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TitreSolid bitumen as a determinant of reservoir quality in an unconventional tight gas siltstone play
AuteurWood, J M; Sanei, H; Curtis, M E; Clarkson, C R
SourceInternational Journal of Coal Geology vol. 150-151, 2015 p. 287-295, https://doi.org/10.1016/j.coal.2015.03.015
Année2015
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140434
ÉditeurElsevier
Documentpublication en série
Lang.anglais
DOIhttps://doi.org/10.1016/j.coal.2015.03.015
Mediapapier; en ligne; numérique
Formatspdf
ProvinceAlberta; Colombie-Britannique
Sujetséchantillons carrotés; structure des pores; taille des pores; pyrobitume; bitume; hydrocarbures; maturation thermique; silstones; Formation de Montney ; Trias
Illustrationsphotomicrographs; schematic diagrams; graphs; histograms
ProgrammeCaractérisation des réservoirs de schiste, Les géosciences pour les nouvelles sources d'énergie
Résumé(disponible en anglais seulement)
In this study of the Triassic Montney tight gas siltstone play in the Western Canadian Sedimentary Basin petrophysical measurements of drill-core samples (porosity, pore throat size and water saturation) are integrated with pyrolysis data, organic petrography observations and SEM imaging to show that reservoir quality in the gas window is strongly influenced by the pervasive presence of solid bitumen (and pyrobitumen at higher thermal maturity). The solid bitumen formed as a pore-filling liquid oil phase that was diagenetically and thermally degraded with further burial and increase in temperature. The proportion of solid bitumen filling the intergranular paleopore network can be expressed as paleo-bitumen saturation (PBS) and this attribute is found to be the dominant control on pore throat size distribution. Samples with low PBS and large pore throat radius (>0.01 µm) have water saturations that generally increase as pore throat size diminishes, a relationship consistent with capillary theory for conventional water wet conditions. Samples with high PBS and small pore throat radius (<0.01 µm) have abnormally low water saturation, a condition inconsistent with capillary theory for conventional water wet rocks. The coincidence of small pore throat size, low water saturation and high PBS is attributed to the presence of well-connected nanopores within the devolatilized, solid bitumen and the hydrophobic nature of the bitumen. Siltstones in economic portions of the Montney tight gas fairway have porosity mostly in the range of 3 to 7% range. The results of this study show that reservoir quality in this economically key porosity range is influenced more strongly by PBS than by conventional determinants of porosity and permeability such as grain size, sorting, clay content and cementation. The concept of solid bitumen as an important control of reservoir quality elucidated here for Montney siltstones likely has application to the technical and economic evaluation of other tight gas plays particularly those in indirect basin-centered gas accumulations.
Résumé(Résumé en langage clair et simple, non publié)
Le présent article fournit des données exhaustives sur le rôle de la matière organique (bitume solide) dans la qualité du réservoir de gaz de la formation imperméable de Montney.
GEOSCAN ID295826