“Tight gas” lacks a formal definition, and the term's usage varies considerably. Law and Curtis (2002) defined low-permeability (tight) reservoirs as having permeabilities of less than 0.1 millidarcies. Many explorationists think of tight or low-permeability reservoirs as occurring only within basin-centered or deep-basin settings.
Tight gas reservoirs occur throughout northeastern B.C. Three distinct regions can be recognized, based on structural and stratigraphic characteristics.
- Deep Basin — Characterized by stacked Mesozoic clastic reservoirs, each regionally pervasive and gas-saturated, containing abnormally-pressured gas accumulations lacking downdip water contacts. The updip (northeastern) boundary of the Deep Basin is difficult to determine, as each reservoir unit has its own updip edge.
- Foothills — Tight gas reservoirs of various ages and types produce where structural deformation creates extensive natural fracture systems. To the northeast, reservoir quality tends to be more conventional and fracturing plays a lesser role.
- Northern Plains — Laterally extensive tight gas reservoirs produce where relatively subtle natural fractures can be exploited with horizontal drilling and advanced stimulation techniques. Only one unit, the Jean Marie platform carbonate, is an established producer.