ABSTRACT

In 1981, the Trapper Canyon tar sand deposit, Big Horn basin, Wyoming, was selected for investigation by the Bureau of Land Management (BLM) because the deposit was threatened by immediate trespass. The purpose of the investigation was to resolve conflicts between mining and leasing interests and to pave the way for commercialization of the deposit. The Combined Hydrocarbon Leasing Act of 1981 was of little use in the immediate development of the deposit; it did not “grandfather in” existing oil and gas leases. Conditions governing development of the deposit were a 1965 Interior Department Solicitor’s opinion based on the 1960 amendments to the Mineral Leasing Act of 1920, as reinterpreted by the BLM. The lessee must demonstrate that hydrocarbons can flow “naturally” by primary or secondary methods; tertiary recovery methods, are specifically excluded.

This administrative position has resulted in several expensive recovery projects for a relatively uncomplicated deposit.

There is no question that hydrocarbons underlie the area and that the most economical method of developing them would be to mine rather than pump the reservoir. There are serious questions as to whether the hydrocarbons of this deposit (2-5° API, 30,000 cp) can be induced to flow naturally. A water-injection, reverse circulation test was conducted on the Tensleep Sandstone reservoir of Pennsylvanian age in June 1983. Hydrocarbons were recovered at injection water temperature of 160-165°F (71-74°C) but not at the lower temperatures (reservoir temperature of 50-60°F, 10-16°C) requisite under the governing interpretation. The lessee has been authorized by the BLM to conduct an additional recovery project, injecting propane at reservoir temperature. On April 1, 1984, the lease expires automatically returning the Trapper Canyon deposit to the simultaneous oil and gas system or the competitive lease system.

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