Research On Reservoir Description Of Chang4+5-Chang6of Shenglishan Area In Ordos Basin

On the basis of the predecessors’research achievements, reservoir description study has been done about Chang4+5and Chang6reservoirs in Yanchang Formation Shenglishan District, Ordos Basin, according to the core data, logging data, well logging data and production performance information collected in Shenlishan oil field, combined with the structural sedimentary environment of Ordos Basin.The research results are as following. Chang4+5reservoir has been divided into sublayers Chang4+5shang, Chang4+51and Chang4+52, and Chang6reservoir into sublayers Chang61, Chang62, Chang63and Chang64, based on the characteristics of the Triassic Yanchang Formation like the sedimentary cycle, lithological and electrical properties and marker formation. While the whole structure is west-trending and monoclinic, in local areas of Chang4+5and Chang6reservoirs there are still many small-sized low-amplitude nose-like uplifts, the combination of which with channel sand is the profitable range for hydrocarbon accumulations. Chang4+5and Chang6reservoirs in Yanchang Formation Shenlishan District were deposited in the delta front, and subdivided into3microfacies, underwater distributary channel, river mouth bar and interdistributary bay. The sand body in the research area was largely deposited in delta front underwater distributary channel, which is the main hydrocarbon occumulation. Rock types in the study area is mainly a set of fine sandstone, siltstone and mudstone and silty mudstone and multi-layer interaction sedimentary tuff. Reservoir pore types mainly intergranular pore, followed by feldspar dissolution pore, rarely debris dissolution pore development.. Based on the study of sedimentary facies, reservoir petrological characteristics and physical properties, the microscopic distribution of the reservoirs has been studied and their classification criteria have been set up. The comprehensive evaluation about the reservoirs are made that Chang4+5and Chang6reservoirs have the characteristics of low porosity and low or ultra-low permeability with some reservoirs as tight sand. This Chang4+5, Chang6reservoir enrichment regularity is shown as: Reservoir controlled by sedimentary facies and diagenesis in the study area, on the background of monoclinic, develop multiple nose-like uplift structure formation and enrichment of high yield of oil and gas plays a very important role. Underwater distributary channel and river mouth bar is the extension of this group of high quality oil and gas reservoir, the main reservoir types in the area for lithologic reservoir. Chang4+52, Chang6, Chang63is the best oil-gas accumulation horizon in this area. Finally, according to the study area geology background, the well spacing density, try the oil and pilot production data, degree of oil field geological research, combined with reservoir distribution characteristics of the Shenglishan oil field, we calculated the geological reserves for Chang4+51, Chang4+52, Chang61, Chang63.