Abstract

Heavy and extra-heavy oil reservoirs located in Western Canada (Alberta and Saskatchewan provinces) collectively represent one of the largest accumulations of hydrocarbons in the world. Over the past 20 years. a sustained field and laboratory research program aiming at economic recovery of Canadian heavy and extra-heavy oil has taken place. This has resulted in the development and commercialization of many recovery processes using steam. Current production from active projects is about 18,000",J per day. To cope with the large variation of geological and petrophysical conditions found in such oil reservoirs, a wide variety of successful steam-based recovery processes have evolved. These include steam stimulation above and below fracture pressure, pressure cycle steam drive, steam drive, and steam-assisted gravity drainage from both underground and surface access. The principal mechanisms believed to be taking place in each case will be outlined. Pertinent applications of each steam process in relationship to the micro and macro description of the reservoir essential to economic recovery are discussed. It will be shown Iww particular recovery processes were developed to match the geological and petrophysical properties at each particular site.

Introduction

Alberta and Saskatchewan have vast heavy oil and bitumen reserves. They are part of a variety of deposits ranging from Upper Devonian to Mississippian limestones and dolomites, to Lower Cretaceous sand deposits of continental to marine shoreline origin. Each deposit has distinct characteristics which require unique recovery technologies. This wide variety of recovery technologies, with emphasis on the use of steam, will be discussed in this paper. The heavy oil and bitumen deposits have been known for centuries, but research began in the late 1940s when large amounts of conventional oil were discovered nearby. Commercial production of heavy oil began in the late 1960s. In the early 1970s, when the oil price increased and Canada's conventional oil production and reserves were already declining, heavy oil production and research expanded rapidly. To stimulate this development, the Alberta Government established the Alberta Oil Sands Technology and Research Authority (AOSTRA) in 1974. Since then, AOSTRA, by collaborating with the Canadian petroleum industry has been a major player in the development of the current technology. This paper describes briefly the geology of the main deposits and the steam-based technology which has been most effective for each geological setting.

GEOLOGICAL FEATURES

Figure I shows the deposits in five major geographic locations: Athabasca Oil Sands Area, Cold Lake Oil Sands Area, Peace River Oil Sands Area, Carbonate Trend (Triangle) underlying the Athabasca and Peace River Oil Sands Areas, and Heavy Oil Bell.

The largest of these deposits may be the Devonian Grosmont Formation found in The Carbonate Tread. Because of low porosity, high variability and poor reservoir definition, this formation is most difficult to exploit Although bitumen-bearing carbonates have been encountered throughout northeastern Alberta, only limited drilling has been done, and reserves are poorly defined.

The deposits occurring in unconsolidated Cretaceous sands have been well delineated. The most recent oil-in place and initial established reserve figures arc shown in Tables I and 2.

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