Abstract:

The reef-shoal reservoir of the Changxing Formation in Yuanba area, Sichuan Basin, is rich in lithofacies types. Organic reef and shoal bodies are distributed discretely, and the reservoir and physical parameters are highly heterogeneous. The reservoir architecture is quite bizarre, and the distribution of water cut is complicated. Given these features, the existing modeling methods can hardly characterize the heterogeneity within the reef-shoal reservoir in a high resolution manner, and cannot meet the demand of gas reservoir development and production. Based on the researches on gas reservoirs of reef-shoal facies in terms of geology, geophysical prospecting, well logging and production performance, the study put forward the idea of geological model constrained modelling, integrating multiple information, including reservoir architecture, geology and seismic probability body. The geological model of the reservoir of organic reef and bioclast shoal facies was established by hierarchical facies control and sequential indication simulation, and the attribute model by facies control and sequential Gaussian random simulation. The models constructed through the method can finely characterize the inner architecture of the reef-shoal reservoir, the heterogeneity characteristics of its physical parameters, and the 3-D distribution of the reservoir of organic reef and bioclast shoal facies and attribute parameters, laying a solid foundation for the efficient development of gas reservoirs.

Key words: reservoir architecture, probability body-constrained, geomodeling, reef-shoal facies, Changxing Formation, Yuanba gas field, Sichuan Basin