Poromechanical behaviour of a surficial geological barrier during fluid injection into an underlying poroelastic storage formation

Abstract

A competent low permeability and chemically inert geological barrier is an essential component of any strategy for the deep geological disposal of fluidized hazardous material and greenhouse gases. While the processes of injection are important to the assessment of the sequestration potential of the storage formation, the performance of the is important to the containment potential, which can be compromised by the development of cracks and other defects that might be activated during and after injection. This paper presents a mathematical modelling approach that can be used to assess the state of stress in a surficial caprock during injection of a fluid to the interior of a poroelastic storage formation. Important information related to time-dependent evolution of the stress state and displacements of the surficial caprock with injection rates, and the stress state in the storage formation can be obtained from the theoretical developments. Most importantly, numerical results illustrate the influence of poromechanics on the development of adverse stress states in the geological barrier. The results obtained from the mathematical analysis illustrate that the surface heave increases as the hydraulic conductivity of the caprock decreases, whereas the surface heave decreases as the shear modulus of the caprock increases. The results also illustrate the influence of poromechanics on the development of adverse stress states in the caprock.

An analytical plane-strain solution for surface uplift due to pressurized reservoirs

“…The right-hand-side of the equilibrium balance (4) could include a term representing buoyancy of supercritical CO 2 being less dense than brine. The following analysis is single phase and the eventual uplift from buoyancy is not accounted for, as commonly done with analytical models [15,36,37]. The effective stress τ ij can be written as the sum of the initial effective stress τ…”

“…Notice that the solutions (36) and (37) for v and w, respectively, do not contain the elastic parameter γ. The reason for that is that both v and w are also solutions of the biharmonic, ∇ 4 v = 0 and ∇ 4 w = 0, which is a parameterless equation, see Fung [12].…”

“…The reason for that is that both v and w are also solutions of the biharmonic, ∇ 4 v = 0 and ∇ 4 w = 0, which is a parameterless equation, see Fung [12]. Inserting the solutions (36) and (37) into equations (34) and (35) lead to c = k, w 1 = −v 1 and w 2 = v 2 . The boundary condition w = 0 for z = 0 gives that v 1 = v 2 , which is conveniently represented as w 0 /2.…”

“…An early example of a subsidence model, based on poroelasticity and cylinder coordinates, was developed by Geertsma [14,15]. Selvadurai [36], Kim and Selvadurai [18], Selvadurai and Kim [37], Niu et al [26] have developed analytical models for different configurations of a reservoir and a caprock. Selvadurai and Kim [37] present analytical poroelastic solutions for a storage aquifer with a caprock, when there is a steady injection into a circular injection zone.…”

A Three-Dimensional Analytical Solution for Reservoir Expansion, Surface Uplift and Caprock Stress Due to Pressurized Reservoirs

“…They use a numerical method to fit a set of analytical solutions to approximate the boundary condition in an optimal manner. Selvadurai (2009), Kim and Selvadurai (2015), Selvadurai and Kim (2016) and Niu et al (2017) have developed analytical models for different configurations of a reservoir and a caprock. Selvadurai and Kim (2016) present analytical poro-elastic solutions for a storage aquifer with a caprock; the solutions are given by an integral representation.…”