Sedimentary Facies And Reservoir Characteristics Analysis Of Chang 2 Oil-bearing In Western Ordos Xu Xinzhuang Area

Xuxinzhuang Oil Field is located in the middle-west part of Shanbei Slope which has a great achievement in hydrocarbon exploration, reserve as well as production. However, the requirement of stale and high production is increasing with the further development of the production. The sedimentary facies and reservoir need to be deep studied. This paper has discussed the sedimentary facies, reservoir petrology characteristics, pore structure, diagenesis, physical properties and the controlling factors of this area.According to the stratigraphic lithology and electrical characteristics of Xuxinzhuang Oil Field, especially the distribution of K.9 marker bed, the Chang 2 resevoir can be divided into 3 sub-layers, which is to say, Chang 21, Chang22 and Chang23. Besides, the sedimentary sub-facies and sand body distribution can be determined by log facies marks, the lithology, the structure characteristics and the well cross-section. The results suggest that the study area is mainly delta facies which has developed delta plain sub-facies, including distributary channel and interdistributary bay micro facies. The directions of sand body distribution are mostly north-south and northeast to southwest.On the basis of the lithological characteristics, diagenesis, pore structures, heterogeneity and physical parameters analysis, it is known that the rock types of the study area is mainly greyish-green fine-grained feldspar sandstone. The proportions of quartz, feldspar and lithic are 33.7%,53.9% and 12.4% respectively. The cement include kaolinite, chlorite, ferrocalcite, calcite, and hydromica. The average porosity is 14.6%, while the average permeability is 4.34×10-3?m2 which belongs to the low porosity, ultra-low permeability reservoir. There are four types reservoir in the Chang 2 sandstone reseevoir based on the classification and evaluation of reservoir. Type ? accounts for 11.2%, type ? accounts for 67.5%, type Illaccounts for 19.1% and type ?accounts for 2.2%.The main controlling factors of the reservoir property are sedimentation and diagenesis. The sedimentation has predominated the reservoir properties. The different sedimentary microfacies represented hydrodynamic intensity which has controlled the original porosity and permeability of the reservoir by controlling the components, grain size, sorting, sand body geometry and in-layer heterogeneity of the reservoir. Diagenesis is internal control factors of the reservoir property. The pressure solution of the reservoir is weak but the compaction is moderate, at the same time, the solution of the feldspar and debris has commonly developed. The reduction porosity rate of compaction and cementation are 17.57% and 17.27% respectively, dissolution had added an average porosity of 4.36%. the primary porosity has experienced the compaction, cementation, solution process.