Geological Modeling for Strong Heterogeneity Fluvial Reservoir: Member 8 Permian Shihezi Formation, Su4901 Block, Sulige gas field, Ordos Basin, China

Sulige is a tight sandstone gas field in Ordos Basin, North China, whose main gas bearing interval is Upper Permian 8th member of Shihezi Formation, a braided river deposition with low porosity and permeability. Although... [ view full abstract ]

Sulige is a tight sandstone gas field in Ordos Basin, North China, whose main gas bearing interval is Upper Permian 8th member of Shihezi Formation, a braided river deposition with low porosity and permeability. Although extensive researches have been conducted on the geological modeling of fluvial facies, some problems still need to be solved on how to characterize the strong heterogeneity of both fluvial facies architecture and reservoir quality. In this paper, we propose a new geological modeling method to characterize the strong heterogeneity of fluvial reservoir of tight sandstone gas reservoir based on the comprehensive analysis of Sulige 49-01 area, which has significant meaning for achieving the goal of optimizing and adjusting development plan and providing guidelines for similar reservoirs.

The pilot area, Su4901 Block developed a series of well-developed braided river facies in Member 8, Shihezi Formation, has about 46 wells, the main frequency of 3D seismic data is 20Hz, covering an area of roughly 167km2. The object-based method algorithm is applied to establish facies model based on the vertical stacking pattern and architectural geometries of different microfacies interpreted in Datong outcrops analogs, located in the east of Ordos Basin, and geological concepts.

A series new geological modeling methods integrating subsurface and surface data is proposed as follows: (1) The object-based modeling algorithm is applied to build the reservoir architecture model. The key point of the object-based modeling algorithm is the quantitative architecture information including the superimposition styles and scale of sand bodies, which can be based on the researches of Datong outcrop analogues. (2) On the basis of architecture model, the porosity model is established applying sequential Gaussian simulation method controlled with reservoir architecture model and trended with the impedance data derived from logging constrained inversion as the second variable. (3) Finally, We can establish the permeability model. Through this geological modeling methods and integrating these models, it can be used to evaluate the strong heterogeneity of the fluvial reservoir which is crucial to the preparation of development. Testing the method of integrating static and dynamic information to establish the geological modeling, it’s confirmed that the methodology of this paper was applicable to characterization of the similar strong heterogeneity fluvial reservoirs with low permeability.