Jacques Burger

Chemical aspects of in-situ combustion--heat of combustion and kinetics

After general remarks on the oxidation reactions of hydrocarbons involved in in situ combustion, the heat releases are estimated and a formula is derived for computing the heat of combustion in the high temperature zone. Then a theoretical discussion of reaction kinetics in porous media is presented and applied to the in situ combustion processes. It is observed that there is some similarity between the kinetics of reverse and wet forward combustion processes. Furthermore, the influence of rock matrix properties on crude oil oxidation is illustrated by differential thermal analysis experiments. This observation is of great importance for practical applications. Some information concerning the use of low temperature oxidation data and the value of the reaction order with respect to oxygen partial pressure is derived from the interpretation of reverse combustion experiments using a numerical model. (16 refs.)

Laboratory research on wet combustion

The Institut Francais du Petrole carried out laboratory studies to simulate the in-situ combustion of crude oil by use of a 20 cm dia, 210 cm long combustion tube packed with sand. Following a series of dry combustion tests with oil and air, wet combustion tests were run by injecting water after the dry combustion had attained a steady-state velocity. A minimum water-air ratio of 0.001 cu m/std cu m was sufficient to overcome sand saturation and bring steam to the combustion front; a maximum water-air ratio of 0.004-0.006 cu m/std cu m caused extinction of the high-temperature zone. There was no coke deposit behind the combustion front as long as wet combustion took place with a high-temperature zone. Water injection led to more efficient heat utilization and to a higher combustion-front velocity.