The thermal recovery of heavy oil and bitumen from cool reservoirs via the injection of steam and hot fluids results in geochemical systems that are far from equilibrium. As a result, mineral and other solid grains in the reservoir may react with the injected fluid. These reactions often result in the dissolution of preexisting minerals and the formation of new ones. The types of minerals that form and their distribution in the reservoir may significantly impact reservoir quality, even to the point of blocking production.
If such deleterious phenomena occur, they can be irreversible. Consequently, it is prudent, when exploiting reservoirs with certain types of lithologies, to try and predict whether or not such formation damage is likely to occur. Computer simulations are the main tool for making such predictions.
This paper is intended to acquaint the reader with the basic type of analysis that can be done using a coupled flow/reaction geochemical computer code such as REACTRAN. Two basic reservoir types are used as examples, a carbonate reservoir and an immature sandstone reservoir. Two somewhat different lithologies for each reservoir type are used in the examples.
The examples show that different kinds of formation damage may take place. These include porosity gain that may lead to collapse, the formation of mineral fines from precipitation that may lead to fines migration problems, and the formation of clays and clay-like minerals that may occlude permeability.