Variations in Sequence Stratigraphy, Accommodation Space, Paleodrainage and Depositional Style


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The Jurassic-Cretaceous foreland basin of the Western Canada Sedimentary Basin (FB-WCSB) is considered one of the premier hydrocarbon provinces of North America. The FB-WCSB is characterized by multiple conventional and unconventional stacked reservoirs within in a deep basin system (DBS), and can be organized into:

  • A lower Underfilled foreland basin, with the main reservoir units associated with the Jurassic to Lower Cretaceous Nordegg, Poker Chip, Rock Creek, Fernie-Nikinassin, Mannville (and stratigraphic equivalents); and
  • An upper Overfilled foreland basin consisting of the Joli Fou, Viking, SWS, Cardium and Belly River (and equivalents).

An analysis of both the top 20 oil/condensate rates and top 20 natural gas rate wells (grouped on a boe/d basis from Alberta in 2015) were organized into pre-foreland basin, underfilled foreland basin and overfilled foreland settings. Fifteen of those wells were from pre-foreland deposits. Of the 25 top wells from the foreland basin:

  • 4/20 of the top 20 oil/condensate wells (20%) in the Deep Basin are characterized as occurring in the Overfilled Foreland Basin setting (Dunvegan, Belly River);
  • 1/20 of the top 20 oil/condensate wells (5%) are in the Deep Basin Underfilled Foreland Basin (Gething);
  • 20/20 of the Top 20 gas wells (100%) are Deep Basin Underfilled foreland Basin (Spirit River Group – Wilrich, Falher and Notikewin).

The Underfilled Foreland Basin is characterized by restricted marine and marginal marine mixed carbonate and clastic deposits (Nordegg-Rock Creek) sourced from the south and east; overlain by clastic dominated fluvial to marginal marine (shoreline, deltaic and estuarine) deposits of the Fernie (Nikinassin), Lower Mannville (Basal Quartz – Ellerslie, Ostrocod, Glauconitic, Spirit River (Wilrich, Falher and Notikewan) and Upper Mannville.Accommodation space increases to the north and northwest. Paleodrainage associated with the Underfilled Foreland Basin is characterized by fluvial and fluvial deltaic systems oriented dominantly from south and southeast towards north and northwest, splitting around paleotopographic highs associated with erosional remnants preserved from the migration of peripheral forebulge events. Shorelines are dominantly oriented east-west and are organized into falling stage, lowstand, transgressive, and highstand parasequences and parasequence sets. The shorelines are segmented along strike into compartments due to multiple point sources of sediment from the multiple S-N oriented fluvial and fluvial deltaic systems occurring along the length of the shorelines.

The transition between Underfilled and Overfilled Foreland Basin deposits is marked by a reorganization of paleodrainage and associated shoreline orientation. The Overfilled Foreland Basin is characterized by clastic dominated fluvial to marginal marine fluvial, deltaic, estuarine, shoreface and shelf deposits sourced from the west. Paleodrainage associated with the overfilled foreland basin is characterized by fluvial and fluvial deltaic systems oriented from west to east. Shorelines are oriented north-south, parallel to the length of the foreland basin.Key reservoir targets are associated with the Dunvegan fluvial, distributary and deltaic), Belly River (channels, shorefaces) and Cardium/Second White Specks).

The organzation of the WCSB-FB reservoirs into Underfilled vs Overfilled FB settings, and a detailed understanding of both the depositional environment and sequence stratigraphic framework are the first hierarchical steps in the better understanding of Deep Basin conventional and unconventional targets. According to Bhattacharya (2016), the source-to-sink (S2S) concept is focused on quantification of the various components of clastic sedimentary systems, from initial source sediment production areas, through the dispersal system, to deposition within a number of potential ultimate sedimentary sinks. During the Jurassic-Early Cretaceous (WCSB - Underfilled Foreland Basin), fluvial systems consisting of continental-scale low slope, axially drained rivers, formed the 40-m-deep channels in the Mannville Group in Canada. During times of maximum transgression (WCSB – Overfilled Foreland Basin) of the Cretaceous Seaway, such as the Turonian and Campanian, the western North American foreland basin was characterized by smaller-scale (typically 10-m deep), steeper gradient sand and gravel bedload rivers, dominated by transverse drainages in the rising Cordillera. This created a number of smaller river-delta S2S systems along the coast, such as the Dunvegan, Ferron, Frontier, Lance and Cardium formations.

Conventional (conglomerate shoreface) reservoirs were major exploration targets from their first discovery in the late 1970s until the advent of horizontal drilling in the Deep Basin in 2005. Primary porosity (3 to 8%) and permeability (1 to 50md Kmax) of the conglomeratic reservoirs are well within the conventional range of reservoir quality. Highest Kmax values are associated with bimodal to unimodal clast-supported, chert-pebble conglomerate facies.

In contrast, unconventional reservoirs are associated with lowstand to falling stage, low accommodation, pebbly chert sublitharenite and quartzose sandstone comprised of shoreface- to- wave dominated delta facies associations.Matrix permeability values are below the resolution of routine core analysis in these characteristically “tight” unconventional reservoirs, which are exploited almost exclusively through horizontal drilling and multi- stage frac completions. The Spirit River Group (Wilrich, Falher and Notikewin), commonly referred to as the “Wilrich” resource play are an excellent example. Reservoir attributes are interpreted to be the product of deposition on low profile, dissipative shoreface/delta fronts developed in a low accommodation setting. The reduced accommodation space results in commonly occurring incisions of shorefaces and delta front facies by fluvial and estuarine channels. Conglomeratic and coarse grained shoreface parasequences are products of deposition on steep profile, highly reflective shorefaces in high accommodation settings. In contrast, finer grained shoreface and delta front parasequences are products of deposition on low profile, dissipative shoreface/delta fronts in low accommodation settings.

Your Instructor

Brian A. Zaitlin & Thomas F. Moslow, CSPG
Brian A. Zaitlin & Thomas F. Moslow, CSPG

Brian A. Zaitlin is currently President and Owner of Zaitlin Geoconsulting Ltd, providing consulting services and applied training seminars to the oil and gas industry. Brian has >35 years of front-line exploration/exploitation, R&D and A&D experience, and has progressively worked as a Geologist, Explorationist, Technical Specialist, Technical and Exploration Advisor and Chief Geologist with a variety of E&P companies (e.g. Gulf, Esso, PanCanadian, Encana, Suncor and Enerplus Resources Fund, EOG Resources) and in Corporate Banking/Private Equity with the BMO A&D Advisory Group and Native American Resource Partners.

Brian’s focus is on both conventional and unconventional new play development throughout the Western Canada Sedimentary Basin, Rocky Mountain Basins, Appalachia and various international basins. His research interests lie in the understanding of siliciclastic fluvial, coastal and shallow-marine depositional systems and their preserved stratigraphy, and in applying this knowledge to reservoir characterization and modeling. He is the author of more than 100 peer-reviewed technical papers and oral presentations, and is the recipient of numerous awards including the CSUR Sproule Innovation and Achievement Award, CSPG Medal of Merit for best published paper, CSPG Tracks Award for Education, CSPG Ph.D. Thesis award, co-authored AAPG, SEPM and CSPG Best Paper/Oral Paper Awards, and was an AAPG Distinguished Lecturer.

Brian holds a BSc. (Geology) from Concordia (Loyola) University (1979), a MSc. (Geology) from University of Ottawa (1981), and a Ph.D. (Geology) from Queen’s (Kingston) University (1987). Brian is a registered Professional Geologist (APEGA), Certified Petroleum Geologist (AAPG-DPA) and a member of the AAPG, CSPG, CSUR, RMAG and SEPM.

Dr. Tom Moslow is an Adjunct Professor in the Department of Geosciences at the University of Calgary and a former Professor (1985–1994) at the University of Alberta and Louisiana State University (1983-87). In 1995 Tom was employed by Canadian Hunter Exploration as a Sr. Geological Advisor. He subsequently joined Ulster Petroleums as Chief Geologist in 1997 and was appointed Vice President, New Ventures and Technology. In 2000, Tom became a co-founder and principal of Midnight Oil & Gas Ltd. as Vice-President of Exploration which led to the creation of Daylight Energy Trust where he served as Vice President of Geology and Geophysics. He held executive positions in subsequent affiliated companies including Midnight Oil Exploration and Pace Oil and Gas Ltd. He retired from Pace at the end of 2011and in early 2012 formed Moslow Geoscience Consulting. Tom has won numerous awards and honours for his work and research on topics pertaining to the Triassic and Lower Cretaceous of the Deep Basin of Western Canada and tight gas/resource play geology in general. He has taught a variety of professional development courses focused on applied petroleum geology subjects in Canada, USA and South America. He has authored or co-authored over 75 publications in a variety of journals on topics mostly pertaining to clastic sedimentology, subsurface geology and reservoir architecture in unconventional clastic resource plays.