Current In-Situ Combustion Technology
Authors: Chu Chieh 
Published: December 2007

Abstract
This paper is a sequel to the state-of-the art review of fireflood field projects recently made by the same author, and discusses largely topics an current combustion technology which were not covered in the previous review. In this paper, examples are given to show why combustion was chosen as a primary, secondary or tertiary recovery process. primary, secondary or tertiary recovery process. Laboratory experimentation and numerical modeling in support of field projects are discussed. Expanded discussions are given an comparison between dry and wet combustion, and pattern selections. A review of monitoring and coring programs is followed by discussions on new frontier areas which include: in-situ combustion of tar sands and coal, utilization of flue gas, and a sand control technique.

Introduction
In-situ combustion, one of the most important enhanced oil recovery methods, has received increased attention in recent years. A state-of-the-art review of combustion field projects, recently made by Chu, covered the following topics: screening guides, reservoir performance predictions, project design, well completions, ignition methods project design, well completions, ignition methods and operational problems. This paper complements the previous review and discusses the following new topics: why combustion was chosen, laboratory experimentation and numerical modeling, monitoring and coring programs, and new frontier areas. Expanded discussions are also given on dry vs. wet combustion and pattern selection, which topics have already been touched upon in the previous paper. paper. WHY IN-SITU COMBUSTION
Most of the in-situ combustion field projects have been undertaken for secondary recovery purposes. However, in some cases, in-situ combustion was also used as a tertiary recovery process, and as a primary recovery process. In the following, examples primary recovery process. In the following, examples will be given to illustrate why in-situ combustion was used for recovering oil in various depletion stages of a reservoir.

1. In-Situ Combustion as a Primary Recovery Process
When Mobil started the combustion project in the Moco Zone Reservoir, Midway Sunset Field, California, the cumulative oil production by primary recovery means amounted to only 0.4% of primary recovery means amounted to only 0.4% of the original oil in place. The reservoir pressure was only slightly below the initial pressure of the virgin reservoir. It was expected that, without fluid injection of sane kind, there would be a rapid decline in the oil production rates. Reservoir properties appeared to be favorable for in-situ combustion. Predictions of performance under cambustion were made, based on the results of the South Belridge thermal recovery experiment and on prior supporting work. Evaluation of several modes of operation indicated that the most desirable economics would be obtained if the combustion process was applied immediately. Accordingly, process was applied immediately. Accordingly, combustion operations were undertaken as soon as practicable after the reservoir was returned to practicable after the reservoir was returned to production. production. Although examples are few in which in-situ combustion served as a primary recovery process, such a possibility should be examined and its economics evaluated. In commenting on the timing of initiating a combustion project for secondary recovery purposes, Poettmann stated that, the sooner the application of the combustion process to a reservoir, the better. Fireflooding a virgin reservoir is just one step further in the right direction.