The Western Canada Foreland Basin: a basin-centred gas system

Abstract

Enormous volumes of gas (.30 Tcf ) are contained within the deepest portions of the Western Canada Foreland Basin, where tight gas-saturated Cretaceous sandstones grade updip into porous water-saturated sandstones. Production has occurred from coarse-grained shoreline sands both near the updip gas-water interface, such as those found in the Elmworth Field, and from low-porosity-permeability reservoirs found deeper in the basin. These basin-centred gas (BCG) reservoirs are characterized by regionally pervasive gas-saturated lithologies, abnormal pressures and no downdip water contact, and occur in low-permeability reservoirs. The keys to Shell's exploration success were an understanding of the stratigraphy, sedimentology and rock properties of the basin, the development of structural, petrophysical and geomechanical models, development of an understanding of the desiccation or dewatering process, the distribution of water within the basin and how the pressure regime evolved, interpretation of 3D seismic, and an aggressive land strategy. The evaluation of structural leads was aided when seismic and geomechanical modelling were combined, thereby aiding in the prediction of zones with a higher probability of encountering favourable reservoir producibility characteristics, that is, areas where a well developed, well connected open fracture network is expected. This multidisciplinary approach has resulted in economic success in regions once thought to be non-productive, and where it was once said, 'People go broke chasing the Nikanassin'.

From Seismic Quiescence to Surged Activity After Decades of Wastewater Disposal: A Case Study in Central‐West Alberta, Canada

“…The underlying Woodbend aquitard also effectively blocks the fluid from migrating downwards unless vertical faults act as conduits. Consequently, fluid injected into the Upper Devonian aquifer system can only migrate upwards along preexisting crustal faults and induce IIE at shallower depths (Boettcher et al., 2010). The occurrence of several events among cluster G2 below the injection depth appears to be inconsistent with our proposed model (Figure 2b).…”

Integration of Seismic Data and a Triple Porosity Model for Interpretation of Tight Gas Formations in the Western Canada Sedimentary Basin

“…Up to 7000 m of strata equivalent to the Nikanassin formation has been reported in the northwest and westernmost regions decreasing east and northeastward to a zero edge mainly due to the effect of a regional post-Valanginian unconformity, which truncates progressively older strata to east and north onto the craton (Stott, 1984(Stott, , 1998Poulton et al, 1994;Boettcher et al, 2010). This geometry is illustrated on the stratigraphic section shown on Figure 3.…”

Tight gas sandstone reservoir delineation through channel-belt analysis, Late Jurassic Monteith Formation, Alberta Deep Basin

“…Strata of the Monteith Formation are the deepest forelandrelated clastic reservoir targets within the Deep Basin of Alberta (Masters, 1979;Solano et al, 2010;Boettcher et al, 2010;Miles et al, 2012). As a result of deep burial and associated permeability degradation, the strata were historically overlooked and relegated to secondary or tertiary reservoir targets.…”

“…As a result of deep burial and associated permeability degradation, the strata were historically overlooked and relegated to secondary or tertiary reservoir targets. 14-23-063-12W6M) are associated with permeability enhancing natural fractures and have been targeted with vertical, deviated and horizontal wells (Boettcher et al, 2010;Miles et al, 2012). Production from the Monteith A is often produced (co-mingled) with uphole units, which results in complex production rates and trends.…”