ABSTRACT

The Ring/Border Field straddles the British Columbia/Alberta border, 175 km northeast of Ft. St. John. It is a recent shallow gas discovery in the Triassic Montney Formation, with additional reserves in the Cretaceous Bluesky and Gething formations. Since 1988, an aggressive exploration and development program has resulted in the drilling of 90 wells with possible reserves up to 1 TCF (28.3 10⁹m³), and initial deliverability of greater than 100 MMcf/d (28.3 10⁵m³). The Ring/Border Field is a complex stratigraphic-subcrop trap that has been delineated through the integration of geology, petrophysics, and hydrodynamics.

The Triassic Montney Formation, the main reservoir, is a sequence of tidally-influenced shoreface sands, silts, and shales. The reservoir sands are mature, very fine grained sublitharenites with excellent secondary porosity. The Triassic dips to the southwest, and is cut by numerous northeast-southwest trending faults subparallel to the Hay River Fault System. The pre-Cretaceous unconformity erosionally truncates the Triassic, and during the last stages of erosion, valleys were incised. In Gething time, these valleys were filled with flood-plain coaly sands, silts, and shales. Sands within the valleys are of reservoir quality, but are thin and discontinuous. The Bluesky Formation is a transgressive lag deposit that blankets the area. It is up to 4 m thick, and varies from a medium grained, glauconite-rich litharenite to conglomerate. Although the Bluesky Formation is laterally continuous, good reservoir within the Bluesky is sporadic.

Early recognition of this subtle trap was due to creative integration of detailed sedimentological studies, high-resolution logging techniques, and innovative drillstem test interpretation. The size and quality of the Ring/Border Gas Field demonstrates that giant conventional fields may still be found within the Western Canada Sedimentary Basin.

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