New Insights in the Structural and Tectonic Evolution and Petroleum Potential of the Orphan Basin, Atlantic Canada

Michael Enachescu¹, Steve Kearsey², Victoria Hardy², Jean-Claude Sibuet³, Shiri Srivastava⁴, John Hogg⁵, Jerry Smee⁶, and Alphonsus Fagan⁷. (1) Memorial University, St. John's, NF, Canada, phone: 709-737-6103, michaele@mun.ca, (2) Memorial University, (3) Ifremer Centre de Brest, B.P. 70, Plouzane Cedex, 29280, France, (4) Geological Survey of Canada Atlantic, (5) EnCana Corporation, P.O. Box 2850, 150 - 9 Avenue SW, Calgary, AB T2P 2S5, Canada, (6) ExAlta Energy, Canada, (7) Newfoundland Department of Mines and Energy, Government of Newfoundland and Labrador, St. John's Newfoundland, NF, Canada

The Orphan Basin, offshore Newfoundland, is a wide continental rift located northeast of the petroliferous Jeanne D'Arc Basin. The Orphan Basin formed during the Mesozoic intra-continental extension, continental break up and Atlantic Ocean opening. Based on the period of main tectonic subsidence, the large basinal area was subdivided into a gas prone West Orphan Basin with mostly Early to Late Cretaceous sedimentary fill, and oil prone East Orphan Basin with Jurassic and Cretaceous sedimentary fill. During basin evolution, Flemish Cap microplate rotated clockwise and moved to the southeastward, with East Orphan Basin facing the Porcupine Basin and the West Orphan Basin opposite the Rockall Trough.

An integrated geophysical interpretation was conducted using modern pre-stack time migrated, 12-second, seismic data donated to Memorial University of Newfoundland, and the Geological Survey of Canada's (GSC) suite of offshore free air gravity and total field magnetic data. Large North-South and Northeast-Southwest trending basement ridges with interlaying troughs, were identified on seismic data and interpreted as basement highs or sediment covered ridges. A variety of potential field depth-to-basement techniques were applied to assist with basement interpretation. Large basement cored ridges and domes overlain by syn-rift sediments or rollover anticlines in the downthrown of major faults are the main structural traps in the East Orphan Basin, where expected source rocks are Kimmeridgian shales. Platform and ridge derived sand fans of Late Cretaceous and Early Tertiary age, sourced from a postulated Albian or Late Cretaceous source rock are the undrilled play in the West Orphan Basin.

Exploring North Atlantic Margins
2005 AAPG Annual Convention (June 19-22, 2005) Technical Program