Introduction: energy and the subsurface

Abstract

This theme issue covers topics at the forefront of scientific research on energy and the subsurface, ranging from carbon dioxide (CO 2 ) sequestration to the recovery of unconventional shale oil and gas resources through hydraulic fracturing. As such, the goal of this theme issue is to have an impact on the scientific community, broadly, by providing a self-contained collection of articles contributing to and reviewing the state-of-the-art of the field. This collection of articles could be used, for example, to set the next generation of research directions, while also being useful as a self-study guide for those interested in entering the field. Review articles are included on the topics of hydraulic fracturing as a multiscale problem, numerical modelling of hydraulic fracture propagation, the role of computational sciences in the upstream oil and gas industry and chemohydrodynamic patterns in porous media. Complementing the reviews is a set of original research papers covering growth models for branched hydraulic crack systems, fluid-driven crack propagation in elastic matrices, elastic and inelastic deformation of fluid-saturated rock, reaction front propagation in fracture matrices, the effects of rock mineralogy and pore structure on stress-dependent permeability of shales, topographic viscous fingering and plume dynamics in porous media convection. This article is part of the themed issue ‘Energy and the subsurface’.

Simulation of discrete cracks driven by nearly incompressible fluid via 2D combined finite‐discrete element method

“…This advantage is extremely important because it means that very fine meshes can be used around areas of interest, such as boreholes, without penalizing the computational cost as fractures propagate (ie, open) and the fluid flows through them. This is a great advantage over other recently introduced approaches that exhibit a dependency of the time step in the form of Δt crit ∝ (l/a) 2 where l is the element size and a is the fracture aperture. This paper presents a series of benchmark cases for the proposed solver.…”

“…1 The coupling of rock mechanics to fluid flow has become a critical topic for understanding the performance of energy systems including the production of unconventional oil and gas (eg, hydraulic fracturing) where fluids are used either to create new fractures or to prop open pre-existing ones with the aim of increasing the permeability of formations. 2 This is the case of low permeability shale reservoirs, where hydraulic fracturing is used to make the extraction process economically feasible. Accurate fluid-driven fracture simulations are critical for predicting and optimizing fracture height growth at hydraulic fracturing sites for optimum reservoir management.…”

“…The cross‐cutting theme of “Controlling subsurface fractures and fluid flow” has been identified as a key to increase extraction efficiencies while reducing the environmental footprint in a recent U.S. Department of Energy report . The coupling of rock mechanics to fluid flow has become a critical topic for understanding the performance of energy systems including the production of unconventional oil and gas (eg, hydraulic fracturing) where fluids are used either to create new fractures or to prop open pre‐existing ones with the aim of increasing the permeability of formations . This is the case of low permeability shale reservoirs, where hydraulic fracturing is used to make the extraction process economically feasible.…”