Abstract:

In order to solve the problems of the difference in macro-heterogeneity between the southern and northern sandstone reservoirs in the southern and northern He-1 Member of Hangjinqi, Ordos Basin, and the unclear relationship with gas reservoir types, the He-1 sandstone reservoir is taken as the research object and its identification criteria for reservoirs and compartments are defined by sandstone classification. Then, the sand body combination style is establish. And according to the development characteristics of the reservoir in the study area, the ratio of reservoir thickness to formation thickness, the ratio of reservoir thickness to formation thickness, the number of barriers, and the frequency and density of barriers are selected to characterize the characteristics of macro-heterogeneity of He-1 Member. The relation between the macro-heterogeneity and gas reservoir types is discussed. The researches are conducted as follows. ①The sandstone of the He-1 Member is divided into three types. The properties of the microfacies of box-shaped core beach in the type Ⅰ reservoir is better than that of the filling facies of the toothed box channel in the type Ⅱ reservoir. ②Three sand body assemblage modes of the He-1 Member are established. The southern part is dominated by the assemblage modes of type Ⅰ and type Ⅱ sandbody, and the northern part is dominated by the assemblage modes of type Ⅲ sandbody. ③The macro-heterogeneity of the reservoir in He-1 Member is strong in the south part and weak in the north part. ④Lithological gas reservoirs are developed in the south part with the ratio of reservoir thickness to formation thickness of less than 0.3. While the ratio of reservoir thickness to formation thickness of the north-east part is greater than 0.3 with good reservoir connectivity, which is mainly used as a natural gas migration channel and conducive to the formation of structural gas reservoirs and structural-lithological composite gas reservoirs. The gas-bearing capacity of type Ⅰ reservoirs in the south is better than that in the north. The conclusion is that the macro-heterogeneity of the reservoir of He-1 Member is strong in the south part and weak in the north-east part; the macro-heterogeneity of the reservoir affects the type of gas reservoirs, making the south part to be a lithologic gas reservoir area, and the north-east part to be a structure-lithological complex gas reservoir area. Type Ⅰ reservoirs with a ratio of reservoir thickness to formation thickness of less than 0.3 in the south part are the favorable target areas for well location deployment. It points out the direction for the selection of exploration area in He-1 gas reservoir.

Key words: reservoir macro-heterogeneity, ratio of reservoir thickness to formation thickness, barrier layer, sandstone reservoir with ultra-low to low permeability, eastern Hangjinqi zone