Characterization and Reconstruction of Rough Fractures Based on Vector Statistics

Abstract

The characteristics of fracture networks is of great significance for unconventional geo-energy exploitation such as shale oil, shale gas and geo-thermal extraction. Natural fractures and induced fractures after reservoir stimulation control the mechanical properties and fluid flow of the reservoirs. The quantitative characterization and reconstruction of rough fractures are essential for studying the fluid flow and mechanical properties of the reservoirs with complicated fracture networks. Based on vector statistics, a vector statistical method (VSM) for quantitative characterization of rough fractures is proposed and tested using 10 standard joint profiles. Furthermore, stochastic reconstruction algorithms for single rough fractures in two-dimensional (2D) and three-dimensional (3D) models are proposed. Afterwards, a morphology comparison and quantitative evaluation of single rough fractures before and after reconstruction are conducted. When the reconstruction algorithms for a single rough fracture are used, the difference in the tortuosity and different fractal dimensions before and after reconstruction are less than 5% and 2.5%, respectively, which means the reconstruction algorithms proposed herein can reconstruct rough fractures with approximate statistical characteristics and quantitative characterization parameters. Subsequently, these stochastic reconstruction algorithms for single rough fractures are further developed for 2D and 3D modeling of conventional and rough discrete fracture networks. The results indicate that the stochastic reconstruction algorithms proposed in this study have significant potential for rough discrete fracture network modeling. In addition, the merits and limitations of the proposed algorithms in modeling discrete fracture network models are discussed.

Keywords: Rough fractures, Quantitative characterization, Vector statistics, Stochastic reconstruction, Rough discrete fracture network