water is in lower places. The accuracy of oil-water layer interpretation can be as high as90%after the comprehensive research.Through laboratory analysis, cast thin sections and SEM analysis, it has been found out that they are low-porosity and medium-permeability reservoirs from H2IV to H3III oil formation with part of which are high-permeability and low-permeability, and the pore types of reservoirs from H2IV to H3Ⅰ are dominated by (residual primary inter-particle pores) micropores and those of reservoirs from H3Ⅱ to H3Ⅲ are inter-particle (intra-granular) dissolution pores (including moldic pores).Influenced by both the sedimentary environment and diagenesis, reservoir H2-H3have different heterogeneous features both in the plan and in the vertical direction; the heterogeneity in the middle of the braided delta channels in the south was weak while it was stronger near the channel flank; the heterogeneity of H3Ⅱ-H3Ⅲ is stronger than that of H2IV-H3Ⅰ. The control of sedimentary microfacies over the reservoirs is apparent, and thickness of sand bodies and diagenesis and son on are also important influence factors of the reservoirs, but the influence of the structural setting on the reservoirs is not apparent. Integrated with many factors, the cutoff of H2-H3reservoirs and classification standards have been given and they have been divided into four groups. What’s more, it has been determined that the profitable reservoirs of the research area are mainly H2Ⅳ51-2, H3191, and H3Ⅱ61.