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

Abstract

Summary The Pelican Lake heavy-oil field in northern Alberta (Canada) has had a remarkable history since its discovery in the early 1970s. Initial production by use of vertical wells was poor because of the thin (less than 5 m) reservoir formation and high oil viscosity (800–80,000-plus cp). 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. However, with primary recovery at less than 10% and 6.4 billion bbl of oil in place (OIP), the prize for enhanced oil recovery (EOR) is large. Initially, polymer flooding had not been considered as a viable EOR technology for Pelican Lake because of 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 learned and a second pilot was met with success in 2006. The response to polymer injection in this pilot was excellent, with oil rate increasing from 43 BOPD to more than 700 BOPD and remaining high for more than 6 years; the water cut has generally remained at less than 60%. Incremental recovery over primary production is variable but can reach as high as 25% of oil originally in place (OOIP) in places. This paper presents the history of the field and 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 currently, standard industry-screening criteria limit its use to viscosities up to 150 cp only. Pelican Lake is the first successful application of polymer flooding in much-higher-viscosity oil (more than 1,200 cp), and as such, it opens a new avenue for the development of heavy-oil resources that are not accessible by thermal methods.

Polymer Flooding of Heavy Oil - From Screening to Full-Field Extension

“…Field results obtained to date suggest that maximum acceptable live oil viscosity could be as high as 5,000 cp (Delamaide et al 2013, Delamaide et al 2014c, Renouf 2014. Polymer injection has been successfully tested in viscosities as high as 10,000 cp (Delamaide et al 2014c) however the efficiency of the process seems to diminish as viscosity increases and in particular water-cut can increase to high values even with polymer.…”

“…It is extremely important to obtain representative water samples; one common issue that happened both in the first polymer flood pilot in Pelican Lake (Delamaide et al 2013) and in Bodo (Wassmuth et al 2009) is that if the water samples get in contact with oxygen and if iron is present in the water, it can precipitate and remain undiscovered. As discussed in the Screening section, polymer is highly sensitive to iron and that needs to be taken into account when designing the facility.…”

“…This larger gradient may not always be sustainable in the field. • In Pelican Lake injected solution viscosity in the first pilot was 100 cp and this was probably one of the causes for the failure of the pilot (Delamaide et al 2013). • For most field cases summarized in Table 4, injected polymer viscosity was in the 20 -50 cp range even when oil viscosity was higher and in similar reservoir settings (free crossflow with variable permeability).…”

“…If that happens then the causes need to be identified and corrective action need to be taken -if at all possible. In the second Pelican Lake pilot for instance the injection pressure was increasing faster than expected so this was integrated into the reservoir simulation model; a new history match was performed and as a result it was decided to reduce the molecular weight of the polymer (Delamaide et al 2013). …”

“…In Canada the largest heavy oil polymer flood in existence in Pelican Lake has hundreds of injection wells in an oil with a live oil viscosity ranging from 800 to over 10,000 cp (Delamaide et al 2013, Delamaide et al 2014c. In Seal after a successful pilot (Delamaide et al 2014a) the injection has been extended to 14 wells and the live oil viscosity varies from 3,000 to 7,000 cp (Murphy Oil Company Ltd. 2014).…”