The research is carried out on diagenetic minerals, pore types and its impact on the physical properties in Huanjiang C81reservoir of Ordos basin, which is based on reservoir physical property test, thin sections observation and scanning electron microscopy. Several minerals closely associated with reservoir physical properties are identified from diagenetic effect views. It results in that a classification is proposed for the diagenetic facies, consisting of four kinds of diagenetic facies: ferroan calcite cementation facies, hydromica/kaolinite cementation facies, chlorite coating facies and feldspar dissolution facies. The study of C81reservoir in Huanjiang region shows that this scheme is favorable to estimate low permeability reservoir, the result shows fairly good consistency with the distribution of physical property of wells.

As the reservoir heterogeneity causes that the production accumulation of gas well has the large differences among gas wells and the gas production of a few wells decline fast, the 3D gas reservoir modeling is used for the reservoir heterogeneity characterization. By the 3D gas reservoir modeling of integrating the geological facies information into the facies modeling, a reasonable model of He8 and Shan1 formation was built, which includes the structural model, the facies model, and the reservoir properties model. Based on the model analysis, the gas sandstone belt distribution lies along the direction of from north to south. The gas sandstone in the 4, 5, 6 small layers of He8 and the 8 small layer of Shan1 is better than others. The horizontal well positions were proposed in the study area with better gas sandstone in the 3D gas reservoir model.