Abstract:

The depositional facies of the 3rd Member of Lingshui Formation is braided delta controlled by fluvial and tidal processes. Moreover, the main depositional microfacies of reservoir include distributary channel, subaqueous distributary channel, river mouth bar, distal bar and sheet sand, in which mouth bars reservoir properties are better than that of distributary channel and subaqueous distributary channel; meanwhile, the reservoir properties of distal bar and sheet sand are relatively poor. Furthermore, the reservoir rhythm characteristics of vertical flowing zone are dominated by channel coarsening upward and sand bars fining upward. The interlayers and intercalations in the gas field are related to the flooding surfaces of different scales. The interlayers are mainly prodelta shales which distribute widely; however, the intercalations are mainly subaqueous distributary bay shales whose development is restricted. Integrating the depositional microfacies distribution, the reservoir heterogeneity and the fault distribution, the gas field can be divided into two vast areas including six planar flowing zones. According to the depositional distribution, there are some good reservoirs in the second and third block of the south area in the gas field, but the prospect of gas bearing should be demonstrated further because those blocks are at the low parts of the gas field structure.

Key words:  Ya13-1 Gas Field, the 3rd Member of Lingshui Formation, depositional microfacies, reservoir heterogeneity, flowing zone