The Parameter And Impact Of Physical Evolution Of Lowly Permeability Reservoir On Hydrocarbon And Water Distribution Of The Chang 6 Member In Xuecha Wuqi Area Of Ordos Basin

The Chang 6 Member of Yanchang Formation Upper Triassie in Xuecha Wuqi area which is located in north shaanxi slope of Ordos Basin is a typical reservoir of low porosity and low permeability. Its oil resource is rich and one of the main exploration and development layers. But the parameter of physical evolution of lowly permeable reservoir and its impact on hydrocarbon and water distribution in the Chang 6 member is lack of recognition, because the granularity of sand is fine, the heterogeneity is very strong and the distributing of oil and water is complex. The porosities during oil accumulation are reconstructed quantitatively, and then the possible change of wetting nature and its impact on accumulation was studied, so as to establish the model of oil enrichment in sandstones on low porosity and low permeability background. The results not only have important theoretical significance, but also have important reference to next exploration and development.The results of thin sections, SEM, high pressure Hg injection, X-diffract, physical analyzed, wetting testing and image analyzed were statistically analyzed, on the base of that, the physical and wetting nature of reservoir are researched. The porosity during oil accumulation was reconstructed quantitatively based on quantitative analyses upon major diagenesis. The impact of wetting nature on petroleum accumulation was ascertained by regression analysis. The oil saturation was calculated by Archie Formula. At last the model of oil enrichment on low porosity and low permeability background was established.It is showed that the oil saturation of Chang 6 Member in Xuecha Wuqi area is low and oil-water interface is not definite. The oil saturation is mainly affected by ancient porosity and wetting nature, but at the same time the ancient porosity has made a great impact on wetting nature. The Chang 6 Member was low porosity and permeability at the end early Cretaceous Epoch due to the compaction and cementation, which caused the oil migrating difficultly at that time. But because of injected oil in middle and late Jurassic the wetting changed from water wetting nature to oil wetting nature. So the migration pathway with low resistance was formed, which favorable condition was afforded to oil accumulation.