Pub. Id:A009 (1970)

First Page:50

Last Page:90

Book Title:M 14: Geology of Giant Petroleum Fields

Article/Chapter:Geology of Beaverhill Lake Reefs, Swan Hills Area, Alberta

Subject Group:Field Studies

Spec. Pub. Type:Memoir

Pub. Year:1970

Author(s):C. R. Hemphill (2), R. I. Smith (2), F. Szabo (2)

Abstract:

The discovery in 1957 of oil in the remote Swan Hills region, 125 mi northwest of Edmonton, began a wave of exploration similar to that following the 1947 Leduc discovery which started the postwar oil boom in Western Canada. By the end of 1967 more than 1,800 wells had been drilled to explore and develop the Swan Hills region. Drilling has established in-place reserves of more than 5.9 billion bbl of oil and 4.5 trillion ft³ of gas.

Devonian sedimentary rocks unconformably overlie an eroded Cambrian section in the southeast part of the Swan Hills region; in the northwest part of the region, Devonian rocks lap onto the Precambrian granite of the Peace River arch.

Three positive features--the Tathlina uplift, Peace River arch, and the Western Alberta ridge--profoundly influenced Middle Devonian Upper Elk Point and Late Devonian Beaverhill Lake sedimentation. An embayment, shielded on the north by the emergent Peace River arch and on the south and west by the nearly emergent Western Alberta ridge, provided an environment conducive to reef development in the central Swan Hills region. Carbonate-bank deposition flanking the Western Alberta ridge in the south and southwestern part of the study area persisted throughout the time of Beaverhill Lake deposition. These beds merge with the overlying Woodbend reef system.

Recent changes proposed in Beaverhill Lake nomenclature include the elevation of the Beaverhill Lake to group status and the Swan Hills Member to formation status. The term Swan Hills Formation, as used herein, refers to the reef and carbonate-bank facies of the Beaverhill Lake Group, whereas the term Waterways Formation is applied to the offreef shale and limestone facies. The Swan Hills Formation is considered to be equivalent in age to the Calmut and younger members of the Waterways Formation.

The Swan Hills Formation is divided into Light Brown and Dark Brown members. Swan Hills reefs attained a thickness greater than 300 ft, whereas the carbonate-bank facies commonly exceeds 400 ft in thickness. Changing sedimentary and environmental conditions produced a complex reef facies; six major stages are postulated in the development of the undolomitized reef from which the Swan Hills field is producing. Stromatoporoids are the dominant reef-building organisms; abundant Amphipora characterize the restricted lagoonal facies.

Although the total impact of Swan Hills production on the provincial economy is difficult to determine, the $184 million paid by the industry to acquire Crown lands in the region during the 10-year period after the initial discovery attests to the economic importance of the Swan Hills producing region.