Pelican Lake Field: First Successful Application of Polymer Flooding in a Heavy Oil Reservoir

Abstract

The Pelican Lake heavy oil field located in northern Alberta (Canada) has had a remarkable history since its discovery in the early 1970s. Initial production using vertical wells was poor because of the thin (less than 5m) reservoir formation and high oil viscosity (600 to over 40,000cp). The field began to reach its full potential with the introduction of horizontal drilling and was one of the first fields worldwide to be developed with horizontal wells. Still, with primary recovery less than 10% and several billion barrels of oil in place, the prize for EOR is large. Initially, polymer flooding had not been considered as a viable EOR technology for Pelican Lake due to the high viscosity of the oil, until the idea came of combining it with horizontal wells. A first – unsuccessful – pilot was implemented in 1997 but the lessons drawn from that failure were learnt and a second pilot met with success in 2006. The response to polymer injection in this pilot was excellent, oil rate climbing from 43bopd to over 700bopd and remaining high for over 6 years now; the water-cut has generally remained below 60%. This paper presents the history of the field then focuses on the polymer flooding aspects. It describes the preparation and results of the two polymer flood pilots as well as the extension of the flood to the rest of the field (currently in progress). Polymer flooding has generally been applied in light or medium gravity oil and even today, standard industry screening criteria limit its use to viscosities up to 150cp only. Pelican Lake is the first successful application of polymer flooding in much higher viscosity oil (1,000-2,500cp) and as such, it opens a new avenue for the development of heavy oil resources that are not accessible to thermal methods.

Screening Criteria and Considerations of Offshore Enhanced Oil Recovery

“…Figure 7a shows two onshore cases with much higher oil viscosity than other cases; these are the Pelican Lake cases. Maximum oil viscosity in the Pelican Lake field is approximately 40,000 cP [48]. Such ultra-high oil viscosity may cause injectivity problems.…”

Supramolecular Polymer-Surfactant System for Heavy Oil Recovery

“…During waterflooding of heavy oil, "the adverse mobility ratio between the viscous oil and the water induces high-water-cut production and poor sweep efficiency" [2]. Polymer flooding decreases the mobility of the injected water (i.e., augmented water viscosity) reducing the watercut production levels.…”

“…Polymer flooding has been historically applied in light and medium gravity oil reservoirs. More recently, it has also been applied successfully in heavy oil reservoirs with oil viscosities ≥1200 cP, which expands the practical applicability of this EOR technique [2][3][4][5][6][7][8][9][10][11].…”

A new method for evaluating the injection effect of chemical flooding

“…Polymer flooding and surfactant-polymer flooding (SP flooding) are considered two of the most mature chemical methods (Chang et al 2006;Vargo et al 2000;Li et al 2012;Delamaide et al 2014;Sheng et al 2015). Polymer flooding uses high-molecular weight polymers to increase the viscosity of the injection fluid, and to decrease the oil-water mobility ratio, while the SP flooding further improves the oil recovery by adding a surfactant to the injection fluid to reduce the interfacial tension and then increase the oil displacement efficiency (Shen et al 2009;Urbissinova et al 2010).…”