Pelican Lake: First Successful Application of Polymer Flooding in a Heavy-Oil Reservoir
Authors: Wilson Adam 
Published: February 2015

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 165234, ’Pelican Lake Field: First Successful Application of Polymer Flooding in a Heavy-Oil Reservoir,’ by Eric Delamaide, SPE, IFP Technologies; and Alain Zaitoun, SPE, Gerard Renard, SPE, and Rene Tabary, SPE, IFP Energies Nouvelles, prepared for the 2013 SPE Enhanced Oil Recovery Conference, Kuala Lumpur, 2-4 July. The paper was peer reviewed and published in the August 2014 SPE Reservoir Evaluation & Engineering journal, p. 340.

Initially, polymer flooding had not been considered as a viable enhanced-oil- recover (EOR) technology for Pelican Lake in northern Alberta, Canada, because of the high viscosity of the oil until it was considered in combination with horizontal wells. Polymer flooding generally has been applied in light- or medium-gravity oil, and, even today, standard industry screening criteria limit its use to viscosities up to 150 cp. Pelican Lake is the site of the first successful application of polymer flooding in much-higher-viscosity oil (1,000–2,500 cp).

Introduction

The Pelican Lake field, approximately 250 km north of Edmonton, Alberta, Canada (Fig. 1), was discovered in 1978 and started producing in 1980. With more than 6 billion bbl of oil originally in place (OOIP) and a primary recovery estimated at less than 7%, it presents a significant target for EOR. But it is also a challenging reservoir with high-viscosity oil in a thin formation.

Early History

The reservoir-depletion mechanism is solution-gas drive, but initial reservoir pressure was low and there is very little dissolved gas, so there is little energy in the reservoir. Because the oil is also viscous (from 600 to 80,000 cp), primary recovery is low, approximately 5 to 10% of OOIP. In addition, the reservoir is thin (an average thickness of 5 m). As a result, the first wells drilled in 1980–81 were not economic.

Horizontal Drilling in Pelican Lake

CS Resources drilled its first horizontal wells in the Winter pool in Saskatchewan and then turned to Pelican Lake in 1987. Horizontal drilling is well-adapted to Pelican Lake, provided that the well can be maintained in the pay zone. Because the reservoir is so thin, a horizontal well can increase the reservoir exposure tremendously. The production performances of the horizontal wells were markedly better than those of the vertical wells and seemed to correlate reasonably well with the length of the horizontal drain in the reservoir. In 1991, CS Resources drilled its first openhole lateral arm from a main horizontal drain. Then, in 1993, it went one step further and drilled two multilateral wells with a new tool, the lateral-tieback system. The use of multilaterals would greatly expand in the years to come.

Screening of EOR Methods for Pelican Lake

Despite the improvement in recovery and overall economics resulting from the use of horizontal and multilateral wells, it was clear that primary recovery would be limited to 5–10% of OOIP, and other options were considered to increase recovery.