| We present the results of systematic micro-scale experimental investigations of multi-phase flow through fractured rock samples under a wide range of flow conditions. The results of the study have direct applications in fluid flow through fractures in conventional reservoirs and hydraulically-induced fractures in ultra-tight unconventional reservoirs. We generate high-resolution, three-dimensional maps of fluid distribution within a rough-walled fracture and its neighboring matrix using a miniature water-wet, fractured sandstone core sample. These maps along with steady-state pressure drop data are then used to shed light on the dominant flow mechanisms and preferential flow paths through the matrix and fracture domains as well as fluid transfer between them during numerous drainage and imbibition displacement cycles. Due to the topology of the fracture in the medium and the magnitude of the local capillary pressures that are established under varying flow conditions, different flow mechanisms govern the transport of the wetting phase through the fracture and matrix, i.e., fracture layer flow, fracture bulk flow, and advancement through matrix pores. The competition between these transport mechanisms is regulated by the medium as it identifies the flow path with minimum pressure drop from the inlet to the outlet of the hybrid matrix-fracture system. The resulting balance determines the magnitude of fluid transfer experienced by the neighboring matrix and ultimate recovery as a result. In the second category of the experiments, we probe two- and three-phase flow displacement processes in proppant-packed fractured shale samples under varying stress conditions. Three sets of experiments are performed to represent the fluid flow behavior through hydraulic fractures in shale oil, shale gas, and shale gas-condensate reservoirs, respectively. In each set of experiments, we study geomechanical deformation and consequent multi-phase flow factors that reduce effective hydrocarbon permeability that in turn results in early production loss in the above-mentioned unconventional reservoirs. We examine various types of proppants including regular sand, white sand, resin-coated sand, and ISP ceramic. Different packings of the proppants including multi-layer, uniform mono-layer, and non-uniform mono-layer, are also tested under severe closure stress conditions. For the first time, wettability alteration of proppant packs due to severe embedment and deposition of shale organic matter is reported at the pore scale. Significantly improved insight developed in this work can be used to design new proppants to effectively maintain hydraulic conductivity of the fractures for extended period of time. |
