Natural-Gas Potential in the St. Lawrence Lowlands of Quebec:A Case Study

Summary Since the announcement made in April 2008 concerning the shale-gas potential of the southern Québec lowlands, 30 new wells have been drilled in the area. The calcareous and organic-rich Middle Ordovician Utica shale is the main target of this recent exploration effort. Current knowledge of the area's geology has led operators to subdivide the shale-gas potential into different play types. To date, most operations have been performed in approximately one-third of the shale basin in the medium-to-deep thermogenic shale-gas play (1000 to 2000 m), located in the central part of the Saint Lawrence lowlands. With original-gas-in-place (OGIP) estimates ranging from 120 to 160 Bcf per section, the deep play is considered to be promising. Current efforts focus on determining the highest gas-prone unit within the Utica. The remaining two-thirds of the shale basin has not been largely tested yet, but the potential remains promising. On the basis of exploration work carried out over the past 5 years in southern Québec, four other play types have been described: (1) shallow-to-medium-depth thermogenic shale gas, (2) overthrusted shale gas, (3) biogenic shale gas, and (4) Intra-Appalachians subbasin shale gas. They are less explored than the deep-shale play, but also present interesting potential. This paper describes the previously mentioned plays using basin geology, shale mineralogy, organic-matter type, gas geochemistry, structural style, and infrastructure access. The characteristics of the previously described plays are reviewed from geological, geochemical, structural, and production perspectives. Results of evaluations using the concept of flow units, and volumes of OGIP calculated by various organizations, are compared with a recent evaluation using the petroleum resources management system (PRMS). It is concluded that there is promising hydrocarbon potential in the Saint Lawrence lowlands of Québec that continues to stimulate operators to pursue the exploration and development of these plays.