Case Study of Successful Pilot Polymer Flooding to Improve the Recovery of Lloydminster Heavy Oil Reservoir- West Central Saskatchewan

Abstract

Abstract The Lloydminster Heavy Oil Block is the main source of Canada's conventional heavy oil production. The most common methods of recovery in this area are primary production, waterflooding, and chemical-enhanced oil recovery (EOR) such as polymer flooding. Although heavy oil waterfloods could be relatively successful if managed properly, their production and economic efficiencies are often challenging due to quick water breakthrough followed by a steep decline in oil production. Beliveau (2009) showed that over 50% of oil produced from such water flood projects are typically produced at water cuts greater than 90%, which would increase water processing costs. The objective of this study is to outline the implementation of a successful polymer flood project in Lloydminster Heavy Oil Block that includes the production and injection performance of the pilot. It also describes the steps of selecting the appropriate polymer type based on reservoir rock properties, water quality, and other main parameters for the optimal polymer selection. An anionic polymer candidate provided by ZL EOR Chemical Ltd. was selected for the project. The field under study is in the province of Saskatchewan and producing from the Lloydminster sandstone. Initially, the field was produced under a line drive waterflood with horizontal wells. The reservoir has a live oil viscosity of about 2,600 cP at downhole temperature of 21.5°C and the average clean-sand permeability of 1,500 mD. In April 2018, a polymer flood pilot was introduced as a primary recovery method with continuous polymer injection at ~25 cP (~2000 ppm polymer concentration). Injection rates varied from 30 to 50 m3/d/well, based on the target injection volume of 5 to 10% of effective pore volume (PV) per year. As a result, field water cut has decreased and stabilized at ~65%, while oil production rate has remained relatively constant at ~40 m3/d for over five years with no signs of polymer breakthrough. Production performance from the beginning of the polymer flood demonstrates the efficiency of this EOR method, thereby providing valuable insights into the first primary polymer flood project in the Lloydminster Heavy Oil Block.