Peace River Arch

Wabamun Project, Northern Alberta

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Summary:
Location: T72-88, R16W5-9W6
Strata: Wabamun
Year of Study: 1991

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Introduction

This study examines the nature, origin and distribution of locally developed Upper Wabamun dolomite reservoirs on the Peace River Arch (PRA), Alberta. The Tangent, Belloy, Eaglesham, CuIp and Cindy fields are within the project area; oil is produced in the eastern part of the area, gas in the west. General industry opinion is that these reservoirs have been formed by basement-controlled faulting; however, core examination suggests that they are more intimately associated with subaerial karst than with faulting. This study focuses on the role of underlying Leduc reefs, basement topography and intra-basement structural trends that spatially relate to karst solution caverns and associated porous dolomite within the upper part of the Wabamun.

The project consists of three separate sections which cover geological, aeromagnetic and hydrodynamic evaluations.

Available well records and logs of approximately 1000 boreholes were evaluated, and more than 3700 metres of core were logged. Regional stratigraphic cross-sections and local structural sections were constructed in order to determine stratigraphic correlations and the timing of karst development that precipitated the collapse of the overlying Banff-Exshaw into Wabamun caverns. A series of 1:250,000 scale maps was constructed. The biostratigraphy of the Famennian of western North America was evaluated in an attempt to define the stratigraphic level at which the karst features were produced. The geological component includes a text illustrated by photographs, cross-sections, core descriptions from representative wells and the following maps: Wabamun structure, Precambrian structure, Wabamun to Precambrian isopach, Upper Wabamun diagenetic lithofacies, and Wabamun production.

Most hydrocarbons discovered in the upper Wabamun of this area occur within karst-related dolomites along the Tangent-Eaglesham trend, or above the southeastern portion of the PRA Leduc fringing reef. This report identifies many additional boreholes that penetrate karsted Wabamun where there may be potential for associated dolomite reservoirs. The emphasis of the study is on factors that control local dolomite reservoirs within the upper Wabamun, and on the potential for further hydrocarbon exploration. An integrated prospect map based on geological, hydrological and geophysical interpretation is included.

Aeromagnetic data across the Peace River Arch were processed to produce a three-dimensional map of basement structures, in order to investigate possible controls on structural and facies trends within the overlying sedimentary column, in particular the Wabamun Formation. The report describes the survey data, processing procedures, interpretation criteria, geologic evaluation of existing play trends, and identifies prospective Wabamun fairways based on established stratigraphic and magnetic basement trends.

The delineation of basement trends, faults, and contacts was accomplished by the recently developed GRlDEPTHTM algorithm (trademark of the Robertson Group) that solves directly for source depth and location based on the observed magnetic field, calculated gradients, and a structural index term that geometrically describes the source. Maps included in the report are: Regional Magnetic Anomaly Index Map showing basement domains, Colour Contour Magnetic Anomaly Map, GRlDEPTHTM Map, and Basement Lineament Map.

The hydrodynamic evaluation is based upon analysis of 905 DST’s. The text is accompanied by a Pressure versus Elevation Graph and the following maps: Drillstem Test Recovery, Pool Delineation, Water Chemistry, Gross Wet Gas Percentage, Hydrogen Sulphide Distribution, Oil Gravity, Potentiometric Surface, Isotherm and Wabamun Trend Map.