A coupled fluid–solid model for problems in geomechanics: Application to sand production

Some of the most challenging problems in geomechanics involve the coupling between fluid flow and solid deformation. In this paper we briefly present an overview of existing coupling methods to problems involving fluid flow and deformation and describe testing of a new discrete-based coupling method for problems in porous media. Modeled permeability and porosity distributions are compared to idealized packed assemblies and results are presented for simulations of steady flow through porous media. Previously published results for the coupled model focused on few or multiple particles in a fluid, whereas our results show good agreement to packed assemblies of particles (i.e. porous media). Finally, the two-dimensional model is applied to sand production, a common problem in geomechanics. Sand production is defined as the co-production of both a fluid and solid phase in oil and gas wells. In our models, we capture initial sand production associated with early-time drawdown. Later-time results show episodic sanding rates associated with formation stability and instabilities. Both observations are qualitatively consistent with laboratory and field observations. We find that high confining pressure inhibits the production of sand, through elevated interparticle contact forces. It is argued that these physically based models have a use in testing and evaluating competing hypotheses of sand production but their applicability is currently limited to small spatial and temporal scales. We believe these models bridge an important gap between the underlying physics of micro-mechanical interactions of fluid and solid grains and the continuum descriptions of those systems. Copyright 2010 John Wiley & Sons, Ltd.