Abstract

The Dover Project (formerly the Underground Test Facility) is the world's first field pilot of the Steam- Assisted Gravity Drainage (SAGD) process using dual horizontal well pairs to recover bitumen. There have been four phases of SAGD piloting at the Dover site thus far. The Phase B pilot, which consists of three 500m long horizontal well pairs spaced 70m laterally apart, has been on continuous operation since early 1993. Phase B reached the peak production rate of 300 m3/d or 100 m3/d per well pair on average in the middle of 1994. After sustaining the peak rate for about two years, the production has been in decline with a steady increase in steam-oil ratio. Research carried out in the past few years suggested that the addition of a suitable amount of non-condensable gases (NCG) would be an effective method to wind-down the steam chamber. It provides an economic means to continue bitumen production by utilizing the large amount of heat stored in the SAGD chamber. Beginning in April 1998, a small amount of natural gas was added continuously to the steam injection. The concentration of the NCG has increased steadily in the past 3.5 years. The resulting performance has been better than initially expected. Based on the success of this NCG-steam wind-down strategy, a four month flue gas injection test was conducted in 2001 to investigate the possibility of using the more cost effective flue gas than the natural gas as an injectant.

This paper summarizes the rationales of selecting the NCG-steam wind-down strategy, the field implementation of the flue gas injection test and the resulting pilot performance. The successful implementation of this technology will have profound impacts on the overall process economics.

Introduction

The Dover Project is an insitu bitumen recovery facility on the Oil Sands Lease Number 328 located 70 km northwest of the City of Fort McMurray. It was initiated by Alberta Oil Sands Technology and Research Authority (AOSTRA) in 1984 and was later joined by industry participants to pilot the SAGD process using dual horizontal wells. The Dover Project Area is located in 8 sections of land at the extreme eastern edge of the lease as shown in Figure 1. To the immediate east of Dover is Petro-Canada's MacKay River Project, which is expected to produce 30,000 BOPD using the SAGD process in 2003.

Several papers(1,2,3) have been published to describe in detail the Dover Project from the beginning till mid-1997. The following is a brief summary.

The first phase of testing, Phase A, involved the drilling of horizontal wells from a limestone tunnel network located about 20 m below the oil sand formation. These well pairs had a horizontal length about 60 m and were spaced 25 m apart as shown in Figure 2. They were operated from 1987 to 1991. Encouraged by the results from Phase A, the Project proceeded to the second phase of piloting in late 1991. In Phase B, the well pair length and lateral spacing were increased to 500 m and 70 m respectively.

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