  This paper is concerned with the analysis of the quasi-static
thermo-poroelastic model. This model is nonlinear and includes thermal effects
compared to the classical quasi-static poroelastic model (also known as Biot's
model). It consists of a momentum balance equation, a mass balance equation,
and an energy balance equation, fully coupled and nonlinear due to a convective
transport term in the energy balance equation. The aim of this article is to
investigate, in the context of mixed formulations, the existence and uniqueness
of a weak solution to this model problem. The primary variables in these
formulations are the fluid pressure, temperature and elastic displacement as
well as the Darcy flux, heat flux and total stress. The well-posedness of a
linearized formulation is addressed first through the use of a Galerkin method
and suitable a priori estimates. This is used next to study the well-posedness
of an iterative solution procedure for the full nonlinear problem. A
convergence proof for this algorithm is then inferred by a contraction of
successive difference functions of the iterates using suitable norms.
