Most of Canada's trillion barrels of petroleum consists of bitumen, and to a lesser extent, heavy oil. This total may be compared with the total Canadian production of light-medium crude oil to date which is only 12 billion barrels. Mining is effective for the production of bitumen but is limited to the minor fraction of the resource that is shallow; also mining involves significant environmental difficulties.
The challenges of efficient in situ production are like those for other petroleum production activities:
to find and define suitable reservoirs,
to create conditions for oil to flow at economic rates and
to drain the reservoir systematically to obtain high recoveries.
This paper discusses the following in terms of production rate, recovery, energy requirements and economic factors. Each topic is a step, sometimes a sideways step, in the search for a means for achieving high rates and recovery within the bounds of economic constraints.
Cold production using vertical wells and horizontal wells.
Stimulation by wellbore heating.
Cyclic steaming using conventional wells.
Steam Assisted Gravity Drainage (SAGD).
Steam and Gas Push (SAGP).
Cyclic Steaming with horizontal wells.
Vapour Extraction (Vapex).
Processes resulting in the displacement of oil by gas to a lower horizontal well show the most promise. The viscosity in the region around the horizontal well should be reduced to allow economic rates without gas coning.
In SAGD, injected steam heats the oil and fills the reservoir as it drains, and rates of 500-1000 B/d can be achieved with bitumen recoveries greater than 50 %.. Heat savings can be achieved by building a substantial gas concentration within the depleted region (SAGP).
In Vapex, viscosity reduction is obtained by dilution with a volatile solvent; this is a promising approach for lower viscosity heavy oils.
Another promising approach is cyclic steaming with horizontal wells combined with gas addition to the steam to maintain drive.
As conventional oil reserves become depleted, interest continues to grow in the improved recovery and utilization of Canadian tar sands and heavy oil. The resources are enormous in magnitude and there have been great strides in technology. One approach, the mining and upgrading of shallow Athabasca deposits has, with the success of the Suncor and Syncrude projects, already become a major source of Canadian oil. Major expansions to both of these projects as well as other new tar sand mining projects are underway.
While mining overcomes the problem of moving the oil to the surface and of obtaining high recoveries, it requires the handling and disposal of vast amounts of solids and sludge and it is only economic for the shallowest of deposits. The major part of the Canadian oil sand resource is too deeply buried for mining to be practical.
This paper is concerned with the recovery of bitumen and heavy oils by in situ methods, i.e., by means of wells drilled from the surface. Cold production with conventional, near-vertical wells is only practical with oils of relatively low viscosity if reasonable production rates are to be obtained.