Coupled multiphase flow and poromechanics: A computational model of pore pressure effects on fault slip and earthquake triggering

Abstract

The coupling between subsurface flow and geomechanical deformation is critical in the assessment of the environmental impacts of groundwater use, underground liquid waste disposal, geologic storage of carbon dioxide, and exploitation of shale gas reserves. In particular, seismicity induced by fluid injection and withdrawal has emerged as a central element of the scientific discussion around subsurface technologies that tap into water and energy resources. Here we present a new computational approach to model coupled multiphase flow and geomechanics of faulted reservoirs. We represent faults as surfaces embedded in a three-dimensional medium by using zero-thickness interface elements to accurately model fault slip under dynamically evolving fluid pressure and fault strength. We incorporate the effect of fluid pressures from multiphase flow in the mechanical stability of faults and employ a rigorous formulation of nonlinear multiphase geomechanics that is capable of handling strong capillary effects. We develop a numerical simulation tool by coupling a multiphase flow simulator with a mechanics simulator, using the unconditionally stable fixed-stress scheme for the sequential solution of two-way coupling between flow and geomechanics. We validate our modeling approach using several synthetic, but realistic, test cases that illustrate the onset and evolution of earthquakes from fluid injection and withdrawal.

Wettability control on multiphase flow in patterned microfluidics

“…5). Pressure information in fluid-fluid displacement is of great practical interest in many subsurface technologies, including wastewater disposal (44), geologic sequestration of carbon dioxide (1), and hydraulic fracturing (45), because perturbations in the pore pressure are intimately linked with mechanical deformation of the medium (46).…”

Volume-Based Modelling of Fault Reactivation in Porous Media Using a Visco-Elastic Proxy Model

“…Different approaches have been developed to achieve this goal: Phase-field models represent a fracture interface by describing the change from broken and the intact rock diffusely with an order parameter (Mikelic et al 2015;Hofacker and Miehe 2013;Miehe et al 2010). Other approaches depict faults as discrete surfaces by means of zero-thickness elements using a penalty method (Ferronato et al 2008) or a Lagrange multiplier formulation (Jha and Juanes 2014). If the focus is shifted from the modelling of discrete fractures and fault surfaces towards the simulation of fault zones and their potential reactivation, the way these structures are geometrically represented changes: Accounting for the fact that faults zones are complex features consisting of a fault core and a damage zone, Rutqvist et al (2013) choose to model the fault not as a surface but as a fault zone instead, using a so-called ubiquitous joint model.…”

“…In a similar fashion, the description of the relevant physics during a slip event varies: It remains under discussion whether the coefficient of friction μ frict is a function of the slip rate and a state variable (accounting average maturity of contact asperities) such as used by Jha and Juanes (2014) or the slip weakening is rate independent (Garagash and Germanovich 2012) and can be modelled by transferring no normal and shear stresses (Ferronato et al 2008) or by a sudden reduction in the coefficient of friction (Cappa and Rutqvist 2011;Rutqvist et al 2013).…”

Reservoir Characterization in an Underground Gas Storage Field Using Joint Inversion of Flow and Geodetic Data

“…The forward model in our case is a one-way coupled flow and geomechanics model, which we simulate using our coupled flow and geomechanics simulator, PYLITH-GPRS [20].…”