Oil Reservoir Description Of Chang-8₁ Reservoir Of Yanchang Formationin Huang-227 Well Block Of Ordos Basin

With an area of about 32.96 km2, Huang-227 well block, structurally belonging to the northwest of Ordos Basin, is located in Dingbian County, Shanxi Province. At present, the understanding of reservoir characteristics and properties, which is subject to Chang-81 Formation(C81) of Triassic, is not clear enough. According to the background above, making much of 89 well data of study area, this paper is base on the reservoir quality, properties and distribution of C81, focuses on 3D geological modeling, reserves calculation and evaluation of C81 reservoir. The main results are as follows:(1) Basing on the analysis of micropetrology and pore structure of reservoir, this paper has cleared that the reservoir of C81 is an extremely low porosity and extremely permeability reservoir. The lithology of reservoir is mainly feldspathic lithic sandstone, the average porosity is 8.4%, the average permeability is 0.001 ~0.28×10-3μm2.(2) Making full use of the study of temperature-pressure system, fluid properties and forming condition of oil reservoir, this paper has confirmed that the oil reservoir of C81 is a lithologic reservoir. In view of the effect of hydrocarbon source conditions, structural characteristics and deposition, oil mainly located in the sand body of C811, which is mainly part of underwater distributary channel micro-phase, braided delta front sub-facies in the longitudinal direction, and firstly gathered into nose structures.(3) With the help of Petrel software, the 3D geological model of C81 reservoir was built. In the basis of stochastic simulation methods and phased modeling principle, the reservoir geological model, which is from well-profile-plane-3D volume, contains structure, micro-phase, reservoir properties(porosity, permeability and oil saturation) model. The result shows that the the sand body has a better reservoir properties in the underwater distributary channel.(4) Conducting on volumetric method, this paper took fully into account the reservoir attributes staging during reserves calculation. The gological reserves of C81 reservoir is 464.68×104t.(5) Through carrying out reserves evaluation, this paper classified reserves of C81 reservoir into class I II and III. Among them, the four well groups were divided into class I reserves, another four for II class, and the last one for class III.