Perspective of A Fireflood Process Using Low Air Injection Rates
Authors: Tsang P.W. 
Published: March 2010

A conceptual reservoir flow path model for fireflood in a heavy oil reservoir with initial oil mobility was presented in 1988(1). The concept of flow paths and low injection rates to enhance oil production was implemented in the operational strategy for the Husky Tangleflags Fireflood Project in the Lloydminster heavy oil field in Saskatchewan.

Significant events in the Tangleflags Project are presented to demonstrate the benefits of upgraded oils generated by the combustion process, and oil resaturation of the flow paths to enhance oil recovery. Incremental production was attributed to the fireflood process. Fireflood response was fairly evenly distributed in the pattern producing wells. No severe operational problem was evident compared to typical problems associated with firefloods predicated on a radial burn and displacement approach.

Introduction

The fire flood recovery process has been tested by Husky(2,3) in the Lloydminster heavy oil fields in Saskatchewan, and by others in various countries in the world(4). Fireflood continues to be the most viable recovery process for depleted heavy oil reservoirs with less than 8 m net pay but has not been demonstrated to be a commercial process in Canada, Most of the fireflood designs were predicated on a radial burn and radial displacement approach(5,6). Largely based on bum tube data, the air injection rare was designed to achieve a sufficient burn rate in the reservoir to displace and produce oil at an economic rate. Non-radial burn fronts, high casing pressures, elevated bottomhole temperatures, well damages and reduced productions were reported to be major problems(2,4,6).

A conceptual reservoir flow path model for firefloods in heavy oil reservoirs having some initial oil mobility was presented in 1988(1). The concept of flow parts was used to optimize the air injection rate, and the operational strategy in the Husky Tangleflags Fireflood Project. Significant events in the Tangleflags Project are presented to support the flow path model.

The produced oil viscosities in most wells were lower than the native oil viscosities, confirming the mixing of native oil with upgraded oils generated by the combustion process. The positive effects of fireflood were fairly evenly distributed among the pattern producing wells. No severe operational problem was observed compared to the problems associated with typical fireflood projects. Incremental oil recovery was achieved by fireflood using low injection rates in the largely depleted heavy oil reservoir.

Project Description

The Husky Tangleflags Fireflood Project was located in Section 13-51-25 W3 as shown in Figure 1. The project area had been produced on primary using 16.2 ha (40 acre) spacing since 1971. Over 120 × 103 m3 of oil was produced from Section 13 to the end of 1983. Two primary wells, A6 and A7, were converted to injection wells. One injection well, thirteen pattern wells and six offset wells were drilled and completed for this project in 1984 and 1985. The project consisted of three 12.1 ha (30 acre) inverted 7-spot patterns completed in the GP Formation as shown in Figure 2. Six offset wells were located around the three patterns to capture fugitive combustion gases.