A Current Appraisal of Thermal Recovery

Abstract

This paper identifies and assesses the importance of phenomena common to thermal recovery processes, discusses the extent of current operations, and anticipates the potential of these processes. The status of in-situ combustion, cyclic steam injection, and steam drive also is reported. Introduction Thermal recovery processes have been used extensively since the early 1950's. Emphasis during that first decade was on the in-situ combustion process, with the use of steam (in both cyclic injection and drives) coming of age in the following decade. These processes are by far the most commonly used thermal recovery methods, and this paper briefly discusses their status. paper briefly discusses their status. I assume that the reader is at least somewhat familiar with these thermal recovery processes, and if not that he can learn about them from the published literature. Selected references on the development, applications, appraisals, and reviews of each process are given in the references. It is not my intention process are given in the references. It is not my intention to discuss what is well established. Here, the emphasis is onidentifying and assessing the importance of phenomena common to thermal recovery processes, phenomena common to thermal recovery processes,discussing the extent of current thermal recovery operations, both in an absolute sense as well as relative to enhanced recovery processes other than waterflooding, andanticipating the potential of thermal recovery processes. processes. Brief Description of the Thermal Recovery Processes Processes In-Situ Combustion In-situ combustion (ISC), also known as underground combustion (UC), underground combustion drive (UCD), and fireflooding, is the name applied to a broad class of recovery processes in which part of the crude oil is burned in the reservoir. Air almost invariably is injected to support combustion processes. But these terms also are used to denote die dry forward combustion process, in which only air is injected and in which the process, in which only air is injected and in which the combustion front moves in the same direction (cocurrent) as the injected air.Variations of the dry forward combustion process include reverse combustion (also dry, with the combustion front moving countercurrent to the direction of the injected air) and wet combustion (a cocurrent process in which water is injected with the air). A number of terms are used to suggest the ratio of water-to-air injection rates in the wet-combustion process. Optimal wet, partially quenched, and superquenched are variations of the wet-combustion process, each succeeding term implying increased use of water. The wet-combustion process also is generally known as COFCAW (combination of forward combustion and waterflooding). Recycle-combustion is yet another process and is characterized by diluting the injected air with other gases, generally gases produced in the process itself, but the process seldom is used produced in the process itself, but the process seldom is used in oilfield operations.These variations of the combustion process arose from specific needs. JPT P. 1129