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-JC.plt, 5 - ot/-oI General Geology of Lower Heavy • Oil Accumulations In Western

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 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 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 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 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 beds. These re~ional features had already position and depth is not ' ...·ell documented, but oils formed by the end of 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 \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 that rests unconformably on eroded exploitation. , and 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 in northwestern sandier part of the Series, referred to the Mannville Alberta to Llo~!dminster in western 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 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 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 . 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 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 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 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 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 () 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 _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 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, 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

: ",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 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. 75-771. (FiglO"e 4). There is evidence that Upper Mannville Following deposition of the Upper Mannville unit, there was widespread transg'l"ession of an epicon­ WESTERN CANADA BASiN tinental sea. The dominantl~l shaly rocks assigned to UPPER MANNVILLE the Colorado Group and equivalent units were de­ DEPOSITIONAL FRAMEWORK posited over much of the \Vesterll Canada basin.

PEACE RlVER DEPOSIT loa "'ILEl Heavy oil of the Peace River depol)it occur~ in sands of the b3.sal Cretaceous and the over­ , lying ElueskJr Formation (Figure 2). The Bullhelld­

, Bluesky reservoir unit rests unconformably on trun­Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021 " cated JLll·a~sic, Permi2.n and Mississippian strata and is conformably overlain by Spirit River shales. In the ,,-icinity of the Peace River deposit there is a gen­ \ eral northeast"'al"d thinning of the reservoir unit ,, from 450 feet to a feather edge in a distance of 100 Be , miles (Figure 5). Irregularities of the isopach pat­ tern result from vale-and-cuesta topography on the ---- underlying unconformable surface, In the northwest­ ern and eastern part of the map-area of Figure 5, the Spirit River shales onlap the reservoir sands to , ",--~~~~------, rest directly on a ridge of Mississippian rocks. The , ,zl - PEACE RIVER DEPOSIT heavy are more continuous and richer eust . 6~ ~. ALBERTA of the town of Peace River than they are to the '~i V /J'. ISOPACH OF BULLHEAD north, ,";est and south. The variation in oil content of the Bullhead-Bluesky unit, shown h)' the closeness of .. )1' ",i/.. o' PLUS BLUESKY stippling on FiglO'es 5 and 6, appears to result from r (v L/-:; J INTERVAL· 150 Ff completeness or perfection of pinchout of the reser­ .\ ';or .. .. /,' . OON,"O' voir unit, from structural position relative to the '\~(\----=1 \. ."-... :10 MILES pinchout edge and from reservoir ((uality of the Bull­ --. '·')1' C_ PEACERJV~~i·'·:.J.;;:"- __ head-Bluesky unit. North of the "Main Heavy Oil De­ posit" of Figures 5 and 6, the sand pinchout is in­ .~;". *_~:~~M-' . -HE~~~Oil '"")<.i\~'. .' J[l'7 . 2" D~. complete and there is a :mggestion of updip lealmge . ':;;;'~. '" ~ C"q ~ .\ ... or spillage of oil into the smaller Bullhead-Hluesley ,. "k7 '::), -""'" .' . deposits at Buffalo Head Hills (Pow et at., 1963, Fig­ (.~C~,~ '''"~) ure 3). The discontinuous oil sands with high wnter ,"<:::. \iX'" '. .0, saturation that lie south and southeast of the town ·\~C~<::.~Jo '--o:;l\. '0 \p-7(.",l.c.,.,"" en. of Peace River are down the regional dip from the , 1\- .',\ ,,-/. c:. U (~")t-...... ~. '-;I ..~ .' \ " •• Cl, • _ ~'7"-""':::' r:.J "Main Deposit" (Figll?'e 6). The richness of the oil ~ Il~1 ~, I 71 ... 1"1 n r t'J"1 ,I • deposit is also controlled by the .sand-shale ratio of R~W5/.' 0:25 ••0 R15 the reservoir unit and the porositr of the sands. FiguTe 5_ An onlap trap appears to be the main control of oil accumulation in the Feace River deposit. The for­ mation of this trap was completed in Ear!)' Cretaceolls time with the deposition of the overlying shaly Spirit River bed:;. The reservoir unit has dipped west or southwest since the trap was formed.

ATHABASCA DEPOSIT The Athabasca deposit contains some 5GO to G2G bil­ lion barrels of heavy oil (Stewart, 19G3; Pow, et al., 1963). making it the largest of the accumulations in terrns of oil-in-place. The oil occurs in sands of the basal Cretaceous \Vabiskaw-McMurruy reservoiL' unit, 'which lies unconformably on De\'onian beds and is conformab!). overlain by the shaly Clearwater Forma­ tion (Figure 2). The gross thickness of the reservoir unit, genera:I~' less than 300 feet, is largely deter­ mined b,}' the form of the sub-CretaceoLis unconfor­ mity as described in detail by Stewart (l9G3) and by :Mal"tin and Jamin (1963). At least in part of the area, Figure 6. the sands in the IO'wer part of the reservoir unit are

170 The Journal of Canadian Petroleum POOR IMAGE DUE TO ORIGINAL DOCUMENT QUALITY

fluvial or deltaic and are sporadically distributed. with poor lateral continuity_ Sands in the upper part of the \Vabiskaw-McMurray unit were deposited in brackish 1.10 to marine waters (Mellon and Wall, 1956), and in­ r. dividual sand bodies may be more widespread_ Wabi­ INTERVAL ·100 H. i. • CONTROL skaw-Mcl\iurray sands extend beyond the limits of ~. the deposit, although the unit appears to be replaced 3D MILES by marine shale to the north and sparse control sug­ , gests that the unit thins and becomes shalier south of .1 Township 78. The reservoir unit thins westward and, at least Iocall}r. Rinches out against an erosional high developed on Woodbend-Winterburn rocks along the west edge of the oil deposit (see Figure 8)_ The reser­ voir unit thins toward the eastern edge of the depos­ it but does not pinch out and, along the Clearwater river, water-bearing sands occur updip from oil sands. An oil-water contact along the southeast edge of the deposit is defined reasonably well by drill holes (Stew­ Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021 art, 1963, pp_ 21-25)_ The structure on top of the Wabiskaw-McMurray •• "" " res~rvoir unit shows that the Athabasca deposit lies across a domal feature some 150 miles long by 60 miles wide (Figure 7). There is about 200 feet of ,. reversal of .regional dip from the crest of the high (, into a narrow syncline that lies along the Athabasca -I i'iver. The oil deposit coincides reasonably well ,vith " the domal feature, but a tenth of the area of the de­ posit, and considerably more than a tenth of the oH­ Dall DEPOSIT " RESTO REO B " in-place, lies in the trough or on the eastern limb of the bounding syncline. A ___[ ':ONTACTS t15oo,-_~k:Plosj::i lUoo The general relationship of the reservoir unit to :'-:". the sub-Cretaceous and to the structure :,.- ., . of the older rocka is shown on Structure Section A-B (Figure 8; location shown on Figures 7, 9 and 10). ~'~:~{f~~: Deep well control on and adjacent to this section ~E'" LEVEL ~EA lEVEl r.} ~~',:, ~;._ shows that the strong reversal of regional dip that , is apparent on the top of the Wabiskaw-McJl[urray ..

reservoir unit also affects Paleozoic strata. The 3D MILES trough of the narrow syncline in the Cretaceous is apparent on the Watt ilIountain or Elk Point top and ATHABASCA DEPOSIT appears to extend to the basement. l\'1uch STRUCTURE SECTION A-B of the structure in the upper Paleozoic beds, however, Figzu'e 8. is associated with northeastward thinning of the Up­ per Evaporite of the Elk Point, probably the result ATHABASCA DEPOSIT of the solution of salt. The broad anticline on the '\Vatt Mountain is formed where the Upper Evaporite STRUCTURE ON TOP OF ELK POINT begins its northeashvard thinning, and the synclinal INTERVAl.100 FT. trough occurs where the thinning is complete. The • CONTROL crest of the dome on the Wabiskaw-McMurray reser­ voir unit is west of tlie anticline on the Elk Point top 30 MILES and coincides with a high on the unconformity. This occurs because the reservoir unit, the basal sandy por­ tion of the Lower Cretaceous above the unconformity, is a time transgressive rock unit as pointed out by . Carrigy and Zamora (1960). A structural map on the top of the (Watt Mountain) shows that a sharp structural low corresponds in plan with the low on the top of the Wabiskaw-McMurray beds (Figure 9)_ A broad anti­ cline is parallel to this low, but it lies some 15 miles east of the high on the reservoir unit_ An interpreta­ tion of the present western limit of Elk Point salt solu­

tioD is shown on Figure 9_ ';,' -. If one could assume that the upper beds of the Figure 9, Wabiskaw-McMurray unit were deposited synchron­ Cretaceous time_ \Ve have shown that this assumption ously as a flat and level surface and that there has is not completely valid, but, on the regional scale used, been no differential compaction of the Lower Mann­ the isopach map approximates paleostructure, with ville beds since deposition, then an isopach from the the thicks representing structural lows and the thins top of the Wabiskaw to the Elk Point would repre­ representing highs. 'rhe isopach or paleostructure map sent a structure map of the Elk Point during Early shows that the anticline-s)'llcline pair on the Elk

Technology, October-December, 1965, Montreal 171 POOR IMAGE DUE TO ORIGINAL DOCUMENT QUALITY

P:\I 1:(1 II I I II ATHABASCA DEPOSIT ".,f\;\ ( iISOPACH. TOP WABISKAW • MCMURRAY \~' , "TO ELK POINT 'I~~ 1:' lNrE~YAl 100 fT ~ '\'\\\\ \\\. i/') -='JO MIlES '~\\\,. '~i (~'B "" , ~ .. -" "j\J \ '\ ( .. ----. OIL • \ . ~~ \ DEPOSIT: ,., . \'~ ,. ;,< '00, I I\ \\."1 r"$>\ I A, ~'\ ('0 -~ \!~ \~,\\" II~ \,'r \ .,1M', \ ' ,"" a Figm'c II. '''I J} II\I JL.hu,..ULUu..

• '.. , " -. '0 • , Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021

FigllJ'c 10

Point top was already present during Early Cretace­ lation_ Thick reservoir sands continue into the struc­ ous time (FigUT6 10). There has been post-Early Cl'e­ tural low area east of lhe major accumula.tion, but are tC!.ceolls deepening of the synclinal trough, but appar­ water-loaded there. Only those wells that penetrate ently there has been no weshvard shifting of the syn­ to Mannville "C" and serve to outline the oil accumula­ cline since Earl}" Cretaceous time as one might ex­ tion are shown on Figure 11 .. there are mllIlJ" other pect if there had been continuing dmvndip solution of wells that penetrate the Mannville top that were used salt. Thickening of the basal Cretaceous sand unit as structural control. into the hough suggests, but does not prove, that structural subsidence accompanied deposition of the H~~A"Y l'€SelTOil' unit. OIL FIELDS In ::;umrnar~", the \1ilabiskaw-l\icMurray reser\'oir Heavy oil in the conventional fields of the Bonny­ unit at Athabasca has the form of a dome, partly of ville and Lloydminster regions occurs mainly in the structural and partly of ::stratigraphic origin. The Upper .Mannville unit, with the bulk of the oil pooled dome had already formed when the Clearwater shale in the Sparky and General Petroleums members of ,vas deposited, but the amplitude of the structural fea­ the Lloydminster region (Figures 1-4). Combination ture has increased since Earl~{ Cretaceous time. A sig­ structural-stratigraphic traps are common. Many ac.­ nificant part of the Athabasca oil deposit lies outside cumulations are on noses or structural terraces which the dome in the trough and on the northeast limb of may represent compaction features over unconformity a syncline that is associated with salt solution from highs. The reservoir sands are winnowed, permeable the Devonian Elk Point Group, and oil-bearing over the structural highs and are ­ d}", impermeable and water-bearing in the lows. Traps also result from updip interfingering of gand with ,\VABASCA DEPOSIT shale. The oil-in-place in the conventional fields is Heavy oil in the \Vabasca deposit, situated south­ small ,..,.hen compared to the oil deposits fadher north. west and downdip fl·om Athabasca (Figu're 1), oc­ curs in both Lower and Upper Mannville units. \Vell control is scattered, but there is a suggestion that REGIONAL CONTROL OF ACCUMULATIONS IN THE the oil in the \Vabiskaw-McMunway sands occurs in ATHABASCA - LLOYDMINSTER REGION stratigraphic traps and that the oil in the Grand Rap­ There is evidence that the Lower Cretaceous henv.',' ids sands is trapped in compaction structures above oil occurrences in eastern Alberta and western Sask­ erosional highs on the unconformity. atchewan are related to an ancient regional structural feature. The isopach map of FignJ'e 12 again approxi­ COLD LAKE DEPOSIT m.ates paleostructure of the Elk Point top at the end of Mannville deposition. The pattern of thins und The sands that contain the hea,,)" oil at Cold Lake thicks reveals an ancient high trend and a pail'ed low are mainly in the Upper Mannville unit (Figw'e 2). trend that extends some 400 miles from north of The bulk of the oil is in the Mannville "C" unit, a Athabasca to southeast of Lloydminster. The present depositional cycle composed largely of nearshore ma­ northeastern edge of the Upper Elk Point or Prairie rine sand that Occurs 300 to 450 feet below the Mann­ salt lies close to the trough of the ancient synclinnl ville top. Significantly large amounts of oil are pooled feature, and the most obvious inLerpretation is that in )roungel' sands and some of these are of continental the large-scale feature resulted from salt solution that origin. occurred prior to the end of Mannville deposition. The main oil deposit at Cold Lake occurs on a large The main Cold Lake depo::iit is situated on the c.rest structural high feature in Mannville beds (Figure of the anticlinal feature, and the Athabasca depo~it 11) that coincides with a high on the eroded surface lies across it. The \Vubasca deposit and the conven­ of PaleOZOic roel(s. Sporadic accumulations with more tional heavy oil fields of the Bonnyville and Lloyd~ than 30 feet of oil-bearing sand occur on structural minster regions lie along the ,vest flank of the ancient highs southwest and do\\rndip from the major accumu- structural high feature.

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T.I~1r.--,--,--::c------j stability of abundant porphyrins (Hodgson, 1954), \\'\C...... i ATHABASCA -llOYDMINSTER REGION and the thermal instability of abundant organic sul­ phur compounds in the Athabasca crude (see Cole­ '''~Lt\ I ISOPACH· MANNVIlLE TOP TO ~ man et al., 1953). Based on general chemical composi­ \\ ..\% ...J,mo"" ELK POINT TOP tion and trace metal content, Montgomery (1951) and Hodgson (1954) showed that it is improbable that the :::,:j\~-' --:~~'- Athabasca and other Lower Cretaceous oils were de­ rived from Devonian oils. Thode et al. (1958, p. 2636) state: "The distribution of the sulphur. isotopes in Al­ berta crude oils seems to preclude the possibility of Devonian origin of the :McMurray oil sands." ',,"ork­ :~i \\\~~~\\,\;:~<::: ?~.,.\ ers at Gulf Research and Development Co. showed \\ that sulphonation of a Lloydminster crude oil resulted "I EDMONT\O\\'.. "'~.,:- :. .I\ ,l, "0" - UPDIP EDGE OF in an oil.which was superficially and chemically simi­ Td' • .. ~ ~..... _ "_!..--"" PRAIRIE SALT ::: u '" ':'. 0;:. ... " ...... Q 'j. Q" .. j OIL FIELDS' lar to Athabasca oil, whereas the same treatment of a Devonian oil failed to produce this similarity (Shray­ ,., \ \ '\ '. : ; '" ....' .. er et al., 1960). These chemical studies render unten­ :!d..TA\. - I• SASK. · ....: \ \'-...! .'. able Hypotheses 1 and 4, because these involve tne ~~.. ,",:" Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021 :: . "''--••",.--'-••&"---;.",••;-''',T.",-::::'"t,,,,,"-'''-''WJ M. alteration of light paraffinic oil to heavy asphaltic oil and because Hypothesis 1 presupposes a Devonian FigUTC 12: source. ','

The in situ ongm (Hypothesis 2) was proposed . ·' ,. GENESIS OF THE OIL originally to explain the interpretation of early work­

" .- 'Varkel's have advanced .five main hypotheses re­ ers that the individual grains in the Athabasca oil · ,~ :~ garding the source and accumulation of the Atha­ sands are separated by bitumen. Exhaustive studies " of the Athabasca material have shown that there is .~ basca.heavy oil: " grain-to-gr.nin contact in these sands. The beds of , (I)-The Athabasca oil is oil that escaped through bitumen reported during early exploration have not fissures from Devonian reservoirs and accumu­ been verified in subsequent coring. There is no neces­ lated in the MclVlurray sands during or since sity for the in situ theory of origin for the Athabasca Early Cretaceous time (Link, 1951; Sproule, deposit. There is no support for the theory if it is ad­ 1951) . mitted that the other accumulations along the heavy (2)-The Athabasca oil was derived in situ from oil belt are genetically related to the Athabasca de­ organic material deposited with the sand (Hume, posit. 1951; Corbett, 1955). The heavy oil accumulations are related to facies (3)-The Athabasca oil was derived from Clearwater and so a local source from fine-grained rocks (Hypo-' shales or nearby fine-grained rocks equivalent thesis 3) might be suspected. The volumetric requil'e­ , in age to the McMurray Formation. ments for such a source appear to be prohibitive. If " (4)-The Athabasca oil was ol'iginally light oil that the oil were derived from a prism of shaly sediments migrated out of the deep basin and has since 600 miles long, 140 miles wide and 1,000 feet thick, been altered to heavy crude (Gussow, 1956). these sediments would have to be 45 times as prolific (5)-The Athabasca oil was derived from materials as the average fill of the Los Angeles basin, the from soils leached iuto the Mcl\oIurray sauds and world's richest basin in terms of ultimate oil reserves converted to heavy hydrocarbons (Hodgson and per cubic mile of sediment. The associated shales are ..... Hitchon. 1965). not rich in organic material, and so an hJ.rpothesis of A sixth alternative, 1vhich accounts collectively for local source could he accepted only if evidence were the Athabasca deposit and the othel' heavy oil accum­ produced that there has been extremely efficient ulations along the belt, is advanced here as a working stripping of hydrocarbons from the associated fine­ hypothesis. This hypothesis accounts for the accumu­ grained rocks. lations by long-distance migration of organic material Derivation of large quantities of petroleum from in compaction waters containing natural solubilizers, soils (Hypothesis 5) seems quite unlikely, as has been with deposition of the heavy oil occurring where phys­ pointed out by Hedberg (1964, pp. 1762-1763). ical-chemical conditions were suitable. The micellar The most tenable working hypothesis to explain , ' mechanism overcomes many of the difficulties inher­ the emplacement of the huge quantities of viscous oil ent in the older hypotheses and is favoured. lies in the "micellar theory" of Baker (1959, 1960, Chemical studies of ',,"estern Canadian Lower Cre­ 1962). Briefly, the theory postulates that when or­ taceous crude oils have provided considerable evi­ ganic acid salts dissolve in water, clusters of individ­ ,.. dence. mainly of a negative nature, on origin. Trace ual molecules, known as micelles, are formed. The metal content. sulphur isotopes and the chemical char­ organic acid salts greatly increase the water solubil­ acter of high-molecular-weight compounds have ity of hydrocarbons because the clusters provide hy­ shown that the Athabasca oil is chemically, as well as drocarbon-like regions ,in the water in which the hy­ .~ , superficially, similar to other heavy oils from the drocarbons preferentially dissolve. Evidence support­ Lower Cretaceous belt, particularly those from Bon­ ing the theory is found mainly in the correspondence nyville and Lloydminstel' (Scott et al., 1954; Thode between the relative abundance of hydrocarbons with­ et aI., 1958; Schrayel' et al., 1960). A numhel' of lines in groups in crude oil and the relative solubility of of evidence show that the Athabasca oil is young and the same hydrocarbons in the micelles formed by col­ immature and is not evaporated, altered or polymer­ loidal electrolJ.rtes. A salt of an organic acid, sodium ized oil. The evidence includes the general chemical naphthenate, has been reported in oilfield waters in nature and instability of the oil (Ball, 1935; Mont­ excess of that required to form a micellar solution of gomery. 1951; McNab et al., 1952), the thermal in- the necessary concentration. According to the hypo-

Technology, October-December, .1965, Montreal 173' POOR IMAGE DUE TO ORIGINAL DOCUMENT QUALITY

WESTERN CANADA BASIN UPPER MANNVILLE MIGRATION ISOPACH-FISH SCALES BASE TO LOWER MANNVILLE

\ i '"" i ~ ~ _L_?- -

Figure 14. Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021 thesis, h.ydl'ocarbom; in the source sediments are dis­ minster structural feature where the oil was de­ soh'ed by compaction waters containing the natural posited. solubilizers, are transported in water solution and The hypothesis of migration of hydrocarhon~ in are abruptly released as they encounter environments ,vater solution is consistent with presently known with different ionic concentrations. Differences in the geological and chemical facts. The oil OCCLlrs in early­ composition of crude oils are explained by different formed stratigraphic and structural traps which could histories of the carrier solutions as migration oc­ have sen'ed as loci of deposition because of the dif­ cuned and different proportions of ionic (small) mi­ ferent conditions of water salinity, pressure or tem­ celles and neutral (large) micelles in the compaction perature that prevailed there. The accumulntions re­ waters. semble conventional oil pools insofar as the sand The different rOlltes that compaction waters \vould grains are w::tter-wet. The oil in the traps has under­ take through Lowel' and Upper Mannville rocks dur­ gone an adjustment determined by buoyancy llnd ca­ iug Early Cretaceous time are shown in Figures 13 pillarity, although this adjustment may be incompleLe and 1..\:_ The compaction waters would move from as yet because of the extremeb' high viscosity of some areas of high lithostatic load into areas of minimum of the oil.s. Apparent anomalies in the relationships potential where there is an easier escape route for of oil sand to water ,sand occur, particularly in the overpressured formation fluids. The compaction wa­ Athabasca and \Vabasca deposits, because in places ters would move to the basin margin or to a local the density of the oil is close tu or slightly greater margin, as at Peace River, or to early-formed domes, than the density of the formation watel". Migration anticlines or fault-line features, as along the Atha­ in water solution into some of the lenticular reser­ basca to Lloydminster trend. Release of the hydrocar­ voirs is difficult to envisage, but these lenticular oc­ bons from micellar solution would occur where less CUlTences can be explained more readily only if one saline waters were encountered (Baker, 1960) or pos­ appeals to a very local source for the oil. siblJ! where there was an abrupt change in other physical-chemical conditions such as pressure or tem­ CONCLUSIONS perature ('Meinschein. 1959). The oil would be de­ posited as large masse:i that would then follow the I.-The Lo,.."er Cretaceous heavy oil accumulations be­ entnr pressure law:i of buoyancy and capillarity. tween Peac.e River and Lloydminster are PUl't of The Fish Scales to Lower Mannville isopach of Pig­ a single oil 5J'stem or province. 'll1'es 13 and 1-4. represents the structure of the Lo\"... er 2.-The accumulations al-e situated in a marine-con­ Mannville at the end of Early Cretaceous time. Com­ tinental transition facies, but the coincidence of p3.ction w::tters from Cretaceous shale~ (and other accumulation with facies is not sharp. Mesozoic rocks?) in the Peace River basin moved through Lower l\'1annville sandy beds updip to the 8.-The heavy oil occurs in early-formed stratigraphic northeast and through gaps in the high ridge on the and structural traps. The belt between Athabnscil sub-Cretaceous unconformable surface (Figw'e, 18). and Lloydrninster lies along an early-formed anli­ The path of the flu!ds would be confined to the north­ clinal feature associated with salt solution. west by a facies change to shale. Oil deposition oc­ 4.-The most logical hypothesis for emplacement is curred at the local basin mm"gin at Peace River and by long-distance migration of hydrocarbons in on the west flank and top of an Early Cretaceous water solution. dome at 'Vabasca and Athabasca. The fluids could not cross the "\Vinterburn-Woodbend barrier and no sig­ ACKNOWLEDGMENTS nificant Lower l\olannville oil occurs east of this ridge south of Tp. 64. The paleostructural high in south­ This work was done while the writer was an em­ probably still had a high hydrostatic ployee of Imperial Oil Limited. Thanks are extended potential due to great distance to the basin margin. to Imperial's management for permission to publish The paths of compaction waters through Upper Mann­ and to G. A. Stewart, R. A. Rudkin, D. W. Spenoer ville rocks. confinEd by a northward facies change to and C. R. Evans for helpful comments and sugges­ shale, are shown on Figlire 1.4.. The compaction waters tions and for making available data essential to the could move heely eastward onto the Cold Lake-LIl)yd- study.

174 The Journal of Canadian Petroleum POOR IMAGE DUE TO ORIGINAL DOCUMENT QUALITY

REFERENCES CITED Mellon, G. B .• 1956) "Geology of the :McMurray Forma­ tion; Pt. II, Heavy .Minerals of the McMurray -Forma­ tlon;" Alberta Research Counc_, Rept. 72, pp. 30-4;:1- Baker, E. G' l 1959, "Origin and :Migration of Oil;" Science, v_ 129, pp_ 871-M74_ Jlellon, G. B_, and J. H. J.Vall, 1956, uGeology of the r..'Ic­ Baker, E. G., 1960, (fA Hypothesis Concerning the Ac­ Murray Formation; Pt. I, of the Upper cumulation of Sediment Iiydl'ocarbons to Form .Crude McMurray and Basal Clearwater Formationsj" Alberta Oil;" Geochim.. and Cosmochim. Acta, v. 19, pp. 309­ Reseal:'Ch Counc., Rept. 72, pp. 5-29. 317. Montgomery, D. So. 1951, "On the Origin of Athabasca Baker, E ..G., 1962. "Distribution of Hydrocarbons in Pe­ Oilj" Proc_ Athabasca ,Oil Sands Conference, Board of troleum;" A1JW1". Assoc_ PetTolewrn GeaL Bull., v. 46. Trustees of Oil Sands Project, Queen's Printer, Edmon­ pp. 76-84. ton, pp. 76-87. BaJ.l, ilt. W_ 1935, "Athabasca Oil Sandsj apparent ex­ Pow, J_ R., G. H. Fairbanks and W. J. Zamol-a, 1963, ample of iocal origin of oil;" Amel". Assoc. Petroleum "Descriptions and Reserve Estimates of the Oil Sands Gool. Bull., v. 19, pp. 153-171. of Alberta;" Alberta Research Counc_ Inform_ Ser_ 45, Came1"On, E_ Ai., 1965, "Application of Geochemistry to Clark Vol., pp. 1-14. Stratigraphic Problems in Lower Cretaceous of West­ Rudkin, R. A., 1965, "[Geological history of] Lower Cre­ taceous;JI in. Geological History of Western Canada. Al­ ern Canada;" AmeT_ Assoc. Petroleum, GeoL Bull., v. <: .' 49, pp. 62-80. berta_ Soc. Petroleum Geol., Calgary. chapt. 11, pp. 156­ Ca1Tigy, ~lf. A" and W. J. ZU71W1"a, 1960. "The Athabasca 168. Oil Sands;" in Oil Fields of Alberta, Alberta Soc. Pe­ Sclwayel", G. J., T_ J. 'flteismann and W. JlI. Zan'ella, troleum GeoL, Calgary, pp. 38-49. 1960, "Geochemical Studies on the 1ic:iV[urray Sand Oil Coleman, H. J., C. J_ Thrrmpson, H_ T. Rall and H. ill. and Selected Alberta Basin Crude Oils, (abstr.);JJ o. Smith, 1953. "Thermal Instability of High-Sulfur Crude Geol. Soc. America Bull_, v. 71, p. 1968. Scott, Jean, G. A. Collins and G. TJr. Hodgson, 1954, Oilsj" Indust. and Eng_ Chern., v_ 45, pp. 2706-2710. Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021 "Trace Metals in the McMurray Oil Sands and Other C01-bett. C. S., 1955, "In situ, Origin of McJ}Iurray Oil of 1"'- Northeastern Alberta and its Relevance to General Cretaceous Reservoirs of Alberta;" Trans., C.I.l\i., v_ Problem of 'Origin of Oil;Jr Anu~T. Assoc. Petroleum 57, pp. 34-40. Gool. Bull., v. 39, pp. 1601-1649. Sprou.le, J. C., 1951, "The McMurray Formation in its Glaister, R. P., 1959, "Lower Cretaceous of Southern Al­ Relation to Oil Occurrence;" Proc. berta and Adjoining Areas;" A11Wl·. Assoc_ Petroleu.m Conference, Board of Trustees of Oil Sands Project. Gool. Bull., v. 43, pp. 590-640. Queen's Printer, Edmonton, pp. 6-25. Stewa1·t, G_ A_, 1963, uGeological Controls on the Dis­ GussowJ W. C., 1956, "Athabasca Bituminous Sands;" in Symposium Sobre Yacimientos de Petroleo y Gas, Torno tribution of Athabasca Oil Sand Reserves;" Alberta III, XX Congreso Geologico Internacional, Mexico, pp. Research Counc_, Injonn. 8e1'. ~5. Clark Vol., pp. 15-26. -. 68-7D. Thode. H_ G_. Jan Monster and H. B. Dunford, 1958, ('Sul_ .;t, Hedberg, H. D., 1964{ "Geologic Aspects of Origin of Pe­ phur Isotope Abundances in Petroleum and Associated troleum;" Amel'. ASSOC. Pctl'oleum GeoL Bull., v. 48, :i\faterials;" AnWl·. Assoc_ Petroleum Geol. Bull., v. 42, pp. 1755-1803. pp. 2619-41. Hodgson, G. W_, 1954, '·Vanadium, Nickel and Iron Trace fVilliams, G. D., H_ Baadsgaard and G. Steen, 1962, upo_ l\letals in Crude Oils of Western Canada;" Amer. As­ tassium-Argon Mineral Dates from the Mannville soc. Petroleum Geol. Bull., v. 38', pp. 2537-54_ Group;" Alberta Soc. Pet1'olemn GeoL Jount., v. 10, pp. Hodgson, G. fV., and Brian Hitchon, 1965, UResearch 320-325. Trends in Petroleum Genesis;" paper for 8th Common­ wealth Min. and Metall. Congress. Australia and New Zealand, Feb., 1965; Contrib_ No. 270, Research Counc_ Alta., Edmonton, 33 p., 4 figs. Dr. Laurence W. VigTCSS, c native of Hume, G. S') 1951. "Possible Lower Cretaceous Origin of Melfort, Soskctcbewcn, received his BJtumen in Bituminous Sands of Alberta;" Proc. Atha­ early educotion ot the nearby community basca Oil Sands Conference. Board of Trustees of Oil of Pothlow. He attended the University Sands Project, Queen's Printer, Edmonton, pp. 66-75. of Saskatchewan and received a 8.E. Link, T_ A" 1951. "Source of Oil in Oil Sands of Atha­ (geological engineering) in 1951 and on basca River, Alberta. Canada;" Proc. Athabasca Oil M,Sc. in 1952, He joined the California Sands Conference, Board of Trustees of Oil Sands Standard Compony, but left in 1954 to '.'.f-" ". :~ Project. Queen's Printer, Edmonton, pp. 55-65. do further groduote work at Stanford • -" -~'. -- Martin, Rudolf, and F. G_ S. Jamin, 1963, '·Paleogeo­ University, receiving 0 Ph.D. in 1961_ ,.

morphology of the Buried Devonian Landscape in From 1958 to 1965 he was with Im­ ''-"'- ':, Northeastern Alberta;" Alberta Research Counc., In­ perial Oil Limited in Calgary, and wrote ,. jorm_ Ser_ 45, Clal'k Vol., pp_ 3J-42_ this poper while attached to their Heavy ~:~~:~ : ~:. -.' McNah, J. G.. P. V. Smith, J1'., and R_ L. Betts, 1952, Oil Group_ In June, 1965, he joined -~. '. .'-::" "The Evolution of Petroleum;" Indust. and Eng. Chem., Western Resources Consultants Ltd_ of .~ v. 44, pp. 2557-2563. Calgary_ Jl1einschein, W_ G., 1959, HOrigin of Petroleum;" Amer. Assoc_ Petl'olemn Geol. Bull., v. 43, pp_ 925-943.

L:~'-"'>~:: Discussion •• • ••• • • • • • • ~.~,~h\ ~: -.'- - - ~-- " , N discussing the Cretaceous The Cretaceous heavy oil reser­ beneath the unconformity is also ~__ :_j I. ,; • voirs, which 1\.11'_ Vigrass correctly heavy and viscous. Any explana­ I heavy oil deposits, 1\11". Vigrass '. has taken up the interesting prob­ recognizes as parts of a single oil tion of the Cretaceous heavy oil lem of their origin. However, the province, are only part of a great province - particularly one pro­ explanation may not be as impor­ regional pattern involving normal posing long-range migration...... :... tant to the industry as the recog­ crude oil and gas as 'well as heavy must also account for the gas to nition that oil and gas al'e distrib­ oiL Similar Cretaceous reservoirs the west and a similar gas to heavy uted in clearly defined regional under similar structural situations oil pattern in the underlying Dev­ patterns. The kind of hydrocarbons contain gas farther west and nor­ onian_ - gas, gas condensate, oil or heavy mal oil still farther west. Although Two major gas-oil distribution oil - likely to be present in any Devonian oil may be different from patterns are apparent in Western given reservoir in any given area the Cretaceous oil, nevertheless in Canada. ~ one involves the un-eroded can be predicted with great con­ the Cretaceous hea,'Y oil area, oil Mississippian and Devonian reser­ fidence. in the Devonian rocks immediatehr voirs; the other involves Cretace-

Technology, October-December, 1965, MClntreal 175 POOR IMAGE DUE TO ORIGINAL DOCUMENT QUALITY

DUS and Triassic reservoirs as well Explanations of these patterns differentiation. The possibility that as the eroded Mississippian and must not only account for migra­ methane may have a separate ori­ Devonian reservoirs immediately tion but also differentiation. Mi­ gin from oil, while at the same helm\'_ The lower system exhibits grating formation water - as a time critically affecting the mo­ a pattern of dry gas, with H:,lS consequence either of basin com­ bility of oil by its presence or ab­ and CO:! neal" the mountains pass­ paction 01" abnormal pl'essures de­ sence, further complicates the ing eastward into wet gas, then to veloped during mountain building problem. normal oil with decreasing GOR's, - is a ready vehicle for hydrocar­ and finally to the east to heavJ~ oiL bon migration. Differential solu­ No simple explanation fits nil The pattern of the upper system is bilit~r, differential entrapment, and the facts, but the regional distribu­ that of oil on the west near the alteration due to the physical and tion pattern is a firm basis for mountains, dry gas farther east chemical action of rock on transi­ planning exploration and develop­ and heavy oil on the extreme east. ent oil all rna3' be factors affecting ment. Gemld P. Salisb"TU Union Oil Co. of Canada Ltd., Calgary. Alberta Downloaded from http://onepetro.org/jcpt/article-pdf/4/04/168/2165766/petsoc-65-04-01.pdf by guest on 01 October 2021

Authors Reply. ~ 0 .0. • • ••

HE major problem of genesis has observed that ".... hether an oil is tion pattern. T peculiar to the Lower Cretace­ paraffinic, naphthenic or aromatic The gas-oil pattern in the Devon­ ous heavy oil s3rstem lies in the probably depends less on the nature ian and Mississippian strata ap­ concentration of a vast quantity of the original source sediment pears to be independent and sep­ of hydrocarbon material in a rela­ than it does on the proportions of arnte from the pattern in the Low­ tively small volume of rock. It ionic and neutral micelles in the er Cretaceous rocks. The heuv)' must be admitted, nevertheless, transporting water, probabty de­ viscous oil found in eroded Devon­ that a comprehensive explanation pendant in part on the sieving ac­ ian beds in northern Alberta is of the heavy oil accumulations must tion of the compacting sediments. probabl;v Lower Cretaceolls oil that also account for the regional pat­ During migration, the paraffinic has been deposited in pore space tern of distribution which has compounds may be less soluble and available in the Paleozoic roelt be­ Cretaceous light oil in the west could be released from the water low the unconformity_ with dry gas to the east overlap­ solution to form oil earlier than ping onto a heavy oil province are the naphthenic. compounds. along the basin margin. The com­ Presumably, proc.esses of matura­ Reference Cited plex factors which are considered tion, both while the hydrocarbons important in establishing the gas­ are in transport and after the oil Bakel', E. G., 191i2, "Distribution of Hydrocarbons in Petroleulll;" oil pattern have been mentioned by has been pooled, ' ...·ould be impor­ Amer. Assoc. Pl'fl'o{elllll CeDI. Bulf., :Mr, Salisbury. Baker (1962, p. 83) tant in establishing the distribu- ". 46, pp. 76-84. L. HI. l'igms,.

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Discttssi01l is invited ou papers appearirLg m the ]oumal. Discussion on auy paper JI'ill not be considered after six months from date of publication.

176 The Journal of CClnodion Petroleum