Overview
TCGA has recently enhanced the thermo-hydro-mechanical (THM) contact algorithm in ParaGeo to include advective/diffusive heat flow, facilitating thermal advection via fluid transport along faults, a requirement for Geothermal and C02 modelling simulations. In these applications relatively cold fluid is injected into the formation and much of the initial heat transport is by advection rather than diffusion. Faults and Fractures may be represented in ParaGeo as either embedded features or discrete surfaces via the contact algorithm. Heat flow along faults is an important phenomenon, either by design in Geothermal applications or via C02 leakage in C02 sequestration applications. It is also a coupled problem as heat and flow along faults alter the THM state which may result in fault reactivation, where all the solution fields are strongly coupled. This is accommodated in ParaGeo by using a coupled THM contact framework which accommodates large fault offset, where the fluid and thermal flow along and across the fault is represented by tangential and normal constitutive models that may be dependent on the geomechanical state variables (aperture, stress, etc).
Description of Model
The validation benchmark model is multi-layered with two reservoir layers underlain and overlain by shale lithologies with an inclined fault traversing the middle layers. Fluid is injected in the lower reservoir layer and produced in the upper reservoir layer sited on either side of the fault. The simulation of well injection and production rates of 5000 m3/day with injected fluid temperature of 30°C is performed over 84 years.
Simulation Results
The evolution of the 34°C isotherm and temperature distribution through time are shown below. In (a) the hotter fluid from the lower reservoir layer is transported up and along the fault to the produced upper layer. In (b) the colder injection fluid from the lower injected reservoir replaces the hotter fluid previously transported up the fault. (c) shows the 34°C isotherm reaching the upper reservoir layer fault and (d) reaching the producer well.
