Comprehensive Evaluation Of Triassic Chang 6₃ Reservoir In Huangling Region In Ordos Basin

The study area Huangling is located in the southeast of the Ordos basin, the Chang 6₃ oil layer in the Yanchang Formation in Triassic is the main pay bed, which has a good prospect of exploration and development. Because of the lack of study and exploration in the Chang 6₃ oil layer in the Yanchang Formation in Triassic in the study area, the ambiguous understanding of the sedimentary facies and distribution of the sand bodies, and the insufficient study of the cutoff value of the reservoir physical property, we can hardly carry out the work of exploration and development. With a fine statistical analysis of massive data, we worked out an evaluation criterion in study area which provides a good-fitting standard for reservoir classification and evaluation in this paper.With the core observation and the actual measurement of the field sections, starting with the analysis of both the sedimentary environment and sedimentary facies, combining with the well logging data and the analytical test of the cores, we finely studied the reservoir characteristics in the Chang 6₃ oil layer in study area from all aspects, respectively, as follow: reservoir petrology characteristics, diagenesis types, reservoir physical property, the pore throat structure of the reservoir rock, the heterogeneity of reservoir characteristics and the controlling factors of the beneficial reservoir distribution. Finally, based on the established reservoir evaluation criterion, we worked out a comprehensive evaluation for the reservoir in the Chang 6₃ oil layer in study area.We give the conclusion as follow:the sand bodies, which in the deep lacustrine turbidite deposition in the Chang 6₃ oil layer in Huangling area, mainly developed turbidite mid-fan, the rock types are mainly celadon fine-grained feldspar sandstone, the reservoir rocks mainly developed intergranular pores, interparticle dissolution pores and intragranular dissolved pores, which are the main reservoir space of the formation fluids. The throat types are mainly lamellar throat, curved lamellar throat and tubular throat, which have complex structures and poor connectivity. The reservoir rocks' average porosity is 8.83%, and its average permeability is 0.16×10^-3?m². The reservoir type belongs to ultra-low porosity and super-low permeability, the vertical reservoir physical property of Chang 6₃³?Chang 6₃²?Chang 6₃¹ successively get better, while the plane reservoir physical property in the north of the study area are better than its in south. The anisotropy is poor both in the Chang 6₃ oil layer and in plane in study area, and the deposition, diagenesis, pore structure and its configuration, interlayer together control the beneficial reservoir distribution in Chang 6₃.Based on the established reservoir evaluation criterion, we classified the reservoirs in Chang 6₃ into 4 classes:class ? reservoir, class ? reservoir, class ? reservoir and class ? reservoir, of which the property successively get poor. The reservoirs are mainly class ? reservoir in study area, which have the biggest area, while the areas of both class ? reservoir and class ? reservoir are small.