Abstract: Qingjian district is one of the most promising succeed blocks for stable production of Zizhou gasfield in eastern Ordos Basin. Because the study area is large with only a few drilling wells, the degree of geological knowledge is relatively low and the study area is still in the early stage of development evaluation. Taking He 8 reservoir as the research object, based on a series of fine geological research work such as sedimentary analysis and reservoir evaluation in a comprehensive comparison with Sulige tight sand gasfield, effective sand bodies thickness, scale, development frequency and distribution regularities were defined. Through analysis, it is clear that effective sand bodies scattered in space with poor continuity, have a good corresponding relationship with the distributions of the favorable sedimentary facies such as channel bars. The effective sand bodies are mainly concentrated in western sand belt in plane, and are more developed in the second layers of upper and lower submembers of He 8 member vertically. Combining geological information and production testing data, “continuous effective thickness” was chosen as the main parameter for reservoir evaluation, and reservoirs were classified into 4 types: good, medium, poor and dry layer. Then, enriched area was optimized, and the study area was divided into 3 types of zones according to different development potentials. It is recommended to deploy vertical wells in enriched zone and not to apply horizontal wells under the current technical and economic situation. This study provides a reliable geological basis for the preparation of gasfield development plan, and it is also of a certain reference significance to the geological research in the gasfields with similar conditions.

Key words: Zizhou gasfield, Qingjian district, He 8 member, effective sand body, continuous effective thickness