organic geochemistry 06

1. Fundamentals of Organic Geochemistry2. Origin and Formation of Petroleum3. Maturity4. Migration and Trap5. Source Rock Evaluation6. Oil-Source Rock Correlation and Biodegradation7. Modeling

Organic Geochemistry of Petroleum SystemDr. SAMPEI, Yoshikazu

Professor, Department of Geoscience, Faculty of Science and Engineering, Shimane University, E-mail:[email protected]

“ Petroleum Formation and Occurrence ”

“ The Biomarker Guide ”

“ Introduction to Organic Geochemistry ”

Organic Geochemistry of Petroleum System

Dr. SAMPEI, Yoshikazu Professor, Department of Geoscience, Faculty of Science and

Engineering, Shimane University, E-mail:[email protected]

Contents

1. Fundamentals of Organic Geochemistry ------------------------(4)(1)Components of oil

(2)Biomarker (3)Labeling system

(4)Symbols of chemical structure (5)Modifiers on chemical structure (6)Stereo-isomer (7)Optical isomer (8)Racemization (9)Important analytical equipment : GC (10)Important analytical equipment : GC/MS (11)Representative GC/MS result: Selected ion chromatogram

(12)Representative GC/MS result: Full scan and mass chromatogram 2. Origin and Formation of Petroleum --------------------------(16)

(1)Kerogen Type (2)Depositional environment of kerogen type (3)Caracterization of Kerogen: bulk composition (4)Kerogen formation: classical and diagenetic path (5)Kerogen formation: new concept (6)HI and OI (7)Van Krevelen diagram and HI-OI (8)Rock Eval (9)Interpretation of Rock Eval (10)HI and H/C (11)Petroleum system (12)Crude oils characterization (13)Crude oils characterization 2 (14)Hydrocarbon compositions (15)Terpanes (16)Terpanes

(17)Aromatics (18)Organic sulfur compounds

(19)Organic nitrogen and oxygen compounds (20)Biogenic methane

3. Maturity ------------------------------------------------------------(36)

(1)Diagenetic compositional changes in hydrocarbon (2)Diagenetic change in chemical structure of kerogen (3)Vitrinite Reflectance (4)Maturity indicator of biomarker (5)GC/MS SIM chromatogram of oil (6)Relationship between two biomarker maturity indicators 1 (7)Relationship between two biomarker maturity indicators 2, (8)Non-biomarker maturity indicators in postmature zone

(9)Respond range of maturity parameter (10)Origin of methane

4. Migration and Trap ----------------------------------------------(46)

(1)Primary migration and secondary migration (2)Porosity and fluid pressurek (3)Porosity and permeability of reservoir rock (4)Microfracturing system in primary migration (5)Diffusion-controlled processes in primary migration (6)Molecular solution in water (7)Molecular solution in gas (8)Complex system for oil accumulation (9)Preferential expulsion

5. Source Rock Evaluation -----------------------------------------(55)

(1)Standard evaluation sheet for source rock potential (2)Source rock generative potential (3)TOC and S2 of shale (4)Controlling factors of TOC (5)S2-TOC plot (6)Lacustrine source rock evaluation (7)Biomarker as organic source indicator (8)Biomarker as organic source indicator (9)Age control of the C28/C29 steranes ratio (10)Oxic-anoxic proxy (11)Depositional environment indicator (12)Origin indicator (13)Depositional indicator (14)Origin indicator 2 (15)Origin indicator 3 (16)Porphyrin (17)Souce rock potential and environmental change

6. Oil-Source Rock Correlation and biodegradation ---------(72)

(1)Tool for oil-source rock correlation (2)Correlation by n-alkane

(3)Correlation by steranes and hopanes (4)Correlation by steranes (5)Confidence of oil-source rock correlation

(6)Biodegradation of n-alkane (7)Biodegradation stage (8)Biodegradation effect on sulfur&nitrogen contents and API

7. Modeling ----------------------------------------------------------(80)

(1)Changes in %Ro under different heating rate (2)Computer simulations based on kinetics of isomerization (3)Data set of kinetic parmeters (4)Simulation results

8. Reference ---------------------------------------------------------(84)

Contents

1-(1) Components of oilAsphaltens: Higher molecular weight (500-1500) NOS/polar compound; soluble in CS2; insoluble in n-C6H8 or n-C5H10

Resins: Higher molecular weight (less than 500) NOS/polar compound; soluble in n-C6H8 or n-C5H10

Molecular sieve: Separation based on molecular size by e.g. zeolite; small molecules become trapped in the crystal lattice.

Urea adduction: Small molecules become adducted by urea crystal (NH2CONH2); use to concentrate e.g. steranes.

Tissot and Welte (1984)

1. Fundamentals of Organic Geochemistry

1-(2) BiomarkerUseful tool to know:

Origin of organic matter; Depositional environment; Maturity; Correlation between oils and source rock.

Steranes

Peters and Moldowan (1993)

Hopanes

1-(3)Labeling system

Three-dimensional structure

To know: Maturity (Origin)


1-(4)Symbols of chemical structure

To depict the stereochemistry of atoms

Single bond: on the sheet plane

Light gray bond and white circle:directe into page

→ the alpha (α) position(The opposite side is beta (β) )

= Stereochemistry


1-(5)Modifiers on chemical structure

Homo-: one additional carbon on sturucture.

bis=ditris=tritetrakis=tetrapentakis=pentahexakis=hexa


Nor-: one less carbon on structure. Des-A: loss of A from structure. Iso-: methyl shifted on structure. Neo-: methyl shifted from C18 to C17 on hopane.

R: asymmetric carbon that obeys convention in a clockwise direction.S: asymmetric carbon that obeys convention in a anti-clockwise direction

1-(6)Stereo-isomer.

Important concept to understand maturity indicators of biomarker

Changes to the mirror-image structure by heated condition (These two are so called “enantiomers”)

These substituents form chiralmolecule.

Chiral molecule: The name is given to asubstituent with an asymmetric carbon at which optical isomers may occur.


1-(7) Optical isomer

The stereo-isomer shown in the previous page is an optical isomer, which can perform a rotatorypolarization.

Clockwise direction “dextro-rotatory”“R (rectus or dextral)” or,“D” or,“+”

Anti-clockwise direction “levo-rotatory”“S (sinister)” or,“L” or,“－“


1-(8) Racemization: Interconversion ofenatiomers is calledracemization.

Epimer EnantiomerEnentiomorphAntimer


The biological epimer20R-C29-5α, 14α, 17α(H)-sterane

changes to the geological epimer20S-C29 5α, 14α, 17α(H)-sterane

The ratio of 20S/(20S+20R) rises from 0 to about 0.5 (equilibrium at 0.52-0.55; seifert and Moldowan, 1986).


1-(9)Important analytical equipment : GC

GC: The separation of mixtures of compounds by partition between a mobile gas phase and stationary liquid phase is called gas chromatography (Miles,1994).

Capillary column is used to separate components of oils and rock extracts. .

1-(10) GC/MSThe tandem system of GC linked to a mass spectrometer; the most powerful analytical technique in modern organic geochemistry.

Organic compounds → separated →transfered to the ionizing chamber →accelerated → detected in the electron multiplier

Positive ions of mass/charge ratio (m/z) are impinge on the detector.

Analitical time: 1 or 2 hoursGC temp.: about 40 to 300 ºC.


Shimane Univ.

Shimane Univ.

1-(11)Representative GC/MS result:

Selected ion monitoring (SIM) is often used.

With 70eV electron impact (EI) ionization

SIM is very sensitive.


Steranes and hopanes have specific fragment ions m/z=217 and m/z=191, respectively.

These two ions are commonly used as routine biomarker analyses.

1-(12)Full scan + mass chromatogram

“Full scan ” condition is not so sensitive.

But “Full scan ” gives a detail information to know organic structure of unknown compound.

The detail information is “mass chromatogram”.

Major fragment ion & Mokecular ion


m/z=217

12

3

5

6

78

9

10

1211

13

1415

16

17 18

4Diacholestane 20R

Unpublished data (Akita-oil)

m/z=217C27 sterane 20R(cholestane)

C28 sterane 20R(ergostane)

C29 sterane 20R(stigmastane)

Representative GC/MS chart for steranes

Peak No. Name carbon number

1 A 13β,17α (H)-diacholestane 20R 272 B 13β,17α (H)-diacholestane 20S 273 C 5α,14α,17α(H)-24-norcholestane 20R 264 D 5α,14α,17α(H)-24-norcholestane 20S 265 E 5α,14α,17α(H)-cholestane 20R 276 F 5α,14α,17α(H)-cholestane 20S 277 G 5α,14β,17β (H)-cholestane 20R 278 H 5α,14β,17β (H)-cholestane 20S 279 I 5α,14α,17α (H)-24-methylcholestane 20R 2810 J 5α,14α,17α (H)-24-methylcholestane 20S 2811 K 5α,14β,17β (H)-24-methylcholestane 20R 2812 L 5α,14β,17β (H)-24-methylcholestane 20S 2813 M 5α,14α,17α (H)-24-ethylcholestane 20R 2914 N 5α,14α,17α (H)-24-ethylcholestane 20S 2915 O 5α,14β,17β (H)-24-ethylcholestane 20R 2916 P 5α,14β,17β (H)-24-ethylcholestane 20S 2917 Q 5α,14α,17α (H)-24-n-propylcholestane 20R 3018 R 5α,14α,17α (H)-24-n-propylcholestane 20R 30

m/z=191


C33 (S,R)

C32(S,R)C34 (S,R)

C31Homohopane (S,R)

C35 (S,R)Ts

Tm

C30Hopane

36:Oleanane 31:Gammacerane

Representative GC/MS chart for hopanes

Cholesterol

OH

OHStigmasterol

24α-ethylcholesta-5,22E-dien-3β-ol

Precursors of steranes

2-(1) Kerogen TypeKerogen: Insoluble; preserved in sedimentary rocks

Shimazaki (1986)

Type IV (inertinite) ：Woody&coalyoxidized and hydrogen-very-poorType II-S : amorphousunusually high organic sulfur about 8-14% (atomic S/C>0.04) and appear to begin to generate oil at lower thermal exposure

2. Origin and Formation of Petroleum

Type III (gas prone):Woody&coalyhydrogen-poor & poly-aromatic; higher plants

Type I (very oil prone): amorphoushydrogen-rich; algal in anaerobic; especially lacustrine.

Type II (oil prone): herbaceouscomparatively hydrogen-rich; phytoplankton in suboxic; especially marine.

As macerals (morphology)

Type-I

II

III

Killops and Killops (2005)

Structural characteristics of Kerogen

2-(2)Depositional environment of kerogen typeType I:

stratified freshwater lakesType II:

silled, deep-water basins on continental slope and riseouter shelf O2-minimum layer under upwelling

Type III:lagoonal, deltaic and coastal swampsbasins of restricted circulation on continental shelves

Type IType III Type III

Type IIType II

Type IType III Type III

Type IIType II


500-2500m without supply of clay


2-(3) Bulk composition: Van Krevelen diagram

Immature type I : high H/C about 1.7 and low O/C about 0.05.

Immature type II : medium H/C about 1.3 and medium O/C about 0.1

Immature type III : low H/C about 0.9 and high O/C about 0.2.


2-(4) Kerogen formation:classical and diagenetic pathLiving organisms are composed of:

LigninsCarbo-hydratesProteinsLipids

Macro-molecules to SugarsAmino acidsFatty acids

Polymerized to Humic acidKerogen

conifer wood broadleaf wood


lignin

Structural characteristics of Lignin


2-(5) Kerogen formation: new concept

Bio-macromolecules as lignins, carbohydrates, proteins and lipids are to humic substances.

Anoxic marine without Fe → hydrogen sulfides → organic sulfur → sulfur rich oil

Peters et al. (2005)

2-(6) Rock Eval HI and OIRock Eval hydrogen index (HI: mgHC/gTOC) and oxygen index (OI: mhCO2/gTOC) is simulating the Van Krevelen diagram.

Immature type I:high HI 900 and low OI 20

Immature type II:medium HI 500 and medium O/C 50

Immature type III:low HI 100 and high OI 100.

HI = S2/TOC

Example:S2=4(mgHC/gRock)TOC=2(%)HI = 4/(2/100) = 200 (mgHC/gC)


2-(7)Correlation between Van Krevelendiagram and modified Van Krevelendiagram.

Type I II III H/C 1.6, 1.3, 0.9HI 800, 500, 100

O/C 0.05 0.1 0.2OI 20 50 200


2-(8) Rock Eval

Anhydrous pyrolysisInstitute Francais du Petrole (IFP)

About 100mg of pulverized source rock sample

Hydrocarbon detected by FID (flame ionizetiondetector)

CO2 detected by TCD (thermal conductivity detector)

Shimane Univ.

Shimane Univ.


2-(9) Interpretation of Rock Eval

First at 300ºC: the peak area S1

Second at 300-550ºC(25 ºC /min): the peak area S2

Carbon dioxide up to a temp. of 390ºC: the peak area S3

HI: S2/TOCOI: S3/TOCTmax: ºC

<435 ºC (immature)435 to 460 ºC (mature)>460 ºC (post mature)

Whelan and Thompson-rizer(1993)

2-(10) HI and H/CQuantitative relationship

H/C = 0.0017HI + 0.5

O/C = 0.0036OI + 0.05.

C6H6 ： H/C=1

C10H8 ： H/C=0.8

C12H18 ： H/C=1.3

C14H10 ： H/C=0.71

C20H42 ： H/C=2.1


2-(11) Petroleum system

Anoxic condition: kerogen survives oxidation

Heated with increasing depth to release CO2 and H2O

Humic macro-molecule ( in diagenesis )Hydrocarbon ( in catagenesis )Gas ( in metagenesis )

Tissot and Welte(1984)

BiodegradationOxydationWater-washing

2-(12)Ternary diagramof oils

ParaffinsNaphthenesAromatics(&NOS)

Non-degradaded: Paraffins&aromaticsDegradaded: heavy oils; aromatics &NOS and much sulfur >1 %


BiodegradationOxydationWater-washing

Biodegradationonly

Thermal maturation

2-(13) “Alteration”:

Biodegradation+ water washing:Paraffins&Naphthenes decrease.

Maturation:aromatics+ asphaltenesdecrease.

Aromatics:absent in recent sediments;produced in the early diagenesis; decomposed in the catagenetic


2-(14)Hydrocarbon compositions

Soxhlet extraction (Shimane Univ.)

organic sulfur compoundsorganic nitrogen compoundsorganic oxygen compounds.

Based on boiling temperature, molecular weight and absorption affinity

alkanes (n-alkane)iso-alkaneCycloalkanesmono-aromaticsdi-aromaticspoly-aromatics


head

Isoprene unit:building block for terpenoids

diatom

2-(15)aTerpanes

Sesterterpanes (C25): AcyclicTricyclictetracyclic


2-(15)bTerpanes

Triterpanes (C30):AcyclicTricyclic

2-(16)a Steranes




2-(16)b Hopanes


2-(17)Aromatics


2-(18)aOrganic sulfur compounds


low matured high sulfur oil

2-(18)bOrganic sulfur compounds


pH control

Neutral nitrogenBasic nitrogen

2-(18)aOrganic nitrogen compounds



DPEP –––(maturation)–––> Etio

1

2

2-(18)bOrganic oxygen compounds

Mainly due to biodegradation

Suzuki, 2000 (鈴木 (2000) 監修，「生物図録」数研出版)

Chlorophyl-a

1

2


Early stage of diagenesis by methanogenicbacteria (methanogens) after working sulfate-reducing bacteria

Deltaic and coastal swamps: Activity of methanogenic bacteria is high because of abundance in organic acid (mainly acetate, indicating oxiccondition) and absence of sulfate-reducing bacteria.Eubacteria: CH3COOH2 ---> CH4 + CO2

Archaebacteria: CO2+4H2 ---> CH4 + 2H2O

2-(20)Biogenic methane

Methane formation


3. Maturity 3-(1)Production and decomposition of hydrocarbonDiagenesis; Catagenesis; Metagenesis(High molecular weight n-alkanes decrease by thermal degradation.)

Peak of oils at about 2500m: an average on Mesozoic and Paleozoic source rocks

The depth changes due to type of kerogen, burial history andgeothermal gradient.


3-(2) Diagenetic change in chemical structure of kerogen

Characterized based on some commonfanctional groups. “Infrared spectra”

Aliphatic bondsC-H (2920 and 2855 cm-1),CH2 (1375cm-1)CH3 (1455 and 1375 cm-1)

Aromatic bondsC-H (930-700 cm-1)C=C (1630 cm-1)

Ketones, acid and estersC=O (1710 cm-1)

These peaks decrease with increasing diagenesis mostly by temperature.


3-(3) Vitrinite reflectanceVery popular maturation indicator

Ro (%): 0.5, 1.0, 1.5, 2.0Tmax (℃): 435, 450, 470, 510

TypeIII&Humic coals

Measured on the polished vitrinite with oil at 546nm incident light under microscope

Based on the change in the reflectance of polished viriniteparticlesIncrease with increasing time and temperature (by progressive aromatization)

Abbreviations: Ro (o: in oil); %Ro; Rm (m: mean); Rmax; Rmin


homohopanesaverage equilibrium ratiosC31, C32, C33, C34, and C35 are 0.55, 0.58, 0.60, 0.62 and 0.59 (Zumberge, 1987)

22R and 22S C31-35 homohopanes20R and 20S C29 steraneC31 or C32 homohopanes22S/(22S+22R) ratio: 0 to about 0.6

3-(4) Maturity indicator of biomarker


3-(5) GC/MS SIM of oilsBiomarker: broken by thermal cracking and aromatization

17α-hopane decreases with increasing maturityThe less stable Tm decreases relative to Ts with increasing maturity. The C19-C29 tiricyclic terpanes can be used as fingerprint.

C27 hopanesTs/Tm; Ts is C27 18α-trisnorhopane (18α-22,29,30-trisnorhopane) and Tm is C27 17α-trisnorhopane (17α-22,29,30-trisnorhopane) and less stable than Ts.



3-(6) Maturity parametersThe ratio of 20S/(20S+20R)-C29-steranes: a good linear correlation with ßß(ßß+αα)-C29-steranes

αα means:C29- 14α, 17α(H)-sterane

ßß means:C29- 14ß, 17ß (H)-sterane

ßß(ßß+αα)-C29-steranes:From near-zero to about 0.7 (equilibrium at 0.67-0.71;seifert and Moldowan, 1986).

20R or 20S

17α or 17ß

14α or 14ß

3-(7)Different isomerization rate(diagenesis to catagenesis)

In low maturity:Hopane isomerizationincreases faster than sterane.

In high maturity:Hopane isomerizationincreases more showly than sterane.

Each maturity value does not indicate the exactly same stage of maturity under a different heating rate condition.



3-(8)Aromatic compounds are useful as a maturity indicator inpostmature zone.

Methylphenanthrene index (MPI):Radke et al (1982), Radke (1988) and Farrington et al (1988)

Based on the thermodynamic stability; ß-position is more stable than α-position.

MPI-3Sampei et al. (1994)

Ro=0.79*MPI-3-0.30(Ro=0.4-1.6).

Peters et al. (2005)3-(9)Range of maturity parameter20S/(20S+20R) steranes,22S/(22S+22R) hopanes:

up to 0.8 and 0.55 in %RoDia/(Dia+Reg) steranes,Ts/(Ts+Tm):

up to 1.4 in %Ro(Dia/(Dia+Reg) steranes have a disadvantage that is influenced by depositional environment and clay catalyst and Ts/(Ts+Tm) depends on source.)MA: mono-aromatic steroidTA: triaromatic steroidEtio: Etio-porphyrin is thermally derived from DPEP, DPEP:deoxo-phylloerythro-ethi-prophyrin.


Thermogenic methaneδ13C more than -50 ‰ vs PDB

low C1/ΣCn down to 0.6.

δ13C value of methane increase with increasing maturity by thermal cracking up to -20 ‰ vsPDB.

3-(10) Origin of methanebiogenic or thermogenic

Biogenic methaneδ13C about -60 to -80 ‰ vs PDB

very high C1/ΣCn more than 0.97

Cross plots of δ13C to methane/total hydrocarbon (C1/ΣCn)


4-(1)Primary migration:Migrate up or down to such a

porous and permeable carrier rock as sand stone

The driving force is an internal pressure due to inorganic and organic transformations.

Secondary migration:From the source rock through

permeable rocks along faults and conduits to trap

Great migration distance in the order of 100km unless special big unconformity

4. Migration and Trap


4-(2)Porosity and fluid pressure

Interrelationship of:Porosity of source rocks, Fluid pressure,Temperature,Depth

Primary migration efficiencies of between 5 and 80 % of available oil are believed.


4-(3)Porosity and permeability of reservoir rock

Reservoir rocks require more than:

10 % (porosity) and 1 m-darcy (permeability).


Then, the microfractures connect to initial fractures to migrate hydrocarbons.

4-(4)Microfracturing system in primary migration

Many microfractures are produced by overburden pressure after petroleum generation in catageneticstage.

Tissot and Welte (1984) 4-(5)Diffusion-controlled processes in primary migration

Hydrocarbons move independently from places of higher concentration to places of lower concentration.

For this diffusion system, important geological structures are:fractures, fault, and interbedded siltstone lens.

Tissot and Welte (1984) 4-(6)Molecular solution in water

One of possible transporting mechanism of petroleum during primary migration

Generally low molecular weight hydrocarbons are more water-soluble than high molecular weight hydrocarbon.

For n-alkane, water-solubilitylogarismically increases with decreasing carbon number.

Aromatic compounds are more water-soluble than n-alkane.High temperature increases water-solubility of hydrocarbon.Molecular solution system in primary migration is important for low molecular weight hydrocarbon.


4-(7)Molecular solution in gas

Solubility of petroleum in gas increases with increasing pressure and temperature.


Large faults make complex for oil trap system.

4-(8) Complex system for oil accumulation

Major boundary fault acts as primary conduit for migration.


4-(9) Preferential expulsionCompositional fractionation sometimes occurs due to petroleum expulsion, which is recognized by comparing n-alkane distribution ofbitumens from thick and thin source rock formations.

Thin source rocks easily expelled light molecule n-alkane. The lighter molecular weight is, the more hydrocarbon is expelled, according to the n-alkane distribution from the thick ones.


5-(1)Standard evaluation sheet for source rock potential

TOC,Rock-Eval S1,S2HIOI%RoTmaxBiomarker compositions

For considering:Kerogen typeDepositional environment,Hhydrocarbon potentialMaturity

5. Source Rock Evaluation


To assess the source rock generative potential, the most basic parameters are TOC and S2.

More than 1% of TOC and 5mgHC/g-rock is a good source rock, and less than 0.5% of TOC and 2.5mgHC/g-rock is a poor source rock.

5-(2) Source rock generative potential


Generally, many shales are not so rick in TOC and S2.The peaks of TOC and S2 are sometimes about <1% and <2.5%. Nevertheless, very high TOC and S2 more than 5% and 20mgHC/g-rock, respectively, are occasionally interbedded in the shales and sand. We need to know thickness, age, depositional environment, continuity and maturity

5-(3) TOC and S2 of shales

Ibach (1982)

5-(4) Controlling factors of TOC

Primary productivityOxic-anoxic conditionSedimentation rate

Sedimentation rate is often a key.

Ibach (1982)

Up to about 0.1mm/yTOC increases with increasing SD.

Over about 0.1mm/yTOC decreases with increasing SD.


5-(5)S2-TOC plot

S2-TOC plot is a useful evaluation diagram for source rock. On this diagram HI levels which show kerogen type are expressed as a linear line.

Source rocks are sometimes plotted on the straight line with an intercept zero, indicating that the source rock had deposited under the same environment and composed of same type kerogen.


5-(6)Lacustrine source rock evaluation

Coal deposits under the condition with high sediment+water influx and low accommodation rate, i.e. in the fluvial system with over filled.

Type I kerogen may deposit under the condition with high sediment+water influx and high accommodation rate with high primary productivity in the balanced fill system


Steranes and hopane distributions are good indicators for organic source.

5-(7) Biomarker as organic source indicator


5-(8)Biomarker as organic source indicator 1

Ternary diagram of C27-C28-C29-steranes shows origins of organic matter;

C27-sterane is mainly fromphyto-plankton.

C28-sterane is mainly from such specific plankton as diatom.

C29-sterane is mainly from land-plant.


5-(9)Age control of the C28/C29steranes ratio

Care should be paid for the interpretation of C28/C29steranes ratio.

Because C28/C29 sterane ratios have changed during the last 600 Ma.

The ratio from marine source rock with a little or noterrigenous organic matter input have increased from about 0.3 in 600Ma to 1.3 in 100 Ma


5-(10) Oxic-anoxic proxy 1Oxic-anoxic proxy: pristine/phytane (Pr/Ph) ratio.

High Pr/Ph ratios >3.0 indicate terrestrial organic matter input under oxicconditions and low values <0.6 typify anoxic (Peters and Moldowa, 1993).


5-(11) Depositional environment indicator

10*Gammacerane/(Gammacerane+Hopane) showing oxic-anoxic condition according to salinity stratification .

(water-colum stratification, commonly due to hypersalinity)


5-(12) Origin indicator

Highly branched isoprenoids(HBI) are diatom markers(Jurassic to Tertiary)HBIs:series of C20, C25, C30,C35


5-(13) Depositional indicatorIsoprenoid thiophenes:Anoxic and iron-poor condition produce H2Sby sulfate reducing bacteriaThen H2S was incorporated into isoprenoids.


5-(14) Origin indicator 2

Irregular isoprenoid hydrocarbonbotryococcne (C34H70) is fromBotryococcus braunii.

A lacustrine alga accumuratedinto boghead coal and torbanite


5-(15) Origin indicator 3

Oreanane is from angiosperms or flowering plants nearlyterrigenous mainly after Cretaceous age.

Oleanane/(Oleanane+C30hopane) ratio:Highly specific for higher plant input

Stanford Report, April 4, 2001

Geochemists find evidence that flowers may have evolved 250 million years ago

When flowering plants appeared on Earth ?

According to the fossil record, flowering plants abruptly appeared out of nowhere about 130 million years ago.

"Flowering plants may have originated during the Permian period, between 290 and 245 million years ago. We based our findings on an organic compound called oleanane " says J. Michael Moldowan, research professor of geological and environmental sciences.

Oleanane Oleanane is produced by many common flowering plants as a defense against insects, fungi and various microbial invaders. But the chemical is absent in other seed plants, such as pines and gingkoes.

Gigantopterids:The oldest oleanane-producing seed plants, concludes biologist David Winship Taylor of Indiana University Southeast.

Gigantopterids, an extinct plant group that lived some 250 million years ago, may be the oldest relatives of roses, daffodils and other flowering plants.

Fossilized deposits of gigantopterids containoleanane – an organic chemical found in modern flowering plants but absent in pines and other seed plants.

This drawing is a reconstruction of Vasovinea tianiia, a species of gigantopterid unearthered in China in 1993.

Artist: Hongqi Li/American Journal of Botany

Mosses were the first plants to emerge on land some 425 million years ago, followed by firs, ginkgoes, conifers and several other varieties.

http://www.stanford.edu/dept/news/report/news/april4/acsflowers-44.html


Iron and magnesium are bonded to these compounds.

While, during diagenesis ion exchange takes place in the nucleus, and nickel and vanadium are substituted.

Organometallic derivatives of the nucleus of the haeminor chlorophyll molecule.

5-(16) Porphyrin


During transgressive, TOC and HI are high, and terrigenous input and degradation are low.

5-(17) Souce rock potential and environmental change


Oil-Oil correlation:n-alkane, aromatics, biomarker, isotope ratio

Oil-Source rock:n-alkane, aromatics, biomarker, isotope ratio

Oil-Gas:light n-alkane, isotope ratio

Gas-Gas: light n-alkane, isotope ratio

Gas-Source rock:n-alkane, isotope ratio

6. Oil-Source Rock Correlation and biodegradation

6-(1)Tool for oil-source rock correlation

Curiale (1993)

6-(2) Correlation by n-alkane

n-Alkane distribution is useful for correlation.

Between bitumensfrom source rock and oils

Curiale (1993)

6-(3) Correlation by steranes and hopanes

Steranes and hopanes are the most useful fingerprints.

Care should be paied to the maturity.


6-(4)Correlation by steranes

Comparing the ternary diagrams of sterane and diasterane

Diasterane composition reflects rock faces such as clay stone.


6-(5)Confidence of oil-source rock correlation

Under marine and lacustrine environment, the oil-source rock correlation may be known.

The gas – source rock correlation is difficult under deltaic and coal-forming condition


6-(6)Biodegradation of n-alkane

n-Alkane is the most sensitive to biodegradation.

Higher molecular n-alkanes are easily broken in the first stage of biodegradation


6-(7)Biodegradation stage

Hydrocarbon gases→ n-alkanes→ iso-alkanes → isoprenoids → aromatics → poly-aromatics → steranes&hopanes


6-(8) Biodegradation effect on sulfur&nitrogen contents and APISulfur and nitrogen contents decrease about 4 and 0.6% to 1 and 0.1%, respectively.While, API increases from about 8 to 30

7-(1)Changes in %Ro under different heating rate

With increasing heating rate, maturity of the peak of oil window decreases: %Ro=0.9 at <1ºC/Ma, %Ro=0.75 at 1-2ºC/Ma, %Ro=0.6 at 6ºC/Ma.

Therefore, computer simulation is necessary for an accurate discussion

Rullkotter (1993)

7. Modeling

Geothermal gradient (℃/km)

Depending upon 1. thermal conductivity of rock strata,2. heat flow 3. water movement

World average:25℃/km5℃/km: ex. Andros Island in the Bahamas

90℃/km: ex. Walio oilfield in the Sarawati Basin, indonesia

Heatflow(Q) Q=k×ΔTk:thermal conductivityΔT:geothermal gradient

1 (HFU: heatflow unit) = 0.42×10-5 (Wm-2)World average: 0.63×10-5 (Wm-2)

q

dtdT

=

)( qtT=

∆∆

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (3 )

dTe

qAk RTET

T

/

0

−∫= - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (4 )

+−= − 2/

2

)(6)(21)(E

RTE

RTeqE

ARTk RTE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (5 )

))1((/)(/2

/1

111 ;;; TnTREn

TTRERTE AekAekAek ∆−+−∆+−− =⋅⋅⋅⋅⋅⋅⋅⋅== - - - - - - - - - - - - - - - - - - - - - - - - (6 )

tk

nntktk neCCeCCeCC ∆−

−∆−∆− =⋅⋅⋅⋅⋅⋅⋅== 11201 ;;; 21

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ( 7 )

tkkk

nneCC ∆+⋅⋅⋅⋅⋅⋅++−= )(

021

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (8 )

kteCC −= 0 ( c o n c e n t ra t io n c h a n g e ) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (1 )

RTEAek /−= (A r rh e n iu s e q u a t i o n ) - - - - - - - - - - - - - - - - - - - - - - - (2 )

q

dtdT

=

)( qtT=

∆∆

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (3 )

dTe

qAk RTET

T

/

0

−∫= - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (4 )

+−= − 2/

2

)(6)(21)(E

RTE

RTeqE

ARTk RTE - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (5 )

))1((/)(/2

/1

111 ;;; TnTREn

TTRERTE AekAekAek ∆−+−∆+−− =⋅⋅⋅⋅⋅⋅⋅⋅== - - - - - - - - - - - - - - - - - - - - - - - - (6 )

tk

nntktk neCCeCCeCC ∆−

−∆−∆− =⋅⋅⋅⋅⋅⋅⋅== 11201 ;;; 21

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ( 7 )

tkkk

nneCC ∆+⋅⋅⋅⋅⋅⋅++−= )(

021

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (8 )

kteCC −= 0 ( c o n c e n t ra t io n c h a n g e ) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (1 )

RTEAek /−= (A r rh e n iu s e q u a t i o n ) - - - - - - - - - - - - - - - - - - - - - - - (2 )

Sampei and Suzuki (2005)

7-(2) Kinetics of isomerization Activation energy (E); Pre-exponential factor (A) C: concentration of kerogen, C0: initial concentration of kerogen, k: rate constant, t: time, A: pre-expornential factor, E: activation energy, R: gas constant 1.987 cal/deg, T: absolute temperature, q: heatig rate, (5) by Alexander et al. (1986)


7-(3) Data set of kinetic parmeters


7-(4) Simulation results


La Cira 1625K well, Colombia

Modeling of Burial History for the La Luna Formation(Well)

Age m.y

Cretaceous

by PRA software

La Cira 1625K well, Colombia

Cretaceous

Age m.y

by PRA software

organic geochemistry 06

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