Role of catalytic agents on combustion front propagation in porous media
Conference Paper
Overview
Overview
abstract
Naturally occurring clays, metallic minerals and additives (catalytic agents) change morphology and surface properties of the reservoir matrix. In in-situ combustion processes these pore-scale modifications lead to variations in combustion front performance. It has been previously reported that catalytic agents have a dual effect on combustion: they modify the kinetics of oxidation reactions inside the front, and they increase the specific surface area of sand grains ahead of the front, promoting hydrocarbon deposition. The emphasis of this paper is the use of analytical approach to investigate the front performance in the presence of catalytic agents under reservoir conditions. The model describes front propagation in a homogeneous porous medium. The front involves coherent propagation of low-temperature (fuel-generating) and high-temperature (fuel-burning) reaction regions under the influence of reservoir heat losses. The catalytic agents are implicitly introduced to the model in terms of their dual effects. It is found that a strong catalytic effect exists due to changes in the specific surface area of hydrocarbons reacting with the injected oxygen. Variations in the activation energies of the oxidation reactions, on the other hand, are compensated by the reaction frequency (pre-exponential) factors, and they do not influence the combustion performance significantly. The catalytic effect is more pronounced at low air injection rates where heat losses are dominant. Changes in fuel deposition improve the combustion process, in particular at high air injection rates. Then, the front behavior is analyzed in a space of parameters that includes the catalytic agents. For analysis purposes, the space is divided into two sub-domains: one for the fuel generation efficiency and another for the dual effects. The results show existence of optimum conditions in the presence of catalytic agents. Such optimal reservoir conditions lead to frontal coherence and have the potential to significantly enhance combustion performance.
