Exploration of Conventional Resources

Conventional deposits consist of localized and properly described accumulations of natural gas. Gas is trapped in structural or stratigraphic reservoirs having characteristics correctly recognized where contact between the different phases (gas-oil-water) can be easily identified. Once they are discovered, these deposits are usually easily operated.

There are, all over the world, tens types of conventional deposits. Exploration of conventional resources here in Quebec groups according to four types :

• Collapsed or dolomitized zones in carbonates ( South-Central New York type or Albion-Scipio, Michigan)
• Overthrust belts (St-Flavien type)
• Dolomites ( Arbuckle type, Arkansas and Ellenburger, Texas)
• Paleozoic sandstone ( Innerkip type, Ontario, Glenwood-St.Peter, Michigan or Appalachian sandstone of Pennsylvania-Ohio)

Collapsed areas in carbonates are presently very popular exploration targets, since the lately discoveries of natural gas in New York State by a subsidiary of Talisman Energy. The same geological units (TBR : Trenton and Black-River) and the same structures ( extensional and strike-slip faults areas ) which contain New York prolific deposits exist in the St-Lawrence Lowlands. Deposits are contained in carbonate rocks reservoirs which have been altered and dolomited by hydrothermal fluids thus producing a depression and an increase of available porosity in the rocky massif. Recent studies and analysis of some wells from the St-Lawrence Lowlands indicate that the same process occurred in Quebec. Moreover, recent surface geological studies shown that similar process are acknowledged in Gaspesia in Silurian and Devonian rocks. Results coming from Galt #3 and Baillargeon #1 wells have also proven the presence of permeable and porous hydrothermal breccia in depth.

The best examples of Ordovician gas deposits producing from areas in overthrust belts are located in Oklahoma in the Anadarko Basin. Some deposits such as Sterling have recoverable reserves of natural gas of more than 25 Bcf . In this thrusted basin, the reservoirs units are either Ordovician carbonates (equivalent to Trenton and Black-River) or the Ordovician dolomites (equivalent to Beekmantown). In Quebec, the deposit of St-Flavien belongs to this type as well as the prospect of St-Simon does.

Many gas productions from the Appalachian and the South-West of the United States are coming from dolomite units of the Lower Ordovician. This unit stretches from Texas to the Labrador Coast. These units are equivalent to the Group of Beekmantown in the South of Quebec. Since the end of the eighties, many important deposits have been exploited or discovered in this type of formation in Oklahoma, in Arkansas and in the North of Texas and on the Labrador Coast. The dolomites of the Group of Beekmantown were among the most prospective for oil and gas exploration in Quebec. The dolomites indicate in subsurface, interesting petrophysical properties, as much in allochthonous than in autochthonous sequences. During the seventies and the eighties, SOQUIP tested some targets in the dolomites.

In Ontario, for nearly fifty years, the Innerkip deposit in the region of Kitchener has produced more than 25 Bcf from Cambrian-Ordovician sandstones. We can found these same porous sandstones in Quebec along the North Shore of the St-Lawrence. Many sandstones of same type are also production areas in different parts of the Appalachian Basin. In Michigan State, we can count 36 gas fields in Ordovician sandstones of Glennwood-St. Peter. Reserves for each well reach 2 to 14 Bcf and the reservoir properties of the formation stand from fair to excellent ( up to 15% porosity and more than 100 mD permeability).

Many indications of gas have been encountered in sandstones in Quebec without being largely developed. In the region of Innerkip deposit only, more than 250 wells have been drilled, this is more than all the wells drilled in the whole Lowlands in Quebec.

In its North-American context, the Quebec sedimentary basin can be compared to many basins where important hydrocarbons discoveries were made, particularly during the last years.