Deep Devonian Reservoirs

Exploration For Deep Devonian Reservoirs, Northeastern British Columbia – New Perspectives

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Summary:
Location: Blocks SE: TWP84 R14W6, NW: 94-N-16
Strata: Devonian
Year of Study: 2005

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Introduction

North American gas demand and prices are escalating rapidly as we enter the 21st century, and the petroleum industry is searching for new exploration areas and ideas to satisfy these needs. Northeastern British Columbia is an ideal “new” exploration area which offers: high-impact (large reserves, high deliverability) exploration prospects; a proven record of world-class gas discoveries; abundant available acreage, including new land offerings in the Muskwa Kechika Management Area; excellent infrastructure, with capacity available in major pipelines; and promotion of exploration activity by the provincial government, including new incentive programs.

Background to the Area

Deep Devonian reservoirs, including the Chinchaga, Keg River, Sulphur Point, Pine Point, and Slave Point formations, are prolific gas producers, but are only lightly explored over much of northeastern B.C.. The Geological Survey of Canada (2000) and Canadian Gas Potential Committee (2001) estimate that several TCF of gas remain to be found along established play trends, and project substantial additional potential in conceptual exploration plays. The recent discovery of several hundred BCF in the Slave Point at Ladyfern is just one example of realizing this potential.

Exploration programs, particularly for smaller companies or new players, are hindered by the lack of a comprehensive understanding of deep Devonian reservoirs. Consequently, most organizations find it difficult to formulate a systematic, economically sound exploration strategy.

Geologic Setting

This study reviews the Middle Devonian stratigraphic framework of northeastern B.C. The paleogeographic settings that have been identified in this study are mainly the Platform and the Horn River basin. The edge of the platform bounds the basin from the west of Clarke Lake to the east of the Junior channel. The platform bends to the north through to the border of the Northwest Territories. The platform extends southwards to the Peace River Arch along the eastern border of the study area. On the basinal side of the shelf margin of the platform, many pinnacle reefs have been developed as isolated build-ups. In addition to reefal developments, many interior platform embayments have been recognized and a western platform edge has been hypothesized.

A comprehensive reconstruction of the structural framework is critical to the understanding of the petroleum prospectivity of the study area. Using regional aeromagnetic intensity mapping, basement lineaments, and structural offsets mapped in younger strata, Petrel Robertson Consulting Ltd. has identified regional networks of southwest-northeast and northwest-southeast faults, in addition to the Bovie Lake Fault Zone in the northwest and the Hay River Fault Zone in the southeast. Reactivation of deep-seated fault trends appears to have exerted control over large-scale features such as trends of platform margins and interior platform embayments, and over smaller features such as localization of isolated reefal buildups. Fault movements, particularly those involving strike-slip motion, have also allowed deep-sourced fluids to access the Devonian reservoirs, causing widespread reservoir enhancement, primarily through hydrothermal dolomitization and associated solution and brecciation.

Seven major hydrodynamic regimes in the middle Devonian have been identified by analyzing the pressures and fluid chemistry data from 1635 DST’s and a total of 303 production tests. Several have regional lateral continuity and some are hydraulically isolated.

Exploration potential can be classified into several play types for each prospective formation, depending upon the reservoir characteristics and regional paleogeography of each.

Methodology

A stratigraphic framework was constructed, based upon established lithostratigraphic criteria, using a regional correlation network of seventeen cross-sections, seven east- west and ten north-south. Formation tops were picked and assigned quality codes, reflecting quality and presence of log data for more than 1350 wells, including all wells penetrating the entire Devonian section. Well logs were also employed to calculate net porosity values, using a cut-off of 5%. In the course of this study a database and a suite of isopach, porosity, structural and paleogeography maps have been created.