Process Variables of In Situ Combustion

Abstract

Published in Petroleum Transactions, AIME, Volume 213, 1958, pages 28–35. Abstract This paper describes the results of a laboratory investigation conducted to obtain data for an evaluation of the in situ combustion process as a method of producing crude oil from reservoirs. Air and fuel requirements, rates of advance, combustion temperatures, and coke and fluid distributions are presented. The mechanism of oil recovery by in situ combustion is discussed. Five crude oils ranging in gravity from 10.9 to 34.2 API were produced from a semiadiabatic, unconsolidated sand pack by in situ combustion. Experimental conditions were varied over a wide range in order to determine the inter-relationships of process variables. The minimum air flux requirement for self-sustained combustion was found to be less than 10 scf/hr-ft. The rate of advance of a self-sustained combustion zone was found to be nearly proportional to the air flux at the combustion front. The effects of pressure and injected air flux were studied in a series of experiments using a 21.2 API crude. A minimum air requirement was observed at an air flux of 20 scf/hr-ft. The oil saturation consumed as fuel averaged 5.5 per cent of pore volume. The effect of air pressure was found to be small for experiments having high combustion efficiencies. This study should promote a better understanding of the problems and mechanisms involved in laboratory investigations and field applications of the in situ combustion process. The data presented will be useful in the interpretation of results of field tests. When tempered with volumetric sweep efficiencies, the data can be used in making preliminary economic appraisals of the process as applied to reservoirs containing high porosity unconsolidated media. Introduction The purpose of this work was to obtain laboratory data for an evaluation of the in situ combustion process as a method of producing crude oil from reservoirs. In situ combustion basically consists of (1) injecting air into a reservoir through selected input wells to create an air sweep through the reservoir,(2) igniting the crude at the injection well, and (3) propagating the combustion front through the reservoir by continued air injection. By this means, oil is swept toward producing wells in the area. The fuel for combustion is supplied by heavy residual material (coke) which has been deposited on the sand grains during distillation and cracking of the crude oil ahead of the combustion front.