Badger Play (Southwestern Ontario)

Retread Resources > Publications > Badger Play

by D.J. Nikols and P.W. Smit, Retread Resources Ltd.

Abstract

Oil has been continuously produced in southwestern Ontario for over 130 years, primarily from strata of Cambrian to Devonian age, at depths ranging from near surface (about 200 feet) to 4000 feet or more. The geological setting and hydrocarbon trapping mechanisms of the known oil and gas pools are discussed below, to illustrate the potential for undiscovered reservoirs in the Badger area. For additional background information, interested readers should consult reports by the Ontario Ministry of Natural Resources.

The Badger Play

Despite the long history of oil and gas production in southwestern Ontario, significant opportunities to discover new pools still exist. The Badger Play represents one such opportunity. Our preliminary studies have determined that the key elements that are necessary for reservoir development are present in the Badger area, and we believe that the area hosts a number of undiscovered pools. We are currently in the process of raising money for the seismic surveys that are necessary to pin-point the individual pools.

Regional Structural Setting

Much of southwestern Ontario lies on a shelf called the Algonquin Arch (or 'the arch' in this discussion). The arch separates the Appalachian Basin to the southeast from the Michigan Basin to the west, and geological formations from both basins lap up onto it. The arch was probably not a true, active upwarp feature, but appears to have formed simply because the basins subsided on either side of it. At times when the basins did not subside significantly, as was the case during the Ordovician, rock strata were deposited across the arch as if it did not exist (Bailey, 1986).

Having a passive role does not preclude deformation, however, and major faulting has occurred along the arch. Wrench-fault systems originating in basement rocks were reactivated periodically during Paleozoic time, and cross-faults developed in some areas to relieve the resulting stresses. Those faults have played key roles in creating hydrocarbon reservoirs, by allowing localized areas of dolomitization to form within the Ordovician and Cambrian limestones.

The Ordovician Formations

In the Ordovician section, the primary hydrocarbon-producing formations are the Trenton and Black River limestones. The reservoirs have developed along the reactivated faults, where dolomitization of fractured limestone has enhanced the porosity. The distribution of known Ordovician pools shows that pools can occur anywhere in southern Ontario as long as Ordovician limestones are present and are faulted.

The Cambrian Formations

The Cambrian section includes sandstones, dolomites and sandy dolomites. They are usually fairly porous, and for exploration purposes the Cambrian section may be thought of as a single prospective entity. Cambrian reservoirs include true stratigraphic traps, fault-bounded traps, and combinations of the two occur, and it is possible that some traps could involve both Cambrian and Ordovician strata.

Known Cambrian hydrocarbon pools (as of 1982) lie along the northern edge of the Appalachian Basin. For the most part, there has been little deep drilling along the Michigan Basin side, and we wonder why this is so. Geologically similar rock facies and similar geometry exist on both sides of the arch, and Cambrian pools should exist on both sides as well.

The Albion-Scipio Field

The Albion-Scipio (A-S) Field of Michigan is analogous to the situation that we expect at Badger. It lies on the south-central flank of the Michigan Basin, and is associated with a narrow, divergent basement fault system. Production comes from dolomitized Trenton and Black River limestones. Intermittent reactivation of the basement faults, especially during Siluro-Devonian time, led to faulting within the Paleozoic strata (Ellis, 1962), and created conduits that allowed dolomitization of the adjacent limestones (Harding, 1974; Buehner and Davis, 1968). The impermeable Utica shale provides a top seal for the reservoirs, and lateral seals are provided by tight, unfractured limestone.

The A-S Field is roughly linear in shape. The producing area, which is at no point more than one mile wide, is about 35 miles long, and trends northwest-southeast, subparallel to the fault system (Clark, 1988). It appears as a mildly synclinal depression in an area with an otherwise uniform dip of 33 feet per mile northward.

Summary

Situations analogous to those in the A-S field in Michigan and others in Ontario occur in both the Michigan and Appalachian Basins. The key features are (Inden, personal communication, 1996):

The reservoirs almost always form where dolomitization has enhanced the porosity of limestone host-rocks.

Dolomitization occurs along wrench-fault systems that were reactivated periodically during the Paleozoic, fracturing the Paleozoic limestones.
Where dolomitization has occurred, the porosity enhancement can cause vertical stratigraphic shrinkage, resulting in the development of syncline-like structures.
The wrench-fault systems can be very long (25 to 50 miles or more). They are often cut by younger cross-faults that act to compartmentalize the reservoirs.
The reservoirs function as fracture porosity systems. Lateral seals are a function of host-rock porosity (or the lack thereof), and shales act as top seals. Water legs are rare and small.
Seismic surveys are the best way to explore for these reservoirs, because many of the above features are recognizable on seismic sections
The most cost-effective approach is usually to locate the basement faults systems using comparatively inexpensive geophysical techniques. That information is then used to target the more expensive seismic surveys.

In the Badger area, we have identified a probable basement fault trend that extends for about 80 km. We believe that this trend could hold as many as 15 potential pools. We are in the process of raising money to perform the seismic surveys that are necessary to then identify individual pools.

References

Bailey, B., 1986. The hydrocarbon potential of the Cambrian, Ordovician and Devonian of Ontario. Ontario Department of Mines.
Buehner, J. H. and Davis, S.H. Jr., 1968. Albion-Pulaski-Scipio Trend Field. Michigan Basin Geological Society Symposium, p. 37-48.
Clark, S.L. and White, R., 1988. Seismic anomalies help to locate fractured production. World Oil, p. 63-68, Dec. 1988.
Ellis, G.D., 1962. Structures associated with the Albion-Scipio oil field trend. Michigan Geological Survey, p. 86.
Harding, T.P., 1974. Petroleum traps associated with wrench faults. American Association of Petroleum Geology Bulletin, v. 58, p. 1290-1304.
Inden, R., 1996. Personal communication.