Production Practices In Petro-Canada's Heavy Oil And EOR Wells
Authors: Duncan Grant 
Published: March 2010

Petro-Canada operates a number of thermal and non-thermal projects in the oil sands and heavy oil areas of Eastern Alberta and Western Saskatchewan. These projects have been plagued with low pump efficiencies, slow rod fall, fluid pound, solids production and overloaded pumpjacks.

Petro-Canada's solutions to these problems on steam, fireflood and primary producers in unconsolidated sand formations are presented in this paper. Specific topics include completion practices, bottomhole pump designs, sand control equipment and production techniques.

Introduction

Production of heavy oil, whether on primary or with the assistance of enhanced oil recovery techniques, is far more difficult than recovery of conventional light oil. Production wells at Petro-Canada have gone through many stages of development. Earlier wells were designed to obtain both production and information. Cost effectiveness, reduced maintenance and improved production were the bases of later well designs. Standardized completions have evolved for primary (Fig. 1), steam (Fig. 2) and fireflood (Fig. 3).

Casings

All surface casing is 244 mm. 48.1 kg/m. H-40, ST+C. Heavy oil wells use large 178 mm production casing so that sand control devices can be installed if necessary, larger tubulars can be used to reduce rod fall problems, dual completions can be considered, and conversion a f a field from primary to EOR can be readily accomplished. Primary wells are completed with 178 mm, 29.5 kg/m, K-55 ST+ C casing. The preferred casing on thermal completions is 178 mm, 34.2 kg/m, MN-80, Buttress, landed in tension but not prestressed. Fireflood wells use non-exotic alloys for all of the wellbore except across the zone of interest, where nickel alloys are run.

Cements

Good cement bonds, with minimal loss of cement into formations are the main objectives of Petro-Canada's cementing programs. A typical primary cement would consist of Class "A" + 3% CaCl2 for the surface casing, 2: 1:4 Pozmix for the upper 70% of the production casing, and Class "G" + 3% KCl for the lower 30% of the production casing. Fireflood wells subsitute Ciment Fondue, extended with alumina silicate firebrick, for the lower 30% of the production casing. Steam wells are frequently located in areas where lost circulation of cement is a problem. The use of lightweight cements (1,400 kg/m3) reduces the loss of cement. Free pipe for the upper 20 to 30% of the well and wellhead growth of up to 0.6 m while steaming a well is not uncommon. A typical thermal cement for a steam well could consist of 50% Class G, 25% spheres and 25% Silica Flour. Foamed thermal cements have been used on a few wells.

Wellheads

Blowout preventors are bolted to 279 mm, 14 MPa slip-on casing bowls welded onto the surface casing. All production casings, whether primary or thermal, are landed in slips in the surface casing bowls. Primary wellheads are bolted directly to the surface casing bowl and consist of a 279 mm by 179 mm by 14 MPa tubing head with lock down screws, tubing hanger for 73 mm EUE tubing, 179 by 73 mm bonnet, 73 mm BOP, 73 mm Flow tee and 73 mm stuffing box.