new heating rate dependency of petroleum-forming reactions: …directory.umm.ac.id/data...

Heating rate dependency of petroleum-forming reactions:implications for compositional kinetic predictions

V. Dieckmann a,b,*, B. Hors®eld a, H.J. Schenk a

aInstitut fuÈr ErdoÈl and Organische Geochemie (ICG-4), Forschungszentrum Juelich GmbH,

D-52425, JuÈlich, GermanybENI div. AGIP Spa, 20097 San Donato Milanese, Milan, Italy

Abstract

The generation of bulk petroleum, liquid and gaseous hydrocarbons from the Duvernay Formation was simulated

by heating immature kerogens in a closed system (MSSV pyrolysis) at four di�erent heating rates (0.013, 0.1, 0.7 and5.0 K/min). Using the established parallel reaction kinetic model, temperature and compositional predictions weretested to be suitable for geological conditions by comparing the laboratory results with natural changes in source

bitumens and reservoir oil maturity sequences from the Duvernay Formation. In the case of bulk liquid and gaseoushydrocarbons, the above kinetic calculations can be considered valid because their maximum yields are independent oflaboratory heating rates. In contrast, the contents of para�ns, aromatics and sulfur compounds show a pronouncedheating rate dependence. Extrapolated to geological heating rates, the compositional predictions are consistent with the

bulk composition of natural products in the Duvernay-petroleum system showing an increase of para�nicity andhydrogen content. In contrast to that, the ``hump'' decreases with decreasing heating rate, a trend which is con®rmedby the low amounts of unresolved compounds in natural high maturity products. Because of these heating-rate

dependent compositional changes, geological predictions of natural molecular composition by the commonly usedkinetic models are not suitable. # 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Duvernay Formation; Bulk kinetics; Compositional kinetics; Aromaticity; Heating-rate dependency

1. Introduction

Diagenesis, catagenesis and metagenesis are the threeconsecutive alteration stages of the carbon cycle; irre-

versibly changing the composition of sedimentaryorganic matter. Petroleum formation takes place mainlyin the second and third stages, leading to the formation

of oil/gas and gas, respectively (for review, see Hors®eldand RullkoÈ tter, 1994). While petroleum-forming reac-tions are exceedingly complex and unknown in detail, it

is clear that cracking, aromatisation and condensationare all involved in maturation processes leading to theformation of an organic hydrogen-rich volatile fraction

which may then migrate from the source rock and theorganic hydrogen-poor solid residues which remainbehind. Pressure exerts a strong in¯uence on the prop-erties of the solid residues, as exempli®ed by the bire-

¯ectance of vitrinite (Carr and Williamson, 1990), but asfar as the actual generation of petroleum from kerogenis concerned, temperature is generally considered to bethe main driving force (Philippi, 1965; Louis and Tissot,

1967; Burnham and Singleton, 1983; BeÂ har and Van-denbroucke, 1996; Michels et al., 1995; cf. Price andWenger, 1992).

Because temperature is the main driving force of pet-roleum generation, laboratory pyrolysis is used routi-nely to simulate the process. For instance, Rock-Eval S2

and Hydrogen Index values predict petroleum yields asa function of kerogen type and maturity (Larter, 1984;Pelet, 1985; Cooles et al., 1986; Espitalie et al., 1988)

and pyrolysis-gas chromatography can provide infor-mation on petroleum type (for review, see Hors®eld,1997). Similarly, and especially pertinent to the presentarticle, the kinetics of product generation calculated for

kerogen pyrolysis are used to predict the rate and timingof petroleum generation in sedimentary basins (Tissot,1969; Tissot et al., 1971; Burnham et al., 1987; Ungerer

0146-6380/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.

PI I : S0146-6380(00 )00105-4

Organic Geochemistry 31 (2000) 1333±1348

www.elsevier.nl/locate/orggeochem

* Corresponding author.

E-mail address: [email protected] (V. Dieckmann).

and Pelet, 1987; EspitalieÂ et al., 1988; Braun and Burn-ham, 1990; Schaefer et al., 1990; Ungerer, 1990; BeÂ haret al., 1992; Schenk and Hors®eld, 1993; Dieckmann etal., 1998). The underlying assumption in all of these

methods is that the reactions occurring in nature areclosely similar to those brought about by pyrolysis,despite at least 10 orders of magnitude di�erence in

heating rate. Criticisms of this assumption have beenvoiced for speci®c cases by Lewan et al. (1995), Muscioand Hors®eld (1996) and Schenk and Hors®eld (1998),

because the role of cracking can be overemphasisedrelative to aromatisation and condensation in labora-tory (anhydrous) pyrolysis. Nevertheless, it remains a

fact that kinetic modelling is a routine part of petroleumexploration and that laboratory predictions are good,given the uncertainties in kerogen type distribution andtemperature histories in natural settings (Quigley et al.

1987; Ungerer and Pelet, 1987; Braun and Burnham,1990; Burnham et al., 1995; Pepper and Corvi, 1995;Schenk and Hors®eld, 1998).

The current contribution is concerned with the reac-tion kinetics of petroleum formation at the molecularlevel (compositional kinetics). Most kinetic models

assume a ®xed number of parallel reactions (or Gaus-sian distribution), each of which is assumed to be of®rst-order (e.g. Tissot, 1969). Predicting petroleum

compositions, rather than bulk yields, is importantbecause the initial gas±oil ratio of expelled petroleumstrongly in¯uences the phase state (unsaturated oil, gas-saturated oil with gas cap, gas with dissolved con-

densate) and hence the volume of that petroleum as itmigrates through carrier systems as pressure and tem-perature gradually fall. EspitalieÂ et al. (1988) used an

open pyrolysis system with selective trapping to deter-mine the kinetic parameters of primary (direct fromkerogen) C2ÿ5, C6ÿ14 and C15+ products from type II

and type III kerogen from the Viking Graben. Closedsystem experiments have since been employed to simu-late both primary and secondary (e.g. oil -> gas)cracking reactions (Braun and Burnham, 1990; Ungerer

1990; BeÂ har et al., 1992, 1995; Hors®eld et al., 1992;Schenk and Hors®eld, 1993; Schenk et al., 1997; Dieck-mann et al., 1998). Using open and closed system pyr-

olysis con®gurations, BeÂ har et al. (1997) and BeÂ har andVandenbroucke (1996) have applied the kinetic conceptof the parallel reaction model to di�erent hydrocarbon

fractions. Finally, Tang and Stau�er (1995) and Tangand BeÂ har (1995) used exclusively single compounds fortheir kinetic evaluations; ®nding out that these kinetics

and resulting temperature predictions are closely similarto those from bulk kinetics. Compositional kinetic pre-dictions are di�cult to validate because the success ofthe prediction can only be assessed by studying product

distributions, unlike bulk kinetic predictions which canbe tested using residues. Their value therefore remainsuncertain.

The aim of this paper is to consider predictions of pet-roleum composition with reference to reaction mechan-isms in nature versus the laboratory, and the utility ofsimple parallel reaction models. The e�ect of heating rate

is a notable issue because, to be valid, reaction modelsshould not be rate-dependent, and yet earlier works fromVan Heek (1982) on coals, Burnham and Happe (1984)

and Burnham and Singleton (1983) on oil shales andHors®eld (1997) on petroleum source rocks, havedemonstrated that the observed yields of alkanes, aro-

matics and NSO compounds are strongly heating-ratedependent. However, total yields, at least in the case ofmarine source rocks and oils, are not heating-rate

dependent (Schenk and Hors®eld, 1993; Dieckmann etal., 1998). Here, we report the results of simulationexperiments under open and closed system pyrolysisconditions on samples from the Duvernay Formation,

Western Canada Basin. A natural sample set from theDuvernay Formation (reservoired oils and source rocksamples) was used to calibrate the compositional evolu-

tion of arti®cially generated products in order to show ifrespective compositional kinetic evaluation is realistic.

2. Materials and methods

2.1. Sample origin

The upper Devonian Duvernay Formation is one ofthe most proli®c marine source rocks in the Western

Canada Sedimentary Basin (WCSB). It contains pri-marily type II kerogen and is thought to be the source ofoil and gas reservoirs in the Leduc and Nisku reservoirs

along the Rimbey-Meadowbrook reef trend in centralAlberta (Creaney and Allan, 1990) (Fig. 1). The mainhydrocarbon formation phase from the Duvernay For-

mation is thought to be linked to a subsidence phaseassociated to the Laramide orogeny. According toStoaks and Creaney (1984, 1985) and a more recent studyof Chow et al. (1995) two basic lithofacies units can be

recognised within in the Duvernay Formation; Litho-facies 1, dominated by nodular to nodular-banded limemudstones, exhibits varying degrees of bioturbation and

was deposited under relatively oxygenated (dysoxic)conditions. Lithofacies 2 is consisted of laminated limemudstones (up to 14% TOC) and was deposited in deep

water oxygen-starved euxinic conditions. Li et al. (1998)have illustrated that these lithofacies are manifested incomposition of the Leduc oils.

In the study area (Fig. 1), it is known that theDuvernay Formation covers a maturity range from veryimmature in the north to overmature in the south(Stoaks and Creaney, 1984). Reservoirs ®lled by the

Duvernay Formation's products are dominated by oilentrapments in the shallower northern reef systems,while the deep seated reservoirs in the south are ®lled by

1334 V. Dieckmann et al. / Organic Geochemistry 31 (2000) 1333±1348

high maturity gas/condensates (Fig. 2). The source rocksample set selected for this study covers the completematurity pro®le (Table 1), as does the suite of reser-

voired oils with API gravities in the range 36 to 52�

(Table 2). From a molecular point of view, this broadmaturity range is also re¯ected by the MPT±2-ratio

(Radke et al., 1980) which shows a clear increase up toan API-gravity of 46 and then decreases again in thehigher maturity oils (Dieckmann, 1998). The crude oilswere reported not to be a�ected by migration phenom-

ena (Li, unpublished).

3. Experimental approach

After solvent extraction using ¯ow-blending (dichlor-

omethane, 15 min; Radke et al., 1978), each source rocksample from the maturity sequence was pyrolysed underopen-system conditions and the kinetic parameters of

bulk petroleum formation were calculated from the ratecurves (Schaefer et al., 1990). After normalisation toinitial carbon (immature stage) (Pelet, 1985; Schenk andHors®eld, 1998), the rate curves were overlain in order

to ascertain whether facies variations were present andto verify that the main reaction pathway was that ofcracking rather than aromatisation/condensation (Schenk

and Hors®eld, 1998). This also allowed the most suitableimmature sample to be selected for closed system pyr-olysis experiments. The kinetic parameters of primary

and secondary gas generation were calculated from theclosed system pyrolysis data. Additionally, detailedcompositional data from the experiments were com-

pared with thermovaporisation data from the naturalsource rock maturity sequence and with whole oil gaschromatograms. Experimental details are given below.

3.1. Open system bulk ¯ow pyrolysis±FID

100 mg of each ®nely ground sample were pyrolysed

at heating rates of 0.1, 0.7 and 5.0 K/min using a fur-nace set up described by Schaefer et al. (1990).Temperatures were measured by a thermocouple located

immediately above the sample. A constant ¯ow of argon(45 ml/min) was maintained in order to transport allpyrolysis products to the ¯ame ionisation detector for

the continuous registration of bulk formation rates.

3.2. Closed system (MSSV) pyrolysis±gaschromatography

The principles of microscale sealed vessel (MSSV)pyrolysis have been described by Hors®eld et al. (1989).

Fig. 1. Location of sampled wells in the Alberta Basin. *, Source rock sampling;*, oil sampling). The regional maturity distribution

is based on source rock screening by Rock-Eval and TOC (modi®ed from Stoaks and Creaney, 1985).

V. Dieckmann et al. / Organic Geochemistry 31 (2000) 1333±1348 1335

For the current study, 90 aliquots of immature kerogenconcentrate (isolated according to the method of Dur-and, 1980) were sealed in glass capillary tubes and pyr-

olysed in batches to selected temperatures at threeheating rates (0.1, 0.7 and 5.0 K/min) within a massivecylindrical brass block which served as sample holder.For a selected number of analyses, lower heating rate

(0.013 K/min) was also used. Temperatures were mea-sured with a thermocouple located in the brass blockwhere the temperature errors during the heating pro-

grams were <0.1�C. To obtain an accurate databaseinvolving enough samples for the primary formation aswell as for the secondary cracking temperatures, the

®nal temperatures in this study were in the range of540±610�C. The composition of oil and gas formed ineach tube was determined by a single-step on-line gas-

chromatographic analysis. An HP-1 column (1.65 mm®lm thickness, 25 m�0.31 mm i.d.) connected to a ¯ameionisation detector was used, employing helium as car-rier gas. The GC oven was programmed from ÿ10�C (2

min isothermal) to 320�C at 8�C/min. The major indi-vidual components were quanti®ed (n-alkanes, aromatichydrocarbons and thiophenes), as were boiling ranges

(C1ÿ5, C6ÿ14, C15+). The latter included both resolved and

unresolved components in the respective ranges. Aromati-city was calculated as the ratio of the sum of benzene,toluene, xylenes, ethylbenzene, naphthalene, methyl-

naphthalenes and dimethylnaphthalenes to the sum of theC6+ n-alkanes. The quanti®cation of the products wasperformed using n-butane as external standard.

3.3. Kinetic model

The mathematical model has been described by

Schaefer et al. (1990). It is based on the kinetic analysisof formation rate �dM=dT� vs. temperature (T) curvesassuming twenty ®ve ®rst order parallel reactions with

activation energies Ei regularly spaced between 46(192.7) and 70 (293.3) kcal/mol (kJ/mol) and a singlepre-exponential factor A. A total number of 26 para-meters, namely 25 potentials (partial yields) associated

with 25 activation energies and the pre-exponential fac-tor A were optimised by a least squares iterationmethod that compares measured and calculated forma-

tion rates at 600 temperatures (200 per heating rate)until the corresponding error function (sum of squareddi�erences) presented a well-de®ned absolute minimum.

In the case of open system pyrolysis, the curves weremeasured directly. As described by Hors®eld et al.(1992), rate curves for MSSV data were generated by

placing a spline through measured cumulative datapoints and then di�erentiating the curve.

3.4. Thermovaporisation±gas chromatography

The gas chromatographic analysis of freely occurringvolatile organic matter in the source rocks and crude

Table 1

List of Duvernay rock samples and related rock TOC and

Rock-Eval data used in this study in order to establish a nat-

ural source rock maturity sequencea

Well Sample Tmax HI TOC MPI 2 GOR

RED-2 42714 414 543 6.24 0.23 0.05

TOM 42721 415 520 6.09 0.11 0.06

42725 428 599 7.56 0.92 0.1

LE 42728 433 578 7.91 0.67 0.03

42731 436 575 4.47 0.8 0.05

42732 436 580 5.14 0.82 0.07

NOR 42735 464 37 3.56 1.88 0.02

42736 465 40 4.36 1.82 0.01

FOB 42738 442 385 9.71 0.71 0.02

42739 443 419 10.3 0.72 0.04

42740 442 364 10.7 0.77 0.01

42742 436 292 1.65 0.76 0.02

IMP3 42748 427 547 5.05 0.83 0.08

IMK 42765 423 527 5.01 0.49 0.04

FEB 42768 436 271 4.31 0.86 0.01

42769 437 273 4.02 7.2 0.01

42771 437 304 4.88 0.78 0.01

IMC 42777 771 303 4.19 1.5 0.05

42779 450 100 3.44 1.4 0.01

SAP 42786 418 551 6.9 0.7 0.03

42787 419 517 7.33 0.91 0.04

42790 420 604 8.58 0.39 0.03

BARR 42797 548 2.46 5.63 0.22 0.02

BI 42802 425 609 10.9 0.39 0.11

CAM 42807 430 450 2.25 0.62 0.02

42810 424 645 10.7 0.72 0.13

42811 425 611 4.84 1.09 0.06

a The locations of related wells are given in Fig. 1.

Table 2

List of reservoired oil samples used in this study in order to

establish a natural maturity sequence of reservoired oils gener-

ated from the Duvernay Formationa

Sample Well API MPI 2

East-shale basin

E44684 LW1 38 1.02

E44686 RED 36 0.81

E44687 HR 44 1.14

E44692 LW2 37 0.99

West-shale basin

E44691 JC 39.5 1.02

E44685 Nisku-S 52.36 1.77

E44688 Nisku-D 39.37 2.49

E44689 Nisku-Q 47.1 2.38

E44690 Nisku-J 53.6 1.77

a The molecular maturity index MPI 2 is shown in order to

illustrate that the changes in API gravity are related to the

molecular maturity of the oils. The locations of related wells

are given in Fig. 1.


oils was performed without prior liquid chromato-graphic separation by means of the MSSV pyrolysisinstrument described above. Rocks were only coarselycrushed to minimise evaporative loss prior to sealing in

the capillary tubes. Crude oils were injected onto pre-cleaned quartz wool within the tubes and the tubes thensealed (Schenk et al., 1997). Volatile materials were

released from the tubes by cracking them open at 300�C,and analysed under the same conditions as describedabove for MSSV pyrolysis.

4. Results and discussion

4.1. The natural maturity sequence

In an earlier study (Schenk and Hors®eld, 1998), we

showed that petroleum generation from the PosidoniaShale both in nature and during simulated maturationresulted mainly from cracking reactions, and therefore

that petroleum generation over geological time could bereliably extrapolated from pyrolysis of the appropriateimmature sample. By contrast, signi®cant deviations

were observed between the natural and arti®cialcoali®cation series of vitrains, inferring that petroleumgeneration could not be reliably extrapolated fromopen-system pyrolysis of the appropriate immature

sample. The main criterion for distinguishing thesedi�erent behaviours was the temperature envelope ofthe matured samples relative to that of the least mature

sample, cracking being characterised by curves withinthe original envelope and aromatisation being char-acterised by curves extending beyond it. It was with thisin mind that the natural Duvernay series was evaluated

in order to establish whether laboratory pyrolysis wasindeed the best way of determining kinetic parametersfor petroleum generation.

As described above, three heating rates wereemployed for bulk kinetic analysis of the Duvernaymaturity sequence. Fig. 3 shows the bulk hydrocarbon

formation-rate curves (mg/g*K) for 0.1 K/min experi-ment after normalisation to initial carbon (Schenk andHors®eld, 1998). The well abbreviations and Rock-EvalTmax values are from Table 1. It is clearly seen that the

curve maxima are shifted to higher temperatures withincreasing maturity. This is thought to be a result of theongoing elimination of the labile parts of the kerogen

structure. The end-temperature of generation is aboutthe same for all samples and there is no major shift ofhydrocarbon formation curves to temperatures exceed-

ing the envelope de®ned by the least mature sample.We conclude from the foregoing that the main pro-

cesses leading to the formation of hydrocarbons from

the Duvernay Formation in nature are characterized bythermal cracking of chemical bonds in the kerogenstructure, rather than aromatisation and condensation.This means that geochemical data for this sample series

can be directly compared with the results of simulatedmaturation, a process considered to proceed via mainlycracking reactions.

Fig. 2. Geological pro®le through the Rimbey-Leduc-Meadowbrook reef-system showing the distribution of oil and gas reservoirs

®lled by Duvernay products (Stoaks and Creaney, 1985).


Sample LED is slightly anomalous in that its curve

extends beyond the others, and is possibly attributableto a more stable kerogen type. However, this is rela-tively minor, especially when compared with the big

shifts displayed by Carboniferous coal with increasingrank (Schenk and Hors®eld, 1998).Fig. 4 illustrates the activation energy distribution

and respective frequency factors calculated by thekinetic model. According to this ®gure, both frequencyfactors and dominant activation energies increase withincreasing maturity of the samples. In each case the

single frequency factor A of the kinetic model will besome kind of weighted average of the high and low fre-quency factors associated with high and low activation

energies (Burnham et al., 1995). This model frequencyfactor must increase along a maturation sequencebecause the samples become more and more depleted in

pyrolytic low-energy potentials as a consequence ofnatural generation. In going from the least mature(SAP) to the most mature Duvernay sample (IMC b),the value of A increases by about 60 times which is more

pronounced than the increase found for Toarcian Shalesin the maturity range of 0.48 to 1.44% Rr (Schenk andHors®eld, 1998). The increase of the average frequency

factor implies that low-energy potentials do not onlydecrease in the course of natural maturation (Tissot etal., 1987), but that they are shifted to higher activation

energies, because the relationship between A and theactivation energies and Tmax temperatures of individualreactions must be maintained,

E �individ:; mature�=�ln A�mature� ÿ ln r�

� E �individ:; immature�= �ln A�immature� ÿ ln r�

with ln r�0 for laboratory heating rates r. This e�ectgenerally enhances the maturity induced shift of poten-

tial versus activation energy distributions (Schenk andHors®eld, 1998).

4.2. The simulated maturity sequence Ð bulk

compositional predictions

Fig. 5a illustrates the cumulative evolution (mg/g

TOC) of C1ÿ5, C6ÿ14 and C15+ boiling ranges duringprogrammed-temperature closed-system (MSSV) pyr-olysis of the immature Duvernay Formation sample at

heating rates of 0.1, 0.7 and 5.0 K/min. In accordancewith the theory of non-isothermal kinetics, all evolutionpro®les are shifted towards higher temperatures with

increasing rate of heating. The apices of the cumulativeC6ÿ14- and C15+-evolution curves mark the tempera-tures where degradation processes exceed primary for-mation processes.

Fig. 5b shows the cumulative formation of C6+ andC1ÿ5 fraction at three laboratory heating rates (0.1, 0.7and 5.0 K/min). The secondary formation of gas from

oil to gas cracking reactions in the Duvernay Formationpreviously was shown to start when the cumulative for-mation of C6+ compounds comes to an end (Dieck-

mann et al., 2000).The amount of secondary gas can therefore be calcu-

lated from the fall in yield below the maximum observed

value multiplied by a stoichiometric constant (Dieck-mann et al., 1998; also see Ungerer, 1990; Pepper andDodd, 1995). The result is shown in Fig. 6. Also shownis the yield of primary gas, generated directly from the

kerogen structure, calculated by subtracting the yield ofsecondary gas from total gas.Typically for marine source rocks, the pyrolysates

were dominated by the C6+ fraction, which make up to160 mg/g TOC. With 120 mg/g TOC, the primary gasformed directly from the kerogen dominates the total

gas composition at higher maturities, while 90 mg/gTOC of the generated gas can be related to the crackingof previously generated oil. Importantly, all boilingrange yields are the same, irrespective of heating rate, a

prerequisite for kinetic modelling.Two issues arise from the foregoing results, namely

the yields from closed system pyrolysis, and distin-

guishing primary from secondary reaction products forkinetic modelling.Firstly regarding yields, it is noteworthy that the

cumulative sum of all boiling ranges (C1ÿ5+C6ÿ14+C15+=C1+) amounts to about 200 mg/g TOC at allheating rates for this sample (SAP). This total closed-

system yield is considerably lower than the correspond-ing open-system Hydrogen Index of that sample (ca. 600mg/g TOC; Table 1). Lower yields from the MSSVcon®guration are not caused simply by di�erences in

mechanisms of open- versus closed-system pyrolysis.Indeed, bulk yields from both the open- and closed-system pyrolysis of Posidonia Shale and Duvernay

Fig. 3. Bulk petroleum formation rates (mg/g TOC) from the

natural maturity sequence of the Duvernay Formation at a

laboratory heating rate of 0.1 K/min.


Formation kerogens under the same analytical con®g-uration with GC-interface are identical (Dieckmann et

al., 1998, 2000). Rather, the di�erences in yield appeardue to very heavy pyrolysis products condensing in theGC-interface (irrespective of whether the experiment

was performed under open- or closed-system condi-tions) whereas they simply pass through (either intact orare cracked to smaller molecules) the high temperature

(550�C) split of the Rock-Eval and are detected by FID.It is obviously important to know what e�ect con-densation has on kinetic parameters. For instance, pro-duct rate curves for pyrolysis systems employing a GC-

interface (in this case, MSSV pyrolysates) should beskewed to higher mean temperatures if early-formedproducts were particularly enriched in materials of high

molecular weight that readily condense in the GC-interface. While this phenomenon cannot be ruled out

for all samples, it does not apply to the Posidonia Shale.For this source rock, we have already shown that thekinetic parameters of C1+ product generation (MSSV

pyrolysis) and total pyrolysate generation (bulk-¯owopen-system pyrolysis) are identical (Schenk and Hors-®eld, 1993). It does not seem to apply to the Duvernay

Formation either. While the kinetic parameters for C1+

generation (MSSV) have not been calculated for theanalysed Duvernay Formation sample, we note thatpredictions of C6+ product generation from the kinetic

model are closely similar to those for bulk-¯ow pyr-olysis (see below). These cases strongly argue that theproportion of heavy condensable pyrolysate is constant

Fig. 4. Activation energy distributions (kcal/mol) and frequency factors (1/min) of Duvernay samples at di�erent levels of maturity.

The kinetic evaluation was performed on the basis of open system pyrolysis at three di�erent heating rates (0.1, 0.7 and 5.0 K/min).


for each of the pseudo-reactions of kerogen pyrolysis, andthat kinetic predictions from theMSSVmethod are valid.Secondly, the simplistic di�erentiation of primary and

secondary reaction products needs justifying. In Fig. 5a,total gas yields converge to a plateau at higher tem-peratures and remain there because any cracking of wet

gas components is compensated by the enhanced gen-eration of methane. By contrast, the concentrations ofall liquid compounds ®rstly increase and then decreaseas a consequence of secondary cracking which over-

compensates primary generation at higher temperatures.From the evolution pro®les of total C6+ compounds(=C6-14+C15+; Fig. 5b) the predominance of second-

ary oil cracking over primary oil generating reactionsbecomes obvious at temperatures exceeding 405�C (0.1K/min), 430�C (0.7 K/min) and 460�C (5.0 K/min). It is

quite impossible to deconvolute a measured generationcurve into primary and secondary curves in a reliablemanner. For the purpose of kinetic modelling we have

therefore assumed that the overlap between primary andsecondary reactions can be neglected, the latter operat-ing only when the former have come to an end. Thevalidity of this fundamental assumption has already

been veri®ed for the Duvernay Formation by comparingC6+ evolution under closed (MSSV) and open (Py-GC)conditions (Dieckmann et al., 2000), using the same

Fig. 5. Cumulative formation (mg/g TOC) of the (a) C1ÿ5, C6ÿ14 and C15+ and (b) C1ÿ5 and C6+fractions during closed MSSV-pyr-

olysis at three heating rates (0.1, 0.7 and 5.0 K/min).


analytical con®guration and employing a GC-interface.Consequently, yields of secondary gas could be calcu-lated from the decrease of C6+ concentrations accord-

ing to the procedure outlined by Dieckmann et al.,(1998). Furthermore, because open- and closed-systemC1+ yields from these experiments are essentially iden-

tical throughout the entire range of pyrolysis tempera-tures (350±540�C), all primary and secondary sources ofmeasured gas yields have been taken into account.The resulting activation energy distributions and the

individual frequency factors are shown in Fig. 7. Here itcan be seen that there is a systematic shift in activationenergy distribution when going from the parameters

evaluated for the oil (C6+) (Emain=55 kcal/mol) to theprimary gas (C1ÿ5 prim.)(E main=57 kcal/mol) and sec-ondary gas (C1ÿ5 sec.) (Emain=60 kcal/mol), while thefrequency factor did not change signi®cantly (9.2 E+15

ÿ6.2E+16 1/min).By using these kinetic parameters, the temperature of

C6+, C1ÿ5 prim. and C1ÿ5 sec. were calculated for a

geological heating rates of 1 K/my. As shown in Fig. 8,the oil generation begins at 80�C (Tmax 140�C). Theonset of gas generation was predicted to take place at

100�C (Tmax 165�C) and is clearly related to the primary

formation of gas from the source rock kerogen.These predictions are in accordance with the kinetic

studies of Braun et al. (1991) and EspitalieÂ et al. (1988)on marine clastic type II source rocks, both coming outwith a temperature range for primary gas generation ina geological interval between 110 and 200 �C. In con-

trast, Pepper and Corvi (1995) predicted the main for-mation of primary gas for much higher temperatures inthe range of 140±210�C. In their study primary gas for-

mation took place parallel to the formation of second-ary gas. However the author pointed out that their gasgeneration kinetics are based on a poor raw data-set

and that they have especially a low con®dence intheir primary gas generation kinetics and resultingpredictions.

The signi®cant generation of secondary gas from thecracking of unexpelled oil in the Duvernay Formationwas predicted to set in at around 150�C (Tmax=180�C),while the end of secondary gas formation is predicted at

250�C. These results con®rm the previous predictions ofDieckmann et al. (1998) and Pepper and Dodd (1995)for Toarcian Shales (type II kerogens), that the oil to

gas cracking processes start earlier in source rocks thanin reservoirs.

4.3. The simulated maturity sequence Ð compositionalpredictions at the molecular level

The MSSV pyrolysis technique allows the generation

of individual compounds in the C1±C30 range to bemeasured. In principle, any or all of these data may bemodelled to predict bulk petroleum compositions in

nature. This section considers the n-alkanes andaromatic hydrocarbons because they make up a highpercentage of natural crude oils in general, and the

unresolved complex mixture (UCM) because it makesup a consistently high proportion of pyrolysis products(Hors®eld, 1997).

The summed yields of n-alkanes in the range C6ÿ14 areshown as a function of pyrolysis temperature in Fig. 9.The displacement of curves to higher temperaturesoccurs with increasing heating rate, as expected, but,

importantly, the maximum yield is heating rate depen-dent, with highest yield occurring for the slowest heatingrate. Yields of compounds contained in the unresolved

Fig. 6. Cumulative formation of C6+, primary gas (C1ÿ5 prim.)

and secondary gas (C1ÿ5 sec.) in mg/g TOC from the immature

sample of the Duvernay Formation (SAP) in the closed MSSV-

pyrolysis at three heating rates (0.1, 0.7 and 5.0 K/min). The

formation curves of C1ÿ5 sec. were calculated from the decrease

of the C6+ formation curves, while the amounts of primary gas

correspond to the di�erence between the total gas (Fig. 5) and

the amounts of C1ÿ5 sec. (Dieckmann et al., 1998).


complex mixture are Ð to a lesser extent Ð also heatingrate dependent, but in this case there is a decrease in themaximum yield as heating rate is lowered.Extrapolated to even slower heating rates, beyond the

practicalities of laboratory measurement into rates thatare typical of sedimentary basins (e.g. 5.3 K/Ma, whichis equivalent to about 1�10ÿ11 K/min), it can be antici-

pated that maximum n-alkane yields would be even higherand UCM yields even lower than suggested by directlaboratory measurements. This phenomenon has also been

reported earlier for n-alkanes and alkylthiophenes in pyr-olysates of the Posidonia Shale (Hors®eld, 1997).``Aromaticity'' is considered in Fig. 10. Shown on the

right-hand side is aromaticity as a function of tempera-ture for di�erent heating rates. In addition to the usualthree heating rates (0.1, 0.7 and 5.0 K/min), note that avery slow experiment was also performed to extend the

database to the limits of what is practicable in labora-tory (0.013 K/min). For any given heating rate, aroma-ticity starts o� high at low temperatures, decreases

during intense n-alkane generation and then increasesagain as n-alkanes are cracked to gas at higher tem-peratures. Absolute aromaticity at the in¯ection point

decreases as heating rate falls. The left-hand side of the®gure presents aromaticity data for naturally occurringvolatile compounds in the Duvernay Formation source

rocks as a function of Tmax. It can be seen that the nat-ural compositional changes with maturity seem to becomparable to the changes in the pyrolysates in thataromaticity ®rst decreases then increases. The minimum

values of natural aromaticity evolution are lower thancorresponding values measured in the MSSV-products.While expulsion e�ects may also have in¯uenced the

natural system (Sandvik et al., 1992) it is consideredbeyond coincidence that the minimum value ®ts with theaforementioned trends extrapolated from the heating

experiments.Minimum values (in¯ection points) of the aromati-

city-trends from the heating experiments and the naturalsource rock bitumen (Fig. 10) have been highlighted and

plotted separately on a semi-logarithmic plot in Fig. 11.The logarithmic scale extends from laboratory heatingrates on the right hand side to geological heating rates

on the left hand side. Furthermore, the numerical value1�10ÿ11 K/min for the geological heating rate is gen-eralised for presentation purposes. The minimum

aromaticities of the natural bitumens, which correspondto the infection area of the natural sample set are shownas a range rather than a single value in Fig. 11 because of

the data scatter at this maturity level, as shown in Fig. 10.A logarithmic regression was applied on the labora-

tory in¯ection points from aromaticity trends shown inFig. 10, in order to extrapolate the heating rate depen-

dent compositional changes in the in¯ection-points tonatural heating conditions of 1�10ÿ11 K/min. Theresults of this prediction purpose are shown in Fig. 11,

Fig. 7. Activation energy distributions (kcal/mol) and fre-

quency factors (1/min) for the formation of C6+, C1ÿ5 tot.,

C1ÿ5 prim. and C1ÿ5 sec. The kinetic calculations are based on

the cumulative formation curves from Figs. 6 and Fig. 5,

respectively.


where the aromaticity values at the in¯ection point ofthe natural trend (from Fig. 10) coincides with the pre-dictions by extrapolated laboratory trend of in¯ection

points (Fig. 11).Heating-rate dependent changes in the aromaticity of

arti®cially generated products have been reported earlierby Stout et al. (1976); Maciel et al. (1979); Fausett and

Mikinis (1981), Campell et al. (1978), Rubel et al. (1983)and Burnham and Singleton (1983). However, it has tobe pointed that high amount of sample material as well

as the generally open system used in these studies didnot allow a clear separation between generation andexpulsion processes. Due to the experimental con®gura-

tion of MSSV-pyrolysis and the extremely smallamounts of sample material envolved during the heatingand GC-online detection of generated products, expul-sion e�ects can be completely excluded here (Hors®eld

et al., 1989). Only the transformation of kerogen tohydrocarbons can be seen to be responsible for theobservation made in Figs. 10 and 11.

Fig. 8. Formation rate (mg per g of kerogen concentrate and per degree) vs. temperature (�C) of liquid hydrocarbons (C6+), total gas

(C1ÿ5 tot.), primary gas (C1ÿ5 prim.) and secondary gas (C1ÿ5 sec.) for the slowest laboratory heating rate of 0.1 K/min and an average

geological heating rate of 1 K/ma.

Fig. 9. Cumulative formation (mg/g TOC) vs. temperature (�C) of the n-C6ÿ14-alkanes and the C6+ unresolved (hump) compounds in

the closed system pyrolysis device (MSSV) at three heating rates (0.1, 0.7 and 5.0 K/min).


Keeping in mind that the H/C ratio of aromatic

structures are lower than the respective ratios in alipha-tic hydrocarbons, the ®ndings from Fig. 11 indicate ahydrogen enrichment of the generated hydrocarbons

with decreasing heating rate. This is in agreement withthe general higher H/C ratio observed in reservoired oilsfrom the Duvernay formation of corresponding matur-

ity (Dieckmann, 1999).A signi®cant heating-rate dependency of maximum yield

can also be seen for the unresolved compound mixture ofarti®cial products. In Fig. 12, this heating rate dependent

trend of the maximum yields of the hump is shownrelative to the corresponding changes of maximumyields of n-alkanes in the C6+ fraction. Hereby, it can

be seen that the relative amount of the unresolved partin MSSV pyrolysis gas chromatograms systematicallydecrease with decreasing heating rate while the max-

imum amounts of n-alkanes increase with lower heatingrates, which leads to a crossover when extrapolatingthese compositional changes to geological heating con-

ditions. Natural crude oils from the Leduc reservoirsprovide a means for con®rming these extrapolations.The oils exhibit a broad span of total n-alkane and totalunresolved components in accordance with a wide

maturity range, the contribution of n-alkanes beinghighest for the most mature crude oils. It is the highestmature oils that are directly comparable with the

experimentally determined n-alkane maximum because

the latter feature is equivalent to a vitrinite re¯ectanceof 1.2% Ro according to Easy Ro predictions (Sweeneyand Burnham, 1990). Interestingly this crossover is

con®rmed.The hydrogen-poor character of arti®cially generated

products with respect to reservoired oils is a well known

phenomenon and was discussed earlier by Hors®eld(1997) by comparing the composition of pyrolysates andnatural oils. Hereby, the arti®cially generated productsare consistently higher in polar and aromatic com-

pounds, while reservoired oils are dominated by hydro-gen-rich compounds (saturates). The systematic increaseof hydrogen enriched compounds with lower heating

rates can be interpreted as an e�ect of the higher avail-ability of free hydrogen during the transformation ofkerogen to hydrocarbons at lower heating rates. Both

the natural and arti®cial formation of hydrocarbons aremainly controlled by free radical formation processes asa result of the thermal cracking of respective precursor

molecules in the source rock kerogen. In nature, wherefree hydrogen is available in large amounts, most of theC bonds cracked during hydrocarbon generation are``healed'' by recombination with hydrogen. This feature

was illustrated by Patience et al. (1992), who balancedquantitatively the number of free radicals and freehydrogen generated under natural conditions. Schenk et

Fig. 10. Comparison between natural and arti®cial compositional changes with ongoing maturity in terms of the ration between

aromates and n-C6-alkanes. On the right-hand side arti®cial changes during MSSV-pyrolysis at four heating rates (0.013, 0.1, 0.7 and

5.0 K/min) are plotted as a function of the pyrolysis temperature. On the left-hand side the compositional changes of the aromates/n-

C6-alkanes ratio in the natural maturity sequence is shown as a function of natural maturity expressed as Rock-Eval Tmax.


al. (1989) illustrated for laboratory heating rates (0.1and 2.0 K/min) that the polycondensation processes

obviously are set in after the main phase of hydrocarbonformation. Because aromatisation and polycondensa-tion processes are thought to be the main source for

hydrogen, these late polycondensation processes underlaboratory conditions might be responsible for thehydrogen de®ciency during the main phase of hydro-carbon formation. The need of free radicals to recom-

bine with each other, if not enough hydrogen isavailable leads to the formation of branched, morecomplex molecules (Lewan, 1994). Probably, these types

of molecules are not resolvable in the gas chromato-graph and are detected as part of the unresovable hump.Van Heek (1982) has reported that the quantity of

free hydrogen increases signi®cantly during laboratorypyrolysis experiments with lower heating rates. Espe-cially he noticed that the amount of hydrogen increases

by 80% when decreasing the heating rate from 35 to 3K/min.Although these experiments were performed on coal

samples, these observation together with the changes of

H/C ratios in the Duvernay pyrolysates underline theimportance of hydrogen availability during closed sys-tem pyrolysis.

Based on the results of the present study, it isobvious that future kinetic studies dealing with the

prediction of natural products must consider theheating-rate dependent changes of hydrocarbon forma-tion.

One possibility could be to develop more complexkinetic models, which consider the heating rate depen-dent compositional di�erences between fast and hightemperature and slow and low temperature heating

conditions. Of course this can be seen as a big challengefor further studies dealing with heating-rate dependentcompositional changes of hydrocarbons generated from

di�erent type of source rocks.An alternative approach was shown in the recent

study. Hereby, the timing predictions were performed

by bulk gas and oil kinetic evaluation, while moredetailed compositional predictions can be performed bythe application of a logarithmic regression as a simpli-

®ed mathematic link between laboratory and naturalcompositional changes. Although this approach wasillustrated only for a restricted maturity window in thepresent work, the novel approach of extrapolating the

laboratory compositional changes with the real naturalcompositional ®ndings clearly illustrate, that the con-cept is valid.

Fig. 11. Aromaticity minimum values (aromatic/n-C6+) from Fig. 10 plotted on a half logarithmic scale as a function of heating rate.

On the left-hand side, aromaticity data from high maturity natural products are plotted. The full line in this diagram illustrates the

prediction of aromaticity using a half logarithmic regression applied on the laboratory data. The natural data are not plotted at the

same geological heating conditions like the laboratory prediction in order to ensure a better overview within the diagram.


5. Conclusions

. For the Duvernay Formation the parallel reactionkinetic model can be applied to bulk hydrocarbonformation and the formation of boiling ranges for

GOR prediction because the total quantities areindependent of the heating rate.

. For a geological heating rate of 1 K/ma the for-mation of oil was predicted to take place between

80 and 160�C (Tmax 140�). Primary gas formation

directly from the Duvernay kerogen was predictedin a temperature interval between 100 and 230�C(Tmax 160

�C).. The cracking of oil to secondary gas in the

Duvernay source rock starts at 150�C and is

completed at 250�C (Tmax 190�).

. On a molecular level, a clear heating-rate depen-dency can be observed leading to the enrichment

of n-alkanes with decreasing heating rate. Becauseof this heating-rate dependency the commonlyused ®rst order parallel reaction model is not sui-table, because single compounds show heating

rate dependency.. This heating-rate dependent compositional chan-

ges of laboratory products could be con®rmed by

natural occurring source rock bitumens and crudeoils.

. A pragmatic way of overcoming this heating-rate

dependency is to make timing predictions usingbulk kinetics, and then infer compositions bysemi-logarithmic extrapolations.

Acknowledgements

This work was carried out as part of V.D.'s PhD at

the Forschungszentrum Juelich (Germany). We wishto thank Anne Richter and Franz Leistner for theirtechnical assistance in the pyrolysis experiments. This

work also has signi®cantly bene®ted from the improve-ments and suggestions by Dr. Chris Clayton and ananonymous reviewer.

References

BeÂ har, F., Vandenbroucke, M., 1996. Experimental determina-

tion of the rate constants of the n-C25 thermal cracking at

120, 400 and 800 bar: implications for high-pressure/high-

temperature prospects. Energy and Fuels 10 (4), 932±940.

Fig. 12. Maximum yields of n-alkanes and the hump at four laboratory heating rates (0.013, 0.1, 0.7 and 5.0 K/min) plotted into a half

logarithmic diagram together with a high mature oil from the Duvernay Formation. The full lines highlight the crossover between the

laboratory trend of the maximum n-alkane and hump-yields as it is con®rmed by the inverse composition of a natural Duvernay oil.


BeÂ har, F., Kressmann, J.L., Rudkiewicz, J.L., Vandenbroucke,

M., 1992. Experimental simulation in a con®ned system and

kinetic modelling of kerogen and oil cracking. Organic Geo-

chemistry 19, 173±189.

BeÂ har, F., Vandenbroucke, M., Teermann, S.C., Hatcher, P.G.,

Leblond, C., Lerat, O., 1995. Experimental simulation of gas

generation from coals and marine kerogen. Chemical Geol-

ogy 126, 247±260.

BeÂ har, F., Vandenbroucke, M., Tang, Y., Marquis, F., EspitalieÂ ,

J., 1997. Thermal cracking of kerogen in open and closed

systems: determination of kinetic parameters and stoichio-

metric coe�cients for oil and gas generation. Organic Geo-

chemistry 26, 321±339.

Braun, R.L., Burnham, A.K., 1990. Mathematic model of oil

generation, degradation and expulsion. Energy and Fuels 1,

153±161.

Braun, R.L., Burnham, A.K., Reynholds, I.G., Clarkson, J.,

1991. Pyrolysis kinetics for lacustrine and marine sources by

programmed micropyrolysis. Energy and Fuels 5, 192±204.

Burnham, A.K., Happe, J.A., 1984. On the mechanics of kero-

gen pyrolysis. Fuel 63, 1353±1356.

Burnham, A.K., Singleton, M.F., 1983. High pressure pyrolysis

of Green River oil shale. In: Miknis, F.P., McKay, J.F.

(Eds.), Geochemistry and Chemistry of Oil Shales. Am.

Chem. Soc. Symposium Series 2, pp. 335±351.

Burnham, A.K., Braun, R.L., Gregg, H.R., 1987. Comparison

of methods for measuring kerogen pyrolysis rates and ®tting

kinetic parameters. Energy and Fuels 1, 452±458.

Burnham, A.K., Schmidt, B.J., Braun, R.L., 1995. A test of the

parallel reaction model using kinetic measurements on

hydrous pyrolysis residue. Organic Geochemistry 23, 931±939.

Campbell, J.H., Koskinas, G.H., Stout, N.D., Coburn, T.T.,

1978. Oil shale retorting: e�ects of particle size and heating

rate on oil evolution and intraparticle oil degradation. In

Situ 2, 1±47.

Carr, A.D., Williamson, J.E., 1990. The relationship between

aromaticity, vitrinite re¯ectance and maceral composition

in coals: Implications for the use of vitrinite re¯ectance as

a maturation parameter. In: Durand, B., BeÂ har, F.

Advances in Organic Geochemistry, Pergamon Oxford, pp.

313±323.

Chow, N., Wendte, J., Stasiuk, L.D., 1995. Productivity versus

preservation controls on two organic-rich carbonate facies in

the Devonian of Alberta: sedimentological and organic pet-

rological evidence. Bull. Ca. Petr. Geol. 43, 433±460.

Cooles, G.P., Mackenzie, A.S., Quigley, T.M., 1986. Calcula-

tion of petroleum masses generated and expelled from source

rocks. In: Leythaeuser, D., RullkoÈ tter, J. (Eds.), Advances in

Organic Geochemistry. Pergamon, Oxford, pp. 235±245.

Creaney, S., Allan, J., 1990. Hydrocarbon generation and

migration in the Western Canada sedimentary Basin. In

Brooks, J. (Ed.), Classical Petroleum Provinces. Geological

Society Special Publication 50, pp. 189±202

Dieckmann, V., 1998. The prediction of oil and gas composi-

tion by the integration of laboratory experiments and case

studies. PhD-RWTH±Aachen. Berichte des For-

schungszentrum Juelich 3648.

Dieckmann, V., Schenk, H.J., Hors®eld, B., Welte, D.H., 1998.

Kinetics of petroleum generation and cracking by pro-

grammed-temperature closed-system pyrolysis of Toarcian

shales. Fuel 77, 23±31.

Dieckmann, V., Schenk, H.J., Hors®eld, B., in press. Asssessing

the overlap of primary and secondary reactions by closed-

versus open-system pyrolysis. Journal of Analytical and

Applied Pyrolysis.

Durand, B., 1980. Kerogen-Insoluble Organic Matter from

Sedimentary Rocks. Editions Technip, Paris.

EspitalieÂ , J., Ungerer, P., Irwin, H., Marquis, F., 1988. Primary

cracking of kerogen. Experimenting and modeling C1, C2ÿ5,C6ÿ15 and C15+ classes of hydrocarbons formed. In: Matta-

velli, L., Novelli, L. (Eds.), Advances in Organic Geochem-

istry. Pergamon, Oxford, pp. 893±899.

Fausett, D.W., Mikinis, F.P., 1981. Simpli®ed kinetics of oil

shale pyrolysis. Colo. School of Mines Press, Golden, CO.

Hors®eld, B., 1997. The bulk composition of ®rst-formed pet-

roleum in source rocks. In: Welte, D.H., Hors®eld, B.,

Baker, D.R. (Eds.), Petroleum and Basin Evolution, Insights

from Petroleum Geochemistry, Geology and Basin Model-

ing. Springer Verlag, Berlin/Heidelberg, pp. 337±402.

Hors®eld, B., RullkoÈ tter, J., 1994. Diagenesis, catagenesis and

metagenesis of organic matter. In: Magoon, L.B., Dow, G.

(Eds.), The Petroleum System from Source to Trap. American

Association of Petroleum Geologists, Tulsa, pp. 189±199.

Hors®eld, B., Disko, U., Leistner, F., 1989. The microscale

simulation of maturation: outline of a new technique and its

potential application. Geol. Rund 78, 361±374.

Hors®eld, B., Schenk, H.J., Mills, N., Welte, D.H., 1992. An

investigation of the in-reservoir conversion of oil to gas: com-

positional and kinetic ®ndings from closed-system programmed

temperatur pyrolysis. Organic Geochemistry 19, 191±204.

Larter, S.R., 1984. Application of Analytical Pyrolysis Techni-

ques to Kerogen Characterisation and Fossil Fuel Exploration/

Exploitation. Analytical Pyrolysis, Methods and Application.

Butterworth, London 212-275.

Lewan, M.D., 1994. Assessing natural oil expulsion from

source rocks by laboratory pyrolysis. In: Magoon, L.B.,

Dow, W.G. (Eds), The Petroleum System Ð from Source to

Trap. AAPG Memoir 60, pp. 201-210

Lewan M.D., Comer, J.B., Hamilton-Smith, T., Hasenmueller,

N.R., Guthrie, J.M., Hatch, J.R. et al., 1995. Feasibility

study of material-balance assessment of petroleum from the

New Albany Shale in the Illinois Basin. US Geol. Surv. Bull.

2137.

Li, M., Yao, H., Fowler, M.G., 1998. Geochemical constraints

on petroleum secondary migration models: revisit the Rim-

bey-Meadowbrook Reef Trend in WCSB. In: Hors®eld et al.

(Eds.), Advances in Organic Geochemistry. Pergamon,

Oxford, pp. 163±182.

Louis, M.C., Tissot, B., 1967. In¯uence de la temperature et de

la pression sur la formation des hydrocarbures dans les

argiles a kerogene. In: Proc. 7th World Petrol. Cong., Vol. 2,

Mexico City, pp. 47±60.

Maciel, G.E., Bartuska, V.J., Mikinis, F.P., 1979. Correlation

between oil yields of oil shales and 13C nuclear magnetic

resonance. Fuel 57, 505±506.

Michels, R., Landais, P., Torkelson, B.E., Philp, R.P., 1995.

E�ects of e�uents and water pressure on oil generation dur-

ing con®ned pyrolysis and high-pressure hydrous pyrolysis.

Geochimica et Cosmochimica Acta 59, 1589±1604.

Muscio, G., Hors®eld, B., 1996. Enhanced formation of inert

carbon during the natural maturation of a marine source rock,

Bakken Shale, Williston Basin. Energy and Fuels 10, 10±16.


Pelet, R., 1985. Evaluation quantitative des produits formes

lors de l'eÂ volution geÂ ochemique de la matieÁ re organique.

Rev. Inst. Fr. PeÂ t. 40, 551±562.

Pepper, A.S., Corvi, P.J., 1995. Simple kinetic models of pet-

roleum formation. Part 1: oil and gas generation from kero-

gen. Marine and Petroleum Geology 12, 291±319.

Pepper, A.S., Dodd, T.A., 1995. Simple kinetic models of pet-

roleum formation. Part II: oil±gas cracking. Marine and

Petroleum Geology 12, 321±340.

Price, L.C., Wenger, L.M., 1992. The control of pressure on

petroleum generation, maturation and thermal destruction as

delineated by hydrous pyrolysis. In: Eckardt, C.D., Maxwell,

J.R., Larter, S.R., Manning, D.A.C. (Eds.), Advances in

Organic Geochemistry. Pergamon, Oxford, pp. 141±160.

Philippi, G.T., 1965. On the depth, time and mechanism of

petroleum generation. Geochimica et Cosmochimica Acta

29, 1021±1049.

Radke, M., Sittard, H.G., Welte, D.H., 1978. Removal of

soluble organic matter from rock samples with a ¯ow-

through extraction cell. Anal. Chem. 50, 663±665.

Radke, M., Willsch, H., Welte, D.H., 1980. Preparative

hydrocarbon group type determination by automated med-

ium pressure liquid chromatography. Anal. Chem. 52, 406±

424.

Rubel, A.M., Margolis, M.J., Haley, J.K., Davis, B.H., 1983.

Bench scale ¯uid retorting of Kentucky oil shale. In: Eastern

Oil Shale Symposium, 13±16 November, pp. 399±405.

Sandvik, E.I., Young, W.A., Curry, D.J., 1992. Expulsion from

hydrocarbon sources: the role of organic absorbtion. Organic

Geochemistry 19 (1±3), 77±87.

Schaefer, R.G., Schenk, H.J., Hardelauf, H., Harms, R., 1990.

Determination of gross kinetic parameters for petroleum

formation from Jurassic source rocks of di�erent maturity

levels by means of laboratory experiments. In: Durand, B.,

BeÂ har, F. (Eds.), Advances in Organic Geochemistry. Perga-

mon, Oxford, pp. 115±120.

Schenk, H.J., Hors®eld, B., 1993. Kinetics of petroleum gen-

eration by programmed-temperature closed- versus open-

system pyrolysis. Geochimica Cosmochimica Acta 57, 623±

630.

Schenk, H.J., Hors®eld, B., 1998. Assessing the reliability of

kinetic timing predictions. In: Hors®eld et al. (Eds.), Advances

in Organic Geochemistry. Pergamon, Oxford, pp. 137±154.

Schenk, H.J., Witte, E.G., Littke, R., Schwochau, K., 1989.

Structural modi®cations of vitrinite and alginite concentrates

during pyrolytic maturation at di�erent heating rates. A

combined infrared, 13C NMR and microscopical study. In:

BeÂ har, F., Durand, B. (Eds.), Advances in Organic Geo-

chemistry. Pergamon, Oxford, pp. 943±950.

Schenk, H.J., Di Primio, R., Hors®eld, B., 1997. The conver-

sion of oil into gas in petroleum reservoirs. Part 1: com-

parative kinetic investigation of gas generation from crude

oils of lacustrine, marine and ¯uviodeltaic origin by pro-

grammed-temperature closed-system pyrolysis. Organic

Geochemistry 26, 467±481.

Stoaks, F.A., Creaney, S., 1984. Sedimentology of a carbonate

source rock: the Duvernay Formation of Alberta, Canada.

In: Longman, M.W., Shanley, K.W. (Eds), Rocky Mountain

Carbonate Reservoirs Ð A Core Workshop. Society of

Economy Paleontologists and Mineralogists, Core Work-

shop No. 7, Golden, CO, pp. 343±375.

Stoaks, F.A., Creaney, S., 1985. Controls on the accumulation

and subsequent maturation and migration-history of a Car-

bonate source rock. In: SEPM Core Workshop Proceedings,

Golden, CO, p. 56.

Stout, N.D., Koskinas, G.J., Raley, J.H., Santor, S.D., Opila,

R.L., Rothman, A.J., 1976. Pyrolysis of oil shale: e�ects of

thermal history on oil yield. Colo. Scho.Mines. Quart. 71, 153.

Sweeney, J.J., Burnham, A.K., 1990. Evaluation of a simple

model of vitrinite re¯ectance based on chemical kinetics. Am.

Ass. Pet. Geol. Bull. 74 (10), 1559±1570.

Tang, Y., BeÂ har, F., 1995. Rate constants of n-alkane genera-

tion from type II-kerogen in open and closed pyrolysis sys-

tems. Energy Fuels 9, 507±512.

Tang, Y., Stau�er, M., 1995. Formation of pristene, pristane

and phytane: kinetic study by laboratory pyrolysis of Mon-

terey source rock. Organic Geochemistry 23, 451±460.

Tissot, B., 1969. PremieÁ re donneÂ es sur les meÂ chanismes et la

cineÂ tique de la formation du peÂ trole dans les seÂ diments.

Simulation d'un scheÂ ma reÂ actionnel sur ordinateur. Rev.

Inst. Fr. PeÂ t. 24, 470±501.

Tissot, B., Califet-Debyser, Y., Deroo, G., Oudin, J.L., 1971.

Origin and evolution of hydrocarbons in early Toarcian

Shales, Paris Basin, France. Bull. Am. Ass. Pet. Geol. 55

(12), 2177±2193.

Ungerer, P., 1990. State of art of research in kinetic modelling

of oil formation and expulsion. In: Durand, B., Behar, F.

(Eds.), Advances in Organic Geochemistry. Pergamon,

Oxford, pp. 1±25.

Ungerer, P., Pelet, R., 1987. Extrapolation of the kinetics of oil

and gas generation from laboratory experiments to sedimen-

tary basins. Nature 327, 52±54.

Van Heek, K.H., 1982. Druckpyrolyse von Steinkohlen. VDI

Forschungsheft, 612, 48.


new heating rate dependency of petroleum-forming reactions: …directory.umm.ac.id/data...

Documents