Diagenesis and Petrographic Reservoir Characterization of the Mission Canyon Formation, Southeastern Saskatchewan

Diagenesis and Petrographic Reservoir Characterization of the Mission Canyon Formation, Southeastern Saskatchewan Congwei Ji 1 and Osman Salad Hersi 1 Information from this publication may be used if credit is given. It is recommended that reference to this publication be made in the following form: Ji, C. and Salad Hersi, O. (2016): Diagenesis and petrographic reservoir characterization of the Mission Canyon Formation, southeastern Saskatchewan; in Summary of Investigations 2016, Volume 1, Saskatchewan Geological Survey, Saskatchewan Ministry of the Economy, Miscellaneous Report 2016-4.1, Paper A-5, 16p. Abstract In southeastern Saskatchewan, the Mississippian Mission Canyon Formation was deposited on the northern platform margin of the Williston Basin and includes, from bottom to top, Tilston Beds, Alida Beds, Kisbey interval and Frobisher Beds. The formation is dominated by carbonate lithofacies; subordinate evaporites and sandstone lithofacies also occur within the formation. The lithologic properties and sedimentary structures of the formation indicate a depositional system of subtidal carbonate sand shoals to supratidal muddy carbonates and evaporites (Tilston, Alida and Frobisher beds) and localized sandy tidal creeks (Kisbey Sandstone). The depositional system developed on a ramp-type carbonate platform with a vertical stacking pattern controlled by relative sea-level fluctuations. The formation preserves a complex diagenetic history that affects the reservoir qualities of the various stratigraphic intervals of the formation. In this study, petrographic examination of cores and thin sections from the formation identified the diagenetic features in the rocks, and their paragenetic sequence and effects on the reservoir quality of the strata. Four major diagenetic processes profoundly affected porosity development of the Mission Canyon Formation. Cementation, compaction, dolomitization and dissolution were active throughout the evolution of the formation. Different degrees of porosity-destruction and porosity-enhancement features result in porosity and permeability differences among the lithofacies of the Mission Canyon Formation. The Tilston Beds and Kisbey interval show good porosity and permeability, the Alida Beds and Frobisher Beds exhibit moderate porosity and permeability. The tidal channel siliciclastics and carbonate sand shoal show good porosity and permeability. Keywords: Mission Canyon Formation, southeastern Saskatchewan, Alida Beds, Kisbey interval, Frobisher Beds, Tilston Beds, porosity, diagenesis, reservoir quality, petrography, dolomitization, calcite cement 1. Introduction The Mississippian strata of southern Saskatchewan and adjacent North Dakota and Montana are prolific hydrocarbon producers that have been studied for many decades (Yurkowski, 2013). These strata were deposited on the northern flanks of the Williston Basin, a subcircular basin with a depocentre in North Dakota (Figure 1). The Madison Group forms the bulk of the Mississippian succession and consists of the Lodgepole, Mission Canyon and Charles formations, in ascending order (Figure 2). The Mission Canyon Formation of southeastern Saskatchewan consists of four stratigraphic units: Tilston Beds, Alida Beds, Kisbey interval and Frobisher Beds, in ascending stratigraphic order (Marsh, 2006; Nickel and Yang, 2011; Ji and Salad Hersi, 2014; Ji, 2016; Figure 2). The Mississippian Mission Canyon Formation of the Williston Basin comprises a mixed carbonate-siliciclastic-evaporitic succession (Figure 2). Carbonate lithology prevails in these rocks in regions both north and south of the Canada–USA border. Thinner, laterally extensive siliciclastic and evaporitic strata are also present. The stratigraphic nomenclature and interpretation of the depositional environments of these strata have been addressed by different researchers over the years (Thomas, 1954; Fuller, 1956; Edie, 1958; Fuzesy, 1960; Roberts, 1966; Kent, 1987, 2004, 2007; Kent et al., 1988; Witter, 1988; Legault, 1999; Howard, 2000; Halabura, 2006). Oil accumulations occur in the porous carbonate and subordinate sandstone units of the Mission Canyon Formation, and have been truncated and sealed by the pre- Mesozoic unconformity. 1 University of Regina, Department of Geology, 3737 Wascana Parkway, Regina, SK S4S 0A2 Although the Saskatchewan Ministry of the Economy has exercised all reasonable care in the compilation, interpretation and production of this product, it is not possible to ensure total accuracy, and all persons who rely on the information contained herein do so at their own risk. The Saskatchewan Ministry of the Economy and the Government of Saskatchewan do not accept liability for any errors, omissions or inaccuracies that may be included in, or derived from, this product. Saskatchewan Geological Survey 1 Summary of Investigations 2016, Volume 1 Figure 1 – A) Location map showing the study area in southeastern Saskatchewan, configuration of the Williston Basin, and the location of the Sweetgrass Arch, Montana Trough and Antler foreland basin (modified from Nimegeers, 2006). B) Map showing the distribution of the wells examined in the study area. Numbered well locations are keyed to Table 1. Saskatchewan Geological Survey 2 Summary of Investigations 2016, Volume 1 Figure 2 – Stratigraphic chart of Mississippian strata in southeastern Saskatchewan (modified from Nimegeers, 2006). The Williston Basin in Saskatchewan, North Dakota and Montana is a major intracratonic basin (Fowler and Nisbet, 1985; Kent and Christopher, 1994). The basin was created by uplift and erosion of the cratonic arches surrounding the basin in periods between transgressive-regressive cycles, as a result of differential subsidence of the basin during the cycles (Porter et al., 1982). Four major transgression and regression events occurred across the basin from the Cambrian to the Jurassic (Wilson, 1975). Mississippian sediments evolved as a transgressive-regressive cycle equivalent to the upper part of Sloss’s (1963) Kaskaskia Supersequence (Wilson, 1975). The Mississippian Madison Group of the Williston Basin in southern Saskatchewan contains a 400 to 700 m thick section of mainly carbonate succession with minor evaporite and sandstone sediments (Wegelin, 1984). The sedimentation pattern of the group is typical of a major upward-shoaling sequence, deposited as a thick basin-ward migrating wedge of sediments (Lake, 1991). Superimposed on this sequence are smaller-scale transgressive-regressive parasequences, which are interpreted to be the result of sea-level fluctuations (Wilson, 1975; Ji, 2016). Sediments of the Saskatchewan Geological Survey 3 Summary of Investigations 2016, Volume 1 Mississippian Mission Canyon Formation were deposited in a relatively stable, broad, and shallow epicontinental sea in a periodically restricted environment (Richards, 1989; Rott and Qing, 2005). Several studies of the Mission Canyon Formation in North Dakota and Montana have emphasized the occurrence of solution-collapse breccias and their effect on porosity, permeability and hydrocarbon production (Roberts, 1966; Sando, 1974, 1988; Gargallo-Quinones, 1985). Studies of the depositional and diagenetic history of the Mission Canyon Formation include Lindsay and Kendall (1980); Lindsay (1982); Lindsay and Roth (1982); Vice (1988, 1993); Vice and Utgaard (1989, 1996); Smith (1991); and Smith and Dorobek (1993a, 1993b). Vice et al. (2000) established a paragenetic sequence for the Mission Canyon Formation in south-central Montana and northern Wyoming. Mundy and Roulston (1998) studied the diagenesis and porosity development within the Alida Beds in southeastern Saskatchewan. Despite the many studies addressing the lithologic, stratigraphic and diagenetic aspects of the Mission Canyon Formation in the northern Williston Basin, more detailed work on the diagenetic evolution of the formation and reservoir characterization is required. The present study is part of an M.Sc. thesis project by the senior author (Ji, 2016) to interpret the diagenetic features preserved in the various units of the formation, and establish their paragenetic sequence, diagenetic realms and effects on the reservoir qualities of the various lithologic units of the formation. 2. Methodology The study area is within Townships 1 to 8 and Ranges 30W1 to 6W2 in southeastern Saskatchewan (Figure 1). Cores from twenty-five wells and drill cuttings from four wells containing the Mission Canyon Formation were examined (Figure 1, Table 1). Eighty-five thin sections from nine of these cores were examined, and the microfacies and diagenetic properties of the rocks identified. The porosity and reservoir quality study is based on integration of petrographic attributes from core samples and thin sections with porosity and permeability data obtained from geoSCOUT for a few select wells (wells 9, 11, 13, 16 and 24 in Table 1) from the various strata of the Mission Canyon Formation. Table 1 – List of wells studied in southeastern Saskatchewan, of which 25 have core available for examination (wells 1 to 25) and 4 have only drill cuttings available (wells 26 to 29). Well Number Well ID Licence Cored Interval Drill Cutting Number (m) Interval (m) 1 101/04-09-008-06W2 67B002 1228.0 to 1243.6 2 111/13-13-008-06W2 87I040 1181.0 to 1199.0 3 101/03-08-001-06W2 57D025 1759.8 to 1891.0 4 121/03-32-007-05W2 84A107 1224.0 to 1241.4 5 101/03-26-004-05W2 55J092 1374.0 to 1483.2 6 141/03-24-007-04W2 93H085 1208.0 to 1226.8 7 141/04-22-007-03W2 08J439 1195.0 to 1213.3 8 101/06-01-006-03W2

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