Abstract: Many problems are encountered during the development of tight gas. Most of them are due to the reservoir heterogeneity. The authors present a novel methodology of flow unit definition in tight gas reservoir aimed to improve the reservoir description. Based on the definition of flow unit and its geological meanings, and combined with the qualitative and quantitative analysis of the cored wells, four parameters-porosity, permeability, FZI and Winland r35 are integrated into the classification of flow units. Further, the flow barriers and connected sand bodies have been recognized by means of method of reservoir hierarchy analysis and standard of profitable gas in tight gas reservoir. And by use of cluster and discriminant analyses, a quantitative mode of flow unit definition in uncored wells has been developed, and also, three types of flow units have been recognized. Finally, the 3D geologic model of flow unit is set up using sequential indicator stochastic modeling. The model not only depicts the reservoir heterogeneity more accurately, but also provides a more useful guidance to the development of tight gas. The development practice of tight gas has proved that the flow unit A is of good reservoir quality, and hence of the best development effect, while flow unit C is the bad one. The flow unit B takes second place but has more potential than the other two.

Key words: tight sand gas, reservoir, flow unit, stochastic modeling