Silver-Dahl

Exploration and Development Assessment of the Lower Cretaceous Section, Silver-Dahl Areas, Northeastern British Columbia

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Summary:
Location: Blocks SE : 94-H-8, NW : 94-H-12
Strata: Gething / Bluesky
Year of Study: 1998

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Introduction

Lower Cretaceous strata of the Silver/Dahl area are attractive exploration and development targets. Existing gas and oil reserves and good well control focused on deeper objectives allow us to assemble a regional study that outlines several exploration and development plays. The Silver/Dahl study adjoins and complements Petrel’s Buick Creek/Laprise study completed in 1997.

We create a comprehensive stratigraphic framework, using well logs, cores, petrography, hydrogeology and seismic data. The basal pre-Gething unconformity is the oldest element of the framework. It incises a complex valley system, which consists of a number of tributaries to the trunk drainage system defined in the adjacent Buick Creek – Laprise study area. Triassic strata underlie the unconformity throughout the Silver/Dahl area; there are no Jurassic or Buick Creek (latest Jurassic – earliest Cretaceous) units, as there are to the west and southwest. As relative sea level rose during the Early Cretaceous, lower Gething coarse clastics began to fill the main north-south valley. With continued transgression, fluvial to deltaic upper Gething strata infilled the remaining topography. The pre-Bluesky valley incision mapped in the Buick Creek – Laprise area was not observed at Silver/Dahl. Transgression of the Wilrich Sea, which deposited Bluesky sandstones along east-west shoreline trends, completely reworked any early Bluesky valley-fill strata that were originally deposited. Thick, areally-limited “Notikewin” deltaic sandstones occur higher in the section, but lack evidence of hydrocarbon charge, and exhibit limited reservoir quality.

Regional orogenic movements acting upon pre-existing structural elements profoundly influenced Lower Cretaceous sedimentation and subsequent trap formation. Columbian (latest Jurassic – earliest Cretaceous, and then later in the Early Cretaceous) reactivation of the Proterozoic Hay River Fault System produced block fault movements which dictated (in part) the routes of the pre-Gething valley system. These valley configurations are a primary control on deposition of Gething and Bluesky strata.

Hydrocarbon occurrences and potential are classified in terms of four play types built on the stratigraphic framework summarized above. Stratigraphic mapping and hydrodynamic interpretations indicate the presence of significant exploration plays and development prospects in:

1. sub-Cretaceous Triassic subcrop plays
2. lower Gething valley fill sandstones
3. upper Gething channel fill sandstones
4. Bluesky shoreface sandstones.

Careful stratigraphic mapping is essential to developing prospects in each of these plays. Seismic is a useful tool in detailing individual prospects and delineating new fairways in lightly-drilled areas. Economically attractive prospects can be generated incorporating multiple Cretaceous (and possibly deeper) objectives.