Combustion Front Behavior in Porous Media With Catalytic Agents

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSeveral experimental investigations have previously considered naturally occurring clays, metallic minerals and additives as catalytic agents to improve oil recovery during air injection and in-situ combustion processes. It is reported that these materials could change the morphology and surface properties of the porous medium ahead of the combustion front; thus, (1) increase hydrocarbon deposition ahead of the front, and (2) modify the kinetics of oxidation reactions inside the front. However, their on the combustion front dynamics has not previously been investigated under varying reservoir conditions. In this paper, we approach the problem using an analytical method based on large activation energies of the oxidation reactions. The model describes combustion front as a moving boundary layer in a uniform porous medium. It involves coherent propagation of low-temperature (fuelgenerating) and high-temperature (fuel-burning) reaction regions under the influence of reservoir heat losses; thus, it is suitable for investigating the role of catalytic agents on the front propagation. In the absence of these materials, it has been previously found that the reaction regions propagate closely spaced, thus reducing the influence of deleterious heat losses on the combustion front [6,7]. At low air injection rates, however, the peak temperature and propagation velocity of the front noticeably decrease; namely, the front approaches its extinction limit. Here, we propose that any possible improvement (whether catalytic or not) on combustion performance should preclude the observed temperature drop with the low injection rates. The presence of catalytic agents is consequently introduced to the model in terms of systematic variations in the reaction kinetics parameters, and deposited hydrocarbon/generated fuel amounts. It is found that, although kinetics influences the system dynamics, it may not improve the combustion performance due to a compensation effect. The improvement is rather due to an implicit role of the increased specific sand grain surface area on the hydrocarbon deposition ahead. The surface area promotes fuel deposition; hence, significantly increase total heat content of the combustion process in the reservoir. The work is important for developing guidelines to screen catalytic agents that could be used during the air injection processes.

Catalytic Effect of Transition Metallic Additives on the Light Oil Low-Temperature Oxidation Reaction

“…Besides, Akkutlu et al , and Adagulu et al , investigated the front performance in the presence of catalytic agents under reservoir conditions using an analytical approach. The proposed model described the front propagation in a homogeneous porous medium.…”