Modeling Of Js²₂ Gas Reservoirs In Shaximiao Formation Of Xinchang Gas Field

This paper focuses on the formation, structure, sedimentary microfacies and reservoir characteristics of Js22 gas reservoir in Shaximiao formation, Xinchang gas field, then to establish the 3D geological model of gas reservoir based on the theories of sedimentary petrology, petroleum geology, reservoir geology and development geology via using drilling, well logging, mud logging, filed experiment and dynamic development data.The sedimentary microfacies of Js22-1 and Js22-2 layers in Shaximiao formationof Xinchang gas field are delta plain, which includes four microfacies:crevasse splay, distributary channel, interdistributary bay and natural levee. Our work indicates that the source direction is northern and the distributary channels are progradation types sand bodies in Js22-1 and Js22-2 layers. One large scale distributary channel in Js22-1 layer was found along North to South direction and two large scale distributary channels in Js22-2 layer were identified along the same direction as Js22-1 layer. The distributary channels in Js22-2 were well developed when compared with that of Js22-1.The porosity and the permeability of Js22-2 layer varies from 7% to 13% and 0.08 to 0.3× 10-3?m2, respectively. In contrast, the porosity and the permeability of Js22-1 layer varies from 8% to 12% and 0.07 to 0.3×10-3?m2, respectively. These features suggest that the reservoir is low to medium porosity and ultra low permeability. The abrupt injection coefficient, variation coefficient and gradation of permeability are nearly identical between Js22-1 and Js22-2 layers, indicating the homogeneous characteristics of the inter-layers.The 3D geological modeling of the gas reservoir was established based on the analyzing of sedimentary microfacies and reservoir characteristics. The structure model was established with seismic data using Kriging interpolation method. The sedimentary microfacies model was established with deterministic method. The sand bodies model was established with sequential indicator simulation method controlled by microfacies boundary. The porosity and permeability model were established with sequential Gaussian simulation and sequential Gaussian simulation together with porosity model. The saturation model was established with the relationship between primary oil saturation and permeability model.