Exploring activities conducted on Quebec territory allowed the discovery and exploitation of three natural gas deposits. These three deposits are Pointe-du-Lac (production of 2,5 Bcf), Saint-Flavien (5,7 Bcf) and Galt ( estimated well reserve to nearly 1 Bcf). Respectively, these three deposits were developed and operated by Laduboro, SOQUIP and Junex. The first two ones are depleted and now converted in natural gas underground storage while the third one is now in operation and in development under the supervision of Junex.

Pointe-du-Lac

Pointe-du-Lac deposit, located on the North Shore of St-Pierre Lake, was discovered in the middle of the 20th century. In 1955, Joseph Auger from Pointe-du-Lac was ending the drilling of a well started in 1948, up to 60 m in depth. As gas was coming out, he lost control of it and turned to experts in order to seal the leak. During the eruption, which lasted 72 hours, we estimate that 10 million cubic meters of gas escaped from the well.

In 1966, producing wells were linked together by a collector network. A gas pipeline dispatches gas towards some industries in Trois-Rivières. The exploitation of this deposit ended in 1976. The natural gas productive zone is located in the coarse well-sorted Quaternary sands and standing on the rocky shelf, 80 meters in depth. This gas is mixed (biogenic and thermogenic) and trapped in an aquiferous slightly salted, remains of the Champlain Sea and earlier glacial epoch.

Results from pre-feasibility analysis, conducted by many groups of which was the company JALTIN, indicate that the depleted field could be converted in an underground reservoir. So, in July 1990, for the first time in Quebec, the Ministry delivered an exploitation lease for an underground reservoir, to Intragaz.

Saint-Flavien

The natural gas deposit in Saint-Flavien was identified in 1972 following operation activities conducted by Shell Canada and the Société québécoise d’initiatives pétrolières (SOQUIP). The deposit was developed and in operation from 1980 to 1994, with a total production of 161 million m3 (5,7 bcf) in natural gas made of 95 % of methane without sulphur. The deposit is located about forty kilometres south-west of Quebec City. The structure of the field consists of an anticlinal fold formed by the setting of the overthrust of Saint-Flavien over Taconic orogeny period. The reservoir is lying in an allochtonous sequence of the St-Lawrence Lowlands platform and stratigraphically found in the dolomites of the Beauharnois formation of Beekmantown Group. In Saint-Flavien, gas is localized at two levels. A crystalline dolomite forms the reservoir level located in the median part of Beauharnois. This horizon is characterized by an inter-crystalline and vesicular porosity reaching 15%. A complex network of fractures largely increases the porosity and the permeability of the reservoir. The level of production of Lower Beauharnois, barely over Theresa Formation, is less developed than the previous one. It is constituted from a crystalline dolomite that sometimes looks like sandstone. The porosity varies from 3 % to 6 % and appears as inter-crystalline pores and opened fractures. The sedimentation environment, the tectonic of the region and the circulation of late-stage hydrothermal fluids allowed the development and preservation of opened fractures. These events increase the porosity by dissolution phenomena while the reservoir can accumulate hydrocarbons and maintain petrophysical properties favourable to deposit exploitation. Similar deposits are now being operated in Oklahoma, in Texas and in Arkansas in the South-West of the United States.

Since 1997, Intragaz has operated the most important underground storage site of natural gas in Quebec. This natural reservoir was developed straight from the former natural gas deposit of St-Flavien exploited by SOQUIP between 1980 and 1991.

Galt

Galt deposit was discovered at the beginning of the eighties following a first regional seismic geophysical survey made by SOQUIP in Gaspesia. However, the production of the deposit only started in 2002 after development activities carried out by Junex. Since Gaspesia is not linked by the pipeline, Junex produced gas thanks to the “compressed natural gas” technique that allows compressing gas then transport it via the road to the customer user. Daily production in natural gas for this deposit can be guaranteed by Galt #1 and Galt #3 wells which have a productive capacity of approximately 37 thousand cubic feet a day. We must also mention that with its natural gas production, Galt #3 well generates a daily flow of about 5 barrels of light oil.

Drillings carried out up to now allow us to attest that Galt deposit hydrocarbons producing zone is located a little bit over 2,000 meters in depth, on contact with Silurian rocks (Indian Point Formation) and Devonian (Forillon Formation) of Gaspé Basin. Rocky formations we found at these levels are dolomites and fossiliferous limestone slightly porous but fractured and modified by hydrothermal fluids. We must also add that in Galt region, the hydrocarbons saturated column is more than 2,000 meters in thickness. This means that from a 800 meters depth, every porosity of the rocky massif contains hydrocarbons (gas, oil or condensates). Contact between hydrocarbons and water has never been met even if drillings were carried out up to
2,700 meters deep.

Recent works in geophysics conducted by Junex allowed the identification of exploring targets that are very promising deeper in the basin. The challenge of Galt deposit consists in finding reservoirs where permeability and porosity would allow economical production of the important hydrocarbons column.