Heat advection and forced convection in a lattice code – Implementation and geothermal applications

Abstract

A three-dimensional thermo-hydro-mechanical numerical model has recently been enhanced with thermal capabilities to study the response of geothermal reservoirs to stimulation and production. In this paper, we present an effort to consider three relevant thermal mechanisms in an existing lattice code initially designed for hydraulic fracturing: a) thermal advection in the fluid; b) heat transfer by forced convection from the rock to the fluid; and c) accurate thermal conduction in the rock matrix considering the thermal boundary layer effect. A numerical implementation of the new coupled advection-forced convection logic as well as the coupling with the existing conduction logic in the commercial code XSite is summarized. The numerical solution is compared to analytical solutions for simple simulation cases. The new simulation capability is applied in a large-scale geothermal example to illustrate its performance.