From Ordovician Source Rock to Dolomitized Devonian Limestones: A Promising Exploration Model in Gaspésie, Eastern Canada

Jean-Sebastien Marcil¹, Jean-Yves Lavoie¹, Valérie Lavoie², and Virginie Lavoie^2
1 JUNEX, Quebec, QC
² Junex,

Gaspésie is a 20 000 km2 peninsula located in the southeastern part of Québec. Devonian carbonates of the Galt field are the only producing hydrocarbon reservoirs but several surface seeps in Devonian sandstones are known. Through recent exploration programs in Gaspésie, JUNEX proposes an innovative exploration model.

Based on Rock Eval and thermal maturation studies, an Ordovician marine oil-prone black shale source rock is recognized. Analysis yielded TOC values ranging from 4 to 10% with initial hydrocarbon potential up to 100 kg HC per ton of rock. The Ordovician oil migrated along regional extensional faults and fed the potential Silurian-Devonian reservoirs. Surface core sampling and outcrop studies suggest good reservoir potential for Silurian reefs, Silurian-Devonian hydrothermal carbonate breccias and Devonian sandstones. In three JUNEX wells, oil, gas, condensates and HTD are reported. On the basis of 2000 km of re-evaluated ground seismic data together with two high-resolution aeromagnetic surveys, a new exploration model is proposed. The model focuses on the high potential of hydrothermal dolomite reservoirs related to strike-slip faulting in a Silurian-aged extensional basin and the potential of shallow stratigraphic traps in the Devonian deltaic fans or channels sands.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005