Fosterton Northwest - A Tertiary Combustion Case History
Authors: Marberry J.E. , Bhatia S.K. 
Published: December 2007

This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., April 22–24, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
A tertiary dry forward combustion project has been in operation for four years in project has been in operation for four years in the Fosterton Northwest Unit, Northwest Roseray Sand Pool, located in southwest Saskatchewan. The favorable reservoir characteristics, including a small size and closed boundaries, were expected to result in a test which would provide basic data on the performance of the provide basic data on the performance of the combustion displacement process in a waterflooded pool. A severe injectivity problem limited the air injection rate to 0.9 MMscf/D for over a year, with the planned rate being 2.6 MMscf/D. Solution of this problem led to sustained injection at 2.1 MMscf/D for about two years. Performance at two air injection rates was thus observed. The oil production rate did not increase in proportion to the increase in the air injection rate. Two mechanisms for oil production are considered to be operating: thermal displacement and gas flooding. The contribution of each mechanism to total production is about equal at the present time and injection rate. An increase present time and injection rate. An increase of two- to five-fold in the air injection rate would be required to make thermal displacement the predominant production mechanism.

Introduction
Combustion is one of several tertiary recovery processes being examined by industry today. This paper presents a case history for dry forward combustion applied as a tertiary recovery process to a small reservoir in which a successful waterflood was approaching its economic limit. The reservoir is the Northwest Roseray Sand Pool of Fosterton Field (contained within the Fosterton Northwest Unit) located in southwest Saskatchewan, as shown in Figure 1. There are great potentials for a successful tertiary recovery scheme. As an example, it is estimated that significant tertiary reserves, some tens of millions of barrels, exist in pools in southwest Saskatchewan which are pools in southwest Saskatchewan which are similar in nature to the Northwest Rosersay Sand Pool of Fosterton Field. Pool of Fosterton Field. Fosterton Northwest Unit was chosen as the site of a pilot test because it contains a single moderately thick and uniform sand. The porosity and permeability values are porosity and permeability values are satisfactory. The sand is confined; this would prevent external influences from affecting the prevent external influences from affecting the performance. Although the waterflood had performance. Although the waterflood had recovered almost 82 per cent of the forecast reserves, sufficient oil remained in place to warrant a tertiary test.