POOR IMAGE DUE TO ORIGINAL DOCUMENT QUALITY -JC.plt, 5 - ot/-oI General Geology of Lower Cretaceous Heavy • Oil Accumulations In Western Canada By L W. VIGRASS* (Heavy Oil Semillur, The Petrolell1n Society of C.l.~I., Calgary. llIay .5, 1.965) ABSTRACT The oil throughout the belt is asphaltic and contain.'3Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021 large amounts of sulphur. nitrogen and oxygen. Gra­ Lower Cretaceous sand reservoirs contain about 750 billion barrels of "lscous, heavy oil along a broad arcuate vities range from 6° to 18° API and viscosities from belt that extends from northwestern Alberta into west­ several hundred to several million centipoise at GO°F, central Saskatchewan_ The heavy on is pooled in the Studies of sulphur isotopes, trace metal content and Mannville Group and, in a gross sense. occurs in a marine­ continental transition facies. The accumulation at Peace high molecular weight compounds show a fundamen­ River is in a regional onlap feature. The accumulations in tal similarity between Athabasca, Bonn.yville und the Athabasca-Llo}'dminster region occur across the Lloydminster crude oils. crest and on the southwest flank of a regional anticlinal feature associated with the solution of salt from Middle The change in character of the oil with geographic Devonian beds. These re~ional features had already position and depth is not ' ...·ell documented, but oils formed by the end of Early Cretaceous time. from deeper reservoirs at the south end of the bell Chemical and physical I)rOperties of oils from differ­ are more paraffinic, have higher API gravities and ent accumulations show that they belong to a single oil s:,.,stem and suggest a common mode of origin. The Atha­ are less viscous than those from the shallow reserVOil'9 basca oil is youn~ and immature and not e... aporated, al­ at the north end. These changes are reflected in the tered or polymerized. The oil is not escaped and re-de­ producibility of the oil; pools of the Lloydminstel' posited Deyonian oil. The most tenable working hypo­ region have yielded considerable oil by conventional thesis is that h:rdrocarbons moved out of sediments in the deep basin in micellar solution in compaction waters. oilfield production methods, whereas the major nc­ The h:rdrocarbons were deposited as heav}· asphaltic oil cumulations to the north, here referred to as deposits, where physical-chemical conditions were suitable_ Early­ to date have not :yielded commercial oil. formed stratigraphic and structural "traps'· ser...ed as loci of deposition for the hea..'y oil. Since deposition, and In this paper, we will consider first the regional ~o ...erned b}' buo}'ancy and capillarity. there has been stratigraph)" and depositional framework of the Low­ some adjustment in position of the oil in the traps. er Cretaceous Series, second the reservoir geometry and fluid distribution of individual accumulations, INTRODUCTION and third the possible mode of genesis of the oiL HIS paper concerns the geology of the main belt T of Lower Cretaceous heav.y oil accumulations in STRATIGRAPHY \Ve~tern Canada, It is hoped that the regional ap­ The Lower Cretaceous Series of the vVestern Can­ proach that is used will improve our understanding ada basin comprises a sequence of interbedded sand­ of the individual accumulations and will aid in their stones and shales that rests unconformably on eroded exploitation. Jurassic, Triassic and Paleozoic strata and is conform­ The main Lower Cl'etaeeous heavy oil belt extends abljr overlain b)r Upper CretaceoliS rocks. The lower. as a GOO-mile arc from Peace River in northwestern sandier part of the Series, referred to the Mannville Alberta to Llo~!dminster in western Saskatchewan Group in the Central Plains area, contains the heavy I Figm·e 1). The total amount of heavy oil reservoired oil accumulations (Figure 2). The rocks of the Mann­ in the sandstones of the belt is immense, totalling at ville Group and their later31 equivalents are com­ lease 750 billion barrels of oil-in-place. About 95 pel' monly 500 to 600 feet thic.k in the Plain:;; area and cent of the knm't'n oil oc.curs in the Athabasca, Peace thick"en weshvard into the Alberta Foothills and into River, \Vabasca and Cold Lake deposits. Oil-sand de­ a tectonic basin west of Peace River. The i\lannville posits at Buffalo Head Hills. Bad Rapids and Loon sequence is overlain conformably by dominantly ma­ River (PO\II", et ai., 1963, Figure 3) are considered to rine shaly rocks of the Colorado Group. be too small to be of economic significance and are Rudkin (1965) has divided the Mannville Group not discllssed in this report. into two map units that have time-rock significance The accumulations along the belt, because they oc­ (Figure 2, Column 6). The Lower Mannville is a cur in the lower part of the Lower Cretaceolls se­ basal deposit composed of continental sand:i over much quence and because of the nature of the oil, are con­ of 'Vestern Canada, but it grades into marine shale in sidered to belong to a single oil province or system. extreme northern Alberta. The main heavy oil accum­ ulations in LO\,;,er l\oIannvilIe rocks occur in the Peace River, \Vabasca and Athabasca areas. Strictly speak­ '''Westel'n ResojlTCes C011sultants Ltd., Calgary, A..l­ ing, oil deposits in the Bluesky and vVabiskaw tt'ClnS­ berta. gTessive sands should be referred to the Upper Mann­ ,rille, but, in this report, as a matter of convenience, (Formerly with Imperial Oil Limited, Calgary). they are included with the Lower Mannville deposit~. 168 The Journal of Canadian Petroleum POOR IMAGE DUE TO ORIGINAL DOCUMENT QUALITY I .,j -----fi- --ii------5BO N ] i \ 1 " ! ....••.~.:,..:_.~..~.'J,< i I ,,;.:." I j -: ~ tEt~pEJr(_r,\:p SCA .-."~.:-:_:.''.c.:.~,;;~-.:~.'.:.:,._: _:.:.·.;.:;.:t.~ 1.~.:,',::~HZ~f\,A wtro .' ... ..:.,·:':·.• .•... .. :ASCA DEPOSIT !, i Z,,'c.-;-i~·,.,.~. PSIT" ,.' " c.. "".'" .:.< _ B. C. I ti}~f~~~;:!,;;,:R:;'i>:\ <',~i;:::~{;;~. ~\ SAsK f ---. """>.J ,'", ::;:1 I .~I i i ALTA ":}A COLD LAKE ,.:';,:1 DEPOSIT . • OIL FIELDS HAROLD LAKE""':.! . Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021 I </.. OIL DEPOSITS BONNYVILLE- .;}\ ~ \ '0 WESTERN CANADA • EDMONTON i VERMILION· 0 " LLOYDMINSTER '.: ~OWER CRETACEOUS BAXTER LAKE~ 1~ ··0 FIELDS HEAVY OIL ACCUMULATIONS WAINWRIGHT" ~CHAUVIN , " HUGHENDON- 100 MILES i 52 0 1'1-------+1-----­ i Figure L MAP The Upper Mannville unit commonly consists of in­ PEACE ATHABASCA COLD LAKE LLOYD- terbedded marine and non-marine sands and shales, RIVER -WABASCA MINSTER UNIT UPPER ,sHAFTES· but in northwestern Alberta the unit consists of CRETACEOUS BURY LAI!ICHE ~~~~ :?.LORAD C' ---- f-- marine shales of the Spirit River FormatioD_ A thick fM. FM. ~,::p GROUP GROUP ,-O~~?" PEACE PEliCAN tongue of marine shale (Clearwater Formation) ex­ 0' RIVER JOLIFOU e tends eastward into the Athabasca area below sandy fM ~ Grand Rapids beds. Correlation of Upper Mannville GRAND - "A- UNIT = RAPID,s , ,sPIRIT ~ 'B~ is WASEC,O" ",,'l,.,$:' rocks to the southeast is difficult, but in the Cold RIVER FM. UNIT LOWER • - '" SP ..~~y = ~"'~.J:,."" Lake area a thick sandy depositional cycle (Mannville CRETACEOUS FM. CLEAf!.- • .... 5-~f:"L ~ V/A.1Ef.. ~ "C-UNIT ~ FM LL YO"'" -#' "c" of this paper) appears to be approximately cor­ BluE,sKY , relative with the Clearwater Formation. In the Lloyd­ FM .P".I~"""" ~~ ~ & ...."" minster region, tongues of marine sedimentary rock ~ GE~t;'lNG MCMURRAY 'D-UNIT ---- :: DIN'" O~'''' g FM. g -<' occur in the lower part of the Upper :Mannville unit. m C.."C#IN Most of the Upper Mannville oil' occurs in the Grand M1S,sISSIPPIAN DEVONIAN DEVONIAN DEVONIAN ..' UNDERLYING PERMIAN _BEAVERHILL • BEAVERHill WOODBEND II. Rapids Formation at \Vabasca, in the thick "G" unit BEDS &. JURASSIC TO WABAMUN &. WOODBEND WINTERBURN c- and younger Mannville sands at Cold Lake, and in DOllOCCURIiHICE the Sparky and General Petroleums sands of the Figure 2"-Hca1Jy oil oCC1t7""enCes in LCJwel" Cretaceous Lloydminster region (Figure 2). ?"oc'(, units of IVeste7'71. Canada. :-:"~:~ ..:- .. The Lo\ver Mannville unit was deposited on an , r····~ _erosional surface of considerable relief that truncated WESTERN CANADA BASIN the J urassie and older strata of the Western Canada LOWER MANNVILLE basin. Continental, probably fluviatile, sedimentation DEPOSITIONAL FRAMEWORK persisted over much of the Western Canada basin dur­ ing deposition of the Lower IVlannville unit, but an Arctic or Boreal sea layover part of northern Alberta. ~OOMJLlS At the end of the depositional episode, the sea trans­ gressed southward and eastward (Figw"e 3) and re­ worked the Bullhead and McMurray sands of north­ ,,-. ern Alberta into the glauconitic Bluesky and Wabis­ ka,v sands. Topogl'aph}Y on the sub-Cretaceous erosion- ,; al surface had a considerable effect on the deposition -\ . of the Lower Mannville (Rudkin, 1965), and the ~­ "highest hills on this surface were not completely on­ ''\ lapped by Lower Mannville sediments (Figure 3). B.C. The coarser clastic material was derived both from a western Cordilleran region and from an eastern Ca­ ------" nadian Shield region (Glaister, 1959, p. 620; Mellon, -'-.- 1956) . Figu7"e 9. Technology, October-December, 1965, Monfreol 169 POOR IMAGE DUE TO ORIGINAL DOCUMENT QUALITY :Marine transgression ",vas more extensive during sands over a large part of the '''estern Canada basin deposition of the Upper :Mannville unit_ A Boreal sea had a southwestern provenance (Glaister, 1959, pp. persisted over northeastern British Columbia and G33-G3G; Williams et ai., 19G2). Chemical data strong­ northwestern Alberta_ The northern sea advanced in­ ly suggest, hm\'ever, that some of the Upper Mann­ termittently sQutheash·;,rard into the Athabasca, Cold ville sands in eastern Alberta and western Saslmtche­ Lake and Lloydminster regions and may have joined wan were derived from the northeast (Cameron, 1965, at times with a sea transgressing from the south pp.