NATURAL GAS RESOURCE POTENTIAL OF THE CARBONIFEROUS MAGDALEN BASIN, GULF OF ST. LAWRENCE, EASTERN CANADA

The Carboniferous Magdalen Basin underlies the Gulf of St. Lawrence and Prince Edward Island, encompassing an area of 160,000 km². The basin is part of the broader Maritimes Basin that incorporates several late Paleozoic (post-Acadian orogeny) successor basins in Atlantic Canada. The Magdalen Basin contains up to 12 kilometers of continental and shallow marine strata, deposited in two major tectono-stratigraphic units: a lower Carboniferous succession of clastics and volcanic rocks in fault-bounded sub-basins, and a middle to upper Carboniferous (post-rift) succession of carbonates, evaporites and clastics. Coal beds are abundant in the upper Carboniferous. Basin structures are associated with rift faulting (and related inversion structures) and salt tectonics.

Petroleum exploration in the Magdalen Basin (principally in the 1970s and early 1980s) included acquisition of about 40,000 line-kilometers of seismic reflection data and drilling of 18 exploration wells (9 offshore and 9 onshore PEI). Most of the wells tested anticlines associated with salt diapirs and pillows. There was one significant discovery – the offshore East Point E-49 well encountered a gas zone in upper Carboniferous sandstones (with a tested flow rate of 5.5 million cubic feet per day). Gas shows were encountered in several other wells.

The Magdalen Basin is still under-explored and many large structures remain to be tested. The basin contains the key petroleum-system elements for a substantial natural gas resource potential, including mature gas-prone source rocks and widespread reservoir strata. One of the main exploration risks is associated with reservoir quality in deeper parts of the basin (below 2000 m). All gas shows encountered to date occur in low porosity sandstones. Evaluations of enhanced recovery techniques may become an important factor in assessing resource potential in tight gas sands. Other possible (unconventional) basin gas resources include coal-bed methane and basin-centered gas.