Developing a Sedimentologic and Stratigraphic Framework for the Falher G and Falher H Sandstone Successions in the Greater Kakwa area, Alberta 

John-Paul Zonneveld  | University of Alberta, Department of Earth & Atmospheric Sciences
11:30 am
Tuesday, January 23, 2018 | Marriott Hotel - Kensington Ballroom

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Abstract
John-Paul Zonneveld, Darren Tisdale, and Francois Legault

The Lower Cretaceous (Albian) Spirit River Formation comprises a complex association of clastic lithologies and represents deposition in a wide variety of depositional environments. This unit, which consists of the Notikewin, Falher and Wilrich members, has been the focus of hydrocarbon exploration in the Deep Basin of western Alberta for over four decades (eg. Jackson, 1984; Smith, 1984; Smith et al., 1984). The lowermost beds of the Spirit River Formation record a major marine incursion from the north, southwards towards the southernmost limits of the Western Canada Sedimentary Basin (Smith et al., 1984; Zonneveld and Moslow, 2004). The Spirit River Formation is approximately 350 metres in overall thickness and has been subdivided into a series of sandstone and conglomerate-dominated shingle-sets deposited in shallow marine depositional settings, with laterally equivalent heterolithic coastal plain deposits to the south / southeast and fine-grained strata deposited in offshore settings to the north (eg. Smith et al., 1984; Casas and Walker, 1997; Zonneveld and Moslow, 2004; Caddell and Moslow, 2004).

Initial (1970s-early 2000s) exploration interest in the Spirit River Formation focused on high permeability (~10 to >1000 md) / moderate porosity (~6-12%), unimodal to bimodal, clast-supported conglomerate intervals (eg. Smith et al., 1984; Moslow and Zonneveld, 2004; Zonneveld and Moslow, 2004). These horizons, although lucrative exploration targets, comprise only a small proportion (<1%) of the Spirit River Formation. Very fine-grained, fine-grained and medium-grained sandstone successions, although volumetrically much more significant, were avoided due to low porosity and very low permeabilities (Cant and Ethier, 1984), which rendered them non-commercial exploration targets using technology available at the time. Innovation over the last decade in drilling and completion technologies (including horizontal wells and multi-stage fracs) has turned these sandstone units into compelling exploration targets, particularly in areas with stacked, over-pressured, laterally extensive sandstone units.  Thus, recent attention has focused on moderate porosity (5-7% average) / low permeability (0.01-0.10 md) sandstone plays in the lower Falher / upper Wilrich interval (eg. Moslow and Ala, 2012; Bann and Ross, 2014a, 2014b; Fawcett, 20914; Newitt and Pedersen, 2015; 2016; Bann and Fawcett, 2016).

Conglomerate / sandstone units in the Spirit River Formation are informally referred to, from top to base, as the Notikewin Member, Falher A through F members, (Jackson, 1984).  Falher subunits were initially defined on the basis of the occurrence of clastic reservoir lithologies between regionally occurring coal layers.  Thus, some of the lettered units consist of single shingles or parasequences whereas others include several shingles or parasequences (i.e. parasequence sets). Some workers (eg. Smith et al., 1984; MacDonald et al., 1988; Zonneveld and Moslow, 2004) recognized lower Falher parasequence set (the Falher G and H) however industry practice over the past decade has been to refer to reservoir sandstone units in the lower Spirit River Formation as the ‘Wilrich play’ particularly in the absence of a regional (basin-wide) stratigraphic framework for Falher subunits. Complicating matters, it has recently been recognized that shale and siltstone successions in the Wilrich Member (sensu stricto) also comprise local exploration targets, rendering usage of the term ‘Wilrich’ for sandstone units problematic. Thus we advocate extending Falher letter nomenclature to sandstone units in the lower Spirit River Formation, to differentiate these reservoir units from lithologically distinct units in adjacent shale and siltstone successions (e.g. Zonneveld et al., 2017; Newitt, 2017).  This contribution focuses on the Falher G and H units in the greater Wapiti-Kakwa area of Alberta (T61-T68; R6-12W6). Both units consist of several discrete, regionally correlatable sandstone reservoir units however they contrast sharply in terms of lithological composition and, although both are excellent reservoir targets, the two units differ strongly in terms of ease of drilling (rate of penetration).

All available core and well logs were analyzed to develop a detailed sedimentologic / palaeographic model for the study interval. The lower Spirit River Formation was deposited within a shallow inland seaway in which major storms touched the sea floor in much of the basin. Depositional gradients were affected by both sediment delivery rates as well as structural influences related both to subsidence in the Peace River Arch area as well as movement in the thrust front and subsidence in the foredeep depocentre.

Shingles within the Falher H interval are dominated by quartzose, very fine-grained to fine-grained sandstone deposited in shoreface and wave-dominated deltaic settings.  Horizontal wells within this interval have, overall, moderate to high rates of penetration. The contact between the Falher H and the overlying Falher G interval is erosional in the study area and is interpreted as a coplanar regressive surface of erosion / transgressive surface of erosion. 

Similar to the Falher H, the Falher G consists of a series of sandstone bodies deposited in shoreface and fluvial to wave-dominated deltaic successions. Falher G sandstone beds differ strongly from Falher H sandstone beds in terms of their overall higher proportion of chert grains and granules and silica cements, resulting in a comparably abrasive lithology and significantly lower rates of penetration in horizontal wells. Higher lateral variability in sandstone composition reflects higher fluvial dominance / influence in the Falher G interval. A subtle change in shingle orientation between the Falher G and H intervals and a higher proportion of chert-dominated rock fragments and overall decrease in sediment sorting in the Falher G interval may reflect an interval of more active tectonism during deposition of the Falher G interval. 

Biography
  John-Paul Zonneveld is a Professor in the Department of Earth and Atmospheric Sciences at the
University of Alberta, curator of the University of Alberta drill core collection and SEPM Special
Publications Editor.  John-Paul has been with the University of Alberta for ten years.  Prior to this
John-Paul was a Research Geologist with the Geological Survey of Canada. 

John-Paul’s research is focused in the areas of sedimentology, stratigraphy, palaeoecology and
palaeontology. John-Paul’s research projects are typically multidisciplinary and commonly focus
on problems involving the interface between geological and biological system.  Current projects include:
mixed siliciclastic-carbonate depositional systems and reservoir controls in the Triassic of western
Canada (Montney, Doig, Halfway and Charlie Lake formations and their outcrop equivalents); reservoir
controls in shoreface and deltaic successions in the Fernie, Spirit River, Cardium and Dunvegan
formations of Alberta and British Columbia; the sedimentology, biostratigraphy and paleoecology of
Early to Middle Eocene successions in southwestern Wyoming; and the Paleogene to Quaternary
paleontology and sedimentology of Island Southeast Asia (focusing on Sumatra, Kalimantan, Sumba,
Bali and Timor).

ACKNOWLEDGEMENTS
John-Paul is grateful to Modern Resources for allowing him to present the results of this team project. Tom Moslow, Richard Harris, Dave Smith and Rob Sadownyk and the former Canadian Hunter Falher team are thanked for discussions on the depositional framework and resource potential of the Wilrich-Falher interval.

REFERENCES
Fawcett, M. 2016. The Wilrich Member, Alberta deep basin: an example of a topset-dominated delta deposited into a low-accommodation shallow sea. William C. Gussow Geoscience Conference 2016. Banff, Alberta, 5 p. 

Bann, K.L. and Ross, D.J.K. 2014. Facies analysis of the Lower Cretaceous Wilrich Member (Lower Falher) of the Spirit River Formation. Geoconvention 2014, Focus: adapt, refine, sustain Calgary, Alberta, 5 p. 

Bann, K.L. and Ross, D.J.K. 2014. Sedimentology and ichnology of the Lower Cretaceous Wilrich Member (Lower Falher) of the Spirit River Formation. Geoconvention 2014, Focus: adapt, refine, sustain Calgary, Alberta, 5 p. 

Cant, D.J. and Ethier, V.G. 1984. Lithology-dependant diagenetic control of reservoir properties of conglomerates, Falher Member, Elmworth Field, Alberta. AAPG Bulletin 68: 1044-1054
Caddell, E.M. and Moslow, T.F. 2004. Outcrop sedimentology and stratal architecture of the Lower Albian Falher C sub-member, Spirit River Formation, Bullmoose Mountain, northeastern British Columbia. Bulletin of Canadian Petroleum Geology 52: 4-22. 

Casas, J.E. and Walker, R.G. 1997. Sedimentology and depositional history of units C and D of the Falher Member, Spirit River Formation, west-central Alberta. Bulletin of Canadian Petroleum Geology 45: 218-238. 

Fawcett, M.D. 2014. Reservoir parameters in the Wilrich Member of the Spirit River Formation. Geoconvention 2014, Focus: adapt, refine, sustain, Calgary, Alberta, 1 p. 
Jackson, P.C. 1984. Paleogeography of the Lower Cretaceous Mannville Group of western Canada. In: Elmworth – case study of a deep basin gas field. J.A. Masters (ed). American Association of Petroleum Geologists, Memoir 38: 49-78. 

Macdonald, D.E., Langenberg, C.W., and Strobl, R.S. 1988. Cyclic marine sedimentation in the Lower Cretaceous Luscar Group and Spirit River Formation of the Alberta Foothills and Deep Basin: Sequences, Stratigraphy, Sedimentology: Surface and Subsurface. Canadian Society of Petroleum  Geologists Memoir 15: 143-154. 

Moslow, T.F. and Ala, D. 2012. Reservoir properties and sedimentary characteristics of the Falher G (i.e. Wilrich) Tight Gas Resource Play, Deep Basin, Alberta. Geoconvention 2012, Vision, Calgary, Alberta, 2p.

Moslow, T.F. and Zonneveld, J-P., 2004. Foreward – Marine conglomerate reservoirs: Cretaceous of western Canada and modern analogues. Bulletin of Canadian Petroleum Geology 52: 1-3. 

Newitt, J.D. and Pedersen, P.K. 2015. Depositional environments within the Wilrich member, Spirit River Formation – North central Alberta. Geoconvention 2015: New Horizons, Calgary, Alberta,  2 p. 

Newitt, J.D. and Pedersen, P.K. 2016. Contrasting reservoir properties for Albian Wilrich and Falher  shoreface sandstones, Spirit River Formation, west-central Alberta, Geoconvention 2015: optimizing Resources, Calgary, Alberta, 2 p.  

Smith, D.G., Zorn, C.E. and Sneider, R.M. 1984; The paleogeography of the Lower Cretaceous of Western Alberta and northeastern British Columbia in and adjacent to the Deep Basin of the Elmworth area. In: Elmworth – case study of a deep basin gas field. J.A. Masters (ed). American Association of Petroleum Geologists, Memoir 38: 79-114.

Smith, R. 1984. Gas preserves and production performance of the Elmworth/Wapiti area of the Deep Basin. In: Elmworth – case study of a deep basin gas field. J.A. Masters (ed). American Association of Petroleum Geologists, Memoir 38: 153-172.

Zonneveld, J.P., Moslow, T.F. 2004. Exploration potential of the Falher G shoreface conglomerate trend: evidence from outcrop. Bulletin of Canadian Petroleum Geology 52: 23-38.