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The AAPG/Datapages Combined Publications Database

CSPG Special Publications


Facts and Principles of World Petroleum Occurrence — Memoir 6, 1980
Pages 1000-1000
Symposium Abstracts

The Rainbow-Basset-Bluesky Gas Reservoir: A Second Generation Exploration & Development Project: Abstract

D. G. Smith1, L. H. Larson2

In early 1973, prompted by rising natural gas prices and a shallow basal Cretaceous Bluesky gas discovery by Universal Gas Co. Ltd. near Keg River, Alberta, a regional study of the Bluesky-Gething Formations of northern Alberta was begun by Canadian Hunter.

The consistent presence of the Bluesky sand over large areas, numerous gas drillstem tests, similar pressures and scarcity of water recoveries all pointed to the existence of a very large regional gas trap. The sand was deposited as part of a beach-delta-offshore bar sequence in a shallow, regressing Early Cretaceous sea. Gas productivity relates directly to sand permeability which is a function of three products of the environment of deposition — grain size, sorting and matrix.

Following the regional study, an aggressive policy of land acquisition through farm-in and Crown sales was begun in January 1974 by Canadian Hunter Exploration Limited.

The Basset well, Canhunter et al. Haig 10-34-104-3 W6M (1974) and the Rainbow well, Canhunter Haig 11-27-107-6 W6M (1975) both discovered major Bluesky gas accumulations.

Follow-up drilling in 1976 generally delineated the reservoirs at both Rainbow and Basset. The reservoirs occur at a depth less than 460 m (1 500 ft), consequently the pressures average only 2 480 kPa (360 psi.) With porosity of 22%, connate water saturation of 45% and dry sweet gas, the recoverable gas is 2 800 m3 (100 Mcf) per acre-foot. The Rainbow pool contains approximately 3.66 × 109m3 (130 bcf) and the Basset pool approximately 1.4 × 109m3 (50 bcf), underlying the lands developed by Canadian Hunter and its partner, Canadian Occidental Petroleum. Extensive muskeg throughout the area restricts drilling to the winter period of January through March. That, plus the remoteness of the area, makes the logistics of developing a field complicated and the costs high. In 1976 a gas purchase contract was negotiated and plans made to commence production in 1977. In the Rainbow area initial reservoir data made unitization on a hydrocarbon pore-volume basis impossible in time to commence production in 1977, consequently several companies entered into a unique pooling arrangement based on acreage ownership.

During the winter season of 1977 an intense development program enabled the operators to drill and complete additional deliverability wells, install pipeline gathering systems and construct compression and dehydration stations in both the Basset and Rainbow areas so that initial deliveries could commence in April 1977.

In spite of the remoteness of the area and the high cost involved, the work required to define the prospect, acquire land, drill, develop and connect the reserves was accomplished in less than four years.

Acknowledgments and Associated Footnotes

1 Canadian Hunter Exploration Ltd., Calgary, Alberta

2 Canadian Hunter Exploration Ltd., Calgary, Alberta

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