Effect of Fracture Roughness, Shear Displacement, Fluid Type, and Proppant on the Conductivity of a Single Fracture: A Visual and Quantitative Analysis

Abstract

Summary Proppants are one of the essential parameters in fracturing design. They not only provide fracture conductivity but also prevent “healing” of fractures. Hence, the quantification of proppant-transport characteristics is highly critical in a sustainable production from hydraulically fractured wells. Previous attempts in this regard were limited to smooth (parallel) fracture surfaces to a great extent, but the roughness of fractures may control the conductivity of hydraulic fractures in the presence of proppants. This paper focuses on experimental measurements to visually and quantitatively investigate the hydraulic characteristics of rough fractures in the presence of proppants. Transparent models of the fractures of different origin rocks (granite, marble, and limestone) were prepared. Water and polymeric solutions representing typical rheological properties of hydraulic-fracturing fluids were injected through the models (joint and sheared fractures) with and without propping agents. The conductivity changes caused by proppant distribution caused by the roughness of fracture surfaces were quantified and correlated to different fractal characteristics of surface roughness. Qualitative and quantitative analyses were supported by images collected through the experiments. Proppant behaviors in joint- and shear-type fractures were observed to be different. In both cases, fracture-closure areas existed, which controlled the proppant transportation and fracture conductivity. The qualitative and quantitative data provided on the degree of conductivity change in a single fracture (in the presence and absence of propping agents) are expected to be useful in accurate performance estimation of oil/gas production from fractured systems.