Petrophysics and Fluid Transport in Shales and Tight Reservoirs

The development of horizontal drilling and hydraulic fracturing has enabled the extraction of hydrocarbons from fine-grained sedimentary rocks. This type of unconventional resource has gained much attention for most oil companies all over the world. Understanding petrophysics and the gas-water-rock interactions is essential in guaranteeing the effective recovery of hydrocarbons from shale and other tight reservoirs. But shales and tight rocks are commonly highly heterogeneous with behaviors tiered in multiple scales [1, 2]. Also, within the reservoir, the coexistence of micro-/ nanopores and natural/hydraulic fractures further enhances the complexity of storage and transport spaces [3, 4]. During the last decade, the development of effective experimental and numerical methods to explore the petrophysics in shale and tight reservoirs has become a top priority for the exploitation of shale and tight reservoirs. Fluid transport in such complex media cannot be easily determined with conventional techniques, which are successfully applied for reservoir rocks. At micro-/nanoscales, the interplay between fluids and the pore wall is no longer negligible. The mechanisms of diffusion, slip flow, and sorption all significantly affect the transport of geofluids [5, 6]. Moreover, such small diameter storage and transport pores/fractures enhance the effect of pore confinement on the phase behavior of fluids [7, 8]. The bubble point pressure and phase envelop of reservoir fluids are changed. The focus of this special issue is therefore placed on an improved understanding of the phase behavior of geofluids, fluid transport mechanisms, and non-Darcy effects in nanopores of shales and other tight rocks. The purpose of this special issue is to collate high-quality research articles in petrophysics and fluid transport in unconventional reservoirs. The special issue addresses the most recent advances in physical experiments and numerical simulation techniques to study the petrophysics and gas-water-rock interactions of unconventional reservoirs across broad length and time scales.