Chemical Geology, 93(1991)61- 7861 El sevi erSci encePubl i sher sB.V.,Ams t e r da m Bi omarkerdi stri buti onsincrudeoilsandsourcerocksfrom differentsedi mentaryenvi ronments* FanPu a, R.P.Philp b, Li Zhenxi a, YuXinke a andYing Guangguo~ ~Lanzhou Institute of Geology, Academia Sinica, Lanzhou, People's Republic" qf China bSehool of Geology and Geophysics, University of Oklahoma. Norman, OK 73019, US.4 (Recei ved March5,1990;revised andacceptedJanuary21,1991) ABSTRACT FanPu,Philp,R.P.,LiZhenxi, YuXinkeandYingGuangguo,1991.Bi omarkerdistributionsincrudeoilsandsource rocksfromdifferentsedimentaryenvi ronment s. In:J.A.Curiale,R.AlexanderandP.W.Brooks(Edi t ors), Organic Geochemi st ry ofHydrocarbonBasins.Chem. Geol.,93: 61- 78.Thesaturatedandaromat i chydrocarbonsfromasignificantnumberofoilsandsourcerocksderi vedfromterrestrial andmarineorganicmat t erhave beenanalysedby GC andGC-MS. Results show thatcertainclasses ofbi omarkersinclud- ing bicyclic sesquiterpanes,tricyclic terpanes,pregnanes,methylsteranes,rearrangedsteranes,hopanesulfides,benzoho- panes,long-chainalkylbenzenesandpentacyclictriterpanescanbeusedtodistinguishdifferencesinsourceinputa nd/ ordepositionalenvi ronment s. Variationsinthedi st ri but i onsofthenaphthalenes,phenanthrenes, fluorenes,dibenzofurans,di benzot hi ophenes, napht hobenzot hi ophenesandt ri aromat i csteroidhydrocarbonsmayalsoreflectdisparitiesinsource inputor sedi ment aryenvi ronment s.1.Int roduct i on In recentyears,increasing at t ent i on has been gi ventot hedi st r i but i onsof bi omar ker sin cr udeoilsandsourcerocksandt hei rabilityto pr ovi dei nf or mat i onondi fferencesindeposi - t i onal envi r onment s andt ypeoforgani cmat - teri nput . Sixty-seven sampl es ofcrude oils and sourcerocksf r omdi fferent basi nsandsedi- ment ar yenvi r onment shavebeeni nvest i gat ed in t hi sst udy. Thesat ur at edandar omat i cfrac- t i ons f r om t hesesampl es were anal ysed by GC- MSt oi nvest i gat et hei r geochemi calcharact eri st i cs.Thesampl esanal ysedint hi sst udyi ncl ude:10oilsand18sourcerocksf r omafreshwat er *Thisr esear chisacooper at i vepr oj ect f undedbyAcade-mi aSi ni ca andNSF, USA aswell asapar t i al resul t oft he pr oj ect 4870137s uppor t edbyt heNat i onal Nat ur al Sci- enceFounda t i onofChi na.envi r onment int heShaanxi - Gansu- Ni ngxi a Basin,Chi na; 12oilsf r omasalinel acust ri ne e nvi r onme nt int heCha i da muBasin;6oils f r omt hel acust ri neJi anghanBasinwhi chis mor esalinet hant heCha i da muBasin;and3 oils and16 source rocks f r om amar i ne carbon- atesedi ment ar ye nvi r onme nt int heSout h Fl or i da Basin,U.S.A.(Tabl es1-5andFig.1 ). All t hesourcerocksampl esf r omt heShaanxi - Gansu- Ni ngxi aBasinhavebeenshownina numbe r ofpr evi ousdet ai l edi nvest i gat i onsto beresponsi bl efort heoilsampl esint hi sbasi n ( FanPuetal.,1980,1984). Inor der tosim- plifyt hei nt er pr et at i onofbi omar ker saffect ed byvar i at i onsinsourceanddeposi t i onal envi- r onment s,t heselected sampl es werechosen to beof si mi l armat ur i t ylevelsandvi t ri ni t ere- fl ect anceval ues(Ro)of allt herocksampl es werelesst han0.6%( FanPuetal.,1984;Pa- lacasetal.,1984). Bi omar ker par amet er styp- 0009- 2541/ 91/ $03. 501991El sevi erSci encePubl i sher sB.V.Allrightsr eser ved.62 TABLE1 Sourcerocksf r omShaanganni ng Basi n( f r eshwat er bas i n)F~NPtlET AL WellnameAgeDept hDeposi t i onTypeofrock ( m)Ling148T~1666.00Deeplake Ling 96T31755. 76-1759. 91Deeplake Fu2T 3829. 48- 833. 48Deeplakc .lic2-674T3617. 24Deeplake Qi ng11T32091. 00- 2092. 00Deeplake Sai71T 31024.00Deeplake LiIT 32091. 00- 2093. 00Deeplake Ling52T31917. 66- 1920. 46Deeplake H ua49T31930. 00- 1940. 00Deeplake Ji c2-674T 3756.00Deeplake Guo2T32225. 95- 2227. 65Deeplake .lie2-674T~928. 80Lake-swamp Hongj i ngzi 5-11J~1827. 40- 1837. 30Lake-swamp Ling128J~1290. 50- 1293. 00Lake- swamp Hongj i ngzi 11-9Jt1995. 90- 1999. 94Lake- swamp Ling214J,1297. 16- 1304. 75Lake-swamp Ling11J,1291. 86- 1298. 70Lake-swamp Wu33Jl 1130. 00- 1133. 50Lake- swamp Grey-bl ack muds t onewi t halot ofpl ant fract i ons Dark-greymuds t one Black car bonaceousmuds t one Black-grey muds t one Black shal e Gr ey- bl ackmuds t one Blackmuds t one Black muds t one Black car bonaceousshale Black car bonaceousmuds t onewi t hpl ent y ofpl ant fract i ons Dark-greymuds t onewi t hpl ant andcar bonfract i ons Grey-greenmuds t one Dark-greymuds t one Grey-bl ack muds t one Black shal e Black shale Black muds t one Dark-greenmuds t onewi t hpl ent y ofpl ant f r act i ons TABLE2 Sourcerocks andcrudeoils f r omt heSout hFl or i daBasi n WellAgeDept hEnvi r onme ntofTypeofrock No.(ft . )deposi t i on R-5KL R-7K, R- I I KI R-8Ki R-14KI R-6K, R-13K, R-18KI R-19Kt R-10K R-4K R-12K R-9K R-15K R-16K R-17K 0- 5K 0- 6KI O-7KI 11521- 11525 11566- 11569 11580- 11584 11690-11691 11630-11631 11873- 11874 11873- 11874 11847- 11848 11725- 11726 11731- 11732 11735- 11736 11664- 11665 11668- 11669 11393- 11394 11464- 11465 11484- 11485 Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Mar i ne Grey-bl ack l i mest one Black oi l -beari ng l i mest one Grey-bl ack argi l l ousl i mest one Light-grey l i mest one Dark-greyl i mest one Black l i mest one Black l i mest one Black-greyl i mest one Grey-bl ack l i mest one Black argillous l i mest one Black argi l l ous l i mest one Gr ey- bl ack argillous l i mest one Grey-bl ack l i mest one Gr eybi ocl ast i c l i mest one Li mesandst one Grey-bl ack car bonaceousmuds t one Sunni l and oil Sunni l and oil Sunni l and oil BIOM RKER DISTRIBUTIONS IN CRUDE OILS AND SOURCE ROCKS6 3 TABLE3 Crude oils from Shaanganning Basin(freshwater basin) WellnameAgeDepthEnvironment of (m)deposition Hua50T 31406.9-1408.0Deep lake Qing15T31625.6-1692.2Deep lake Qing 21T~1777.0-1790.6Deep lake WanglJ~1774.2-1779.0Lake-swamp Ling 55J~1268.6-1273.4Lake-swamp Ling145J~1565.4-1572.8Lake-swamp Wang14J~1924.4-1926.0Lake-swamp Ling166Jt1701.4-1711.0Lake-swamp Lingnan176Jh1335.6-t337.0Lake-swamp Lingnan 44J~1338.0-1368.0Deep lake TABLE 4 Crude oils from JianghanBasin(saline basin) WellnameAgeDepthEnvironment of ( m )deposition Guang3-10E2375.8-2567.0Salt lake Wang 3-2E1422.0-1539.4Salt lake Zhang 3-4E1604.8-1618.0Salt lake Guang16E2953.6-2959.8Salt lake Guang54E3448.6-3462.0Salt lake Wangxi12-11E2931.0-2937.0Salt lake TABLE 5 Crude oils from Chaidamu Basin Well nameAgeDepthEnvironment of ( m )deposition Zong11N2266.96-831.53Salt-waterlake Yue 42N 22122.00-2125.00Salt-waterlake Zhong 6N263.61-212.20Salt-waterlake Zhong 8N2106.03-611.01Salt-waterlake Can1N~2254.00-2447.20Salt-waterlake Shen2N~657.28-816.29Salt-waterlake ZhongtN~1039.00-1259.80Salt-waterlake Zhong 20NL658.00-858.55Salt-waterlake Shen1E32331.50-2381.57Brackish-waterlake Can2E 32562.00-2569.20Brackish-waterlake Shen 7E33300.50-3322.72Brackish-waterlake Di1E 31366.40-1368.00Brackish-waterlake Yuzhong1J2Fresh-water lake-swamp icallyusedtoevaluatematurityofoilssug- gested that the oils examined in the study were of similar maturity levels. Since thisstudy was mainly concerned with variations in source and depositionalenvironments,noattempthas been made tofurther evaluate effects of matu- ritysincethishasbeenadequatelydescribed by other workers (Seifert and Moldowan,1978; Radkeetal.,1982a,b,1986;Alexander etal., 1984,1985;Garriguesetal.,1984,1988: Hughes,1984;Mackenzie,1984;Palacas et al., 1984). 2.Experi ment alThe source rock samples were extracted with chloroformusingSoxhletextractors.Theex- tracts and crude oils were separated by column chromatography, andtheseparatedhydrocar- bonfractionsanalysedonaHP5890Acapri- lary gas chromatograph coupled to a HP5988A quadrupole mass spectrometer system. The GC wasequippedwitha50m0. 32mmi.d.SE- 54fusedsilicacapillary columnandtheoven temperaturewasprogrammedfrom80Cto 200Cat 6C/ mi nand then to 300Cat3C/minwithHeascarrier gas.Typicaloperating conditionsforthemassspectrometer operat- ing under electron impact conditions were: ion source temperature 200 C and electron energy 70eV.The detector andinjector temperatures weremaintainedat300C.Bothselectedion monitoring(SIM)andfull-scan(FS)tech- niques were used in the GC-MS analysis. Iden- tificationofvariouscomponentsinthemass chromatograms was based on the combination ofmassspectra,retentiontimesandprevi- ously published literature data. 2.Resul t sanddi s cus s i on 2. 1. Saturatedhydrocarbons Thesaturatedhydrocarbonfractionsiso- lated from the crude oils and source rocks were found tocontainseveral series of biomarkers, whoseabundancesandconfigurationswere found tobeuseful indifferentiating sedimen- tary paleoenvironments. 64F ANP U E T AL,Z HUNGE E R i q ' . . . . . . . .S e d i m e n t a r y b a s i nS a m p l i n g b a s i nSONGLIAOBASI N ~ '-;BEI J I . - " ' "BOHAIGULF BASI N : { S HAANGANNI NGBASI NYELLOWSEA S o u t hC h i n a S e as o u . . .,NAf / ' i-/J Fig.1. DepositionalbasinsofChinaand locations offieldssampled. 2.1. I.Normal alkanes n-Alkanedistributionsofthesourcerocks and crude oils from the saline lacustrine basins such as the Chaidamu and Jianghan Basins and theSunniland Oilfield generally show aneven carbonpredominanceintheC23-C35 carbon numberrangeandtheirpri st ane/ phyt anera- tiosweretypically lessthan1.Suchdistribu- tionsof n -alkanesandisoprenoids have been previously described byPalacasetal.(1984) fortheSunnilandsamplesandreflect there- ducingnatureoftheoriginaldepositional environment. 2.1.2.Bicyclicsesquiterpanes Bicyclic sesquiterpanes were present in all of thecrudeoilsandsourcerockextractsexam- inedinthisstudy.Approximately 23isomers of bicyclic sesquiterpanes in the C~2-C21 range were found toexist insamplesfrom thesaline lacustrineenvironments,namelytheChai- damu Basin and the Jianghan Basin.Therela- tive abundance of the Cl3,Cl4 andC~5 sesqui- terpanesincrudeoilsfromthehypersaline environmentwashigherthanthatfromthe freshwaterenvironmentandmajorcompo- nentsinthem/ z 123masschromatograms of BIOMARKER DISTRIBUTIONS IN CRUDE OILS AND SOURCE ROCKS65 t hecr udeoilsandsourcerocksi ncl udedri- mane(C15H28),andhomodr i ma ne (C16H3o (Fig.2). Inmost cr udeoilsf r omt hefreshwa- t er e nvi r onme ntdr i mane( peak13)is t hema- j or component ,whileinsourcerocksf r omt he sameenvi r onment , aswellascrudeoilsf r om t hehypersal i nesedi ment ar yenvi r onment ,t he maj orc ompone ntis homodr i ma ne ( peak18 ). Int heSunni l andcr udeoils,t herelativecon- cent r at i on of bi cycl i c sesqui t er panes was l ower whenc ompa r e dwi t ht henonma r i ne oils,buthomodr i ma neisstill t hemaj orcomponent .Theabundanceof t het hreemaj or com-poundsin t he m/z123 chr omat ogr amsmay re- flectdi fferencesinorgani cmat t er i nput f r om vari oussedi ment ar yenvi r onment s . Therela- tiveabundances of t het hr eemaj or sesquiter- panes, 8, 10- di met hyl - 9- et hyl - per hydr onaph-t hal ene( peak7), dr i mane( peak13)and homodr i ma ne ( peak18)f r omsomeof t he sourcerocksandcr ude oilsst udi ed arepl ot t ed onat ernarydi agr aminFig.3.Cr udeoilsand sourcerocksf r omt hefreshwat er e nvi r onme ntpl ot inal ongandnar r owarea( I ) i ndi cat i ng t hepr edomi nanceof dr i maneandhomodr i -manebut ast hesalinityof t hee nvi r onme nti ncreasesso t heoilsampl es show arelativein- creaseof 8, 10-di met hyl -9-et hyl -perhy- dr onapht hal ene and pl otin aseparat earea(II; Fig.3 ). 2.1.3.Tricyclic terpanes Thetricyclict er panedi st r i but i onsint he crudeoilsandsourcerockextracts, t ypi cal l y falli nt ot womai nt ypes, ei t hert heresi n-t ype di t er penoi dsort heext endedtricyclicter- panes. Thedi t er penoi ds associ at ed wi t hresi ns of manyt ypesof hi gherpl ant s, part i cul arl y conifers, havebeendescri bedinmanypapers,part i cul arl y t hose concer ned wi t h oils f r om t he Mackenzi eDel t a( SnowdonandPowell,1982), oilsf r omt heGi pps l andBasin,Aus- t ral i a( Phi l petal.,1981;Nobl eetal.,1986),andoilsf r omt heTar anaki Basin,NewZea- l and(West onetal.,1989), whi chareallre- por t ed tobe ri ch in di t erpanes. Thefour maj ordi t er panesint hesampl esexami nedint hi s st udyare18- nor pi mar ane(C19H34),pi mar -ane(C2oH36), nor abi et ane(Cl9H34)and abie- t ane(C20H36).Thedi t erpanes, al ong wi t hrel- at i vel ylowconcent r at i onsof vari ous t et racycl i cdi t er panoi ds, reflectt hei nput oft erri genous source mat eri al s in t he source rocks andcrudeoilsder i vedf r omfreshwat erenvi- r onment s (Fig.4A). Thedi t er paneswerenotobserved to be presentin t he oils or source rock extractsf r omt hesalineandhypersal i neenvi- r onment s. Theoilsf r omt heseenvi r onment sweredomi na t e dbytricyclict er paneswi t hex- t endedsi de-chai nsandrangi ngincar bon numbe r f r omC18 toC3o, andpr obabl yhigher,wi t hC23ast hedomi na nt c ompone nt (Fig. 4B).2.1.4. Pregnanes Theconcent r at i ons ofpr egnanes andhomo-pregnanes, asdet er mi nedf r omt hem/z217 chr omat ogr ams,insource rocks andcr ude oils f r om t he saline and mar i ne envi r onment swere obser vedtoberelativelyhi ghert hant hoseoft hesampl esf r omt hefreshwat erenvi r onment .Most of t hesampl escont ai nedfourC21H36 pr egnane i somers,t wowi t h t he5o~ ( H) - conf i g-ur at i on(2and3)andt wowi t ht he5f l ( H) -confi gurat i on, peaks1and4.Thering-A- methyl-5o~ ( H) pregnane i somer corresponds to peak( 6) andringAmet hyl - 5f l ( H) - pr egnane cor r espondstopeak( 7) , andpeak( 8) corre- sponds to5 o~ ( H) - homopr egnane( Fig.5 ). 2.1.5. Methylsteranes Aseriesoft heCz8-C30met hyl st er aneswas f oundincr udeoilsf r omt hesalineandhyper- salinesedi ment ar yenvi r onment s inrelatively lowabundanceandwi t hapr edomi nanceof5o~(H)-met hyl st eranes. Incrudeoilsand sourcerocksf r omfreshwat erenvi r onment s ,met hyl st er aneswereabsent orpresent inex- t r emel ylowconcent r at i ons. Noat t empt was madetodet er mi net heposi t i onoft hemet hylgr oupduetot helowconcent r at i onsof t hese component s .66F ANP U E T AL.i ) ( 0 i!,