Comparison between natural and artificial maturations of coals from Mahakam delta, Indonesia

Org. Geochem. Vol. 8, No. 4, pp. 275-292, 1985 Printed in Great Britain. All rights reserved

0146-6380/85 $3.00+0.00 Copyright © 1985PergamonPress Ltd

Comparison between natural and artificial maturation series of humic coals from the Mahakam delta, Indonesia MARC MONTHIOUX~*, PATRICKLANDAIS2 and JEAN-CLAUDE MONIN3 1Centre National de la Recherche Scientifique, 15 Quai Anatole France, 75700 Paris, France 2Centre de Recherches sur la Grologie de l'Uranium, BP 23, 54501 Vandoeuvre les Nancy Cedex, France ~Institut Franqais du Prtrole, BP 311, 92506 Rueil-Malmaison Cedex, France (Received 16 August 1984; accepted 12 February 1985)

A~tract--Type III (humic) organic matter from the Mahakam delta (Indonesia) was chosen to compare artificial and natural coal series. Powdered and concent/'ated immature organic matter was heated in sealed gold tubes for 24 hr at temperatures ranging from 250 to 550°C and under pressures ranging from 0.5 to 4 kb, with and without water. Both elemental and Rock-Eval analyses were used to characterize the products. A comparison between our results, published data and the natural model shows that, quantitatively, natural maturation is simulated better when pyrolysis is performed under confined conditions (no free volume, no diluting inert gas). Thus, pyrolysis in a medium swept by an inert gas, vacuum pyrolysis and some pyrolysis in sealed glass tubes must be considered to be poor simulation tools. The presence of water does not seem to have an essential effect. Allowing the hydrocarbons formed to reach a certain value of partial pressure seems to be important. Results are unchanged when external pressure varies from 0.5 to 4 kb. Key words: humic coals, simulation, maturation, confinement, pressure, water

INTRODUCTION

Laboratory simulation of in situ hydrocarbon formation from kerogen is an important research topic in petroleum geochemistry. Artificial maturation experiments that closely simulate natural diagenesis/catagenesis provide: (l) a better understanding of the mechanisms of petroleum formation and of the role of different natural parameters (temperature, pressure, nature of the mineral phase, pH, water, etc.); (2) data which the observation of natural cases does not give satisfactorily (e.g. nature, amounts and time of gas formation); (3) the data required for creating mathematical models of the formation of oil and gas (Tissot, 1969; Tissot and Espitalir, 1975) and of primary migration (Durand et al., 1983). Defining experimental conditions for the accurate simulation of natural evolution is a difficult problem because of several obstacles. The most important is certainly geological time which is impossible to reproduce in the laboratory. Even though it can be considered (Price, 1982) that time has a minor effect on the evolution of organic matter, most authors feel that the formation of hydrocarbons is a kinetic phenomenon that can be described by an Arrhenius equation, in which time and temperature are inter-

*Present address: Institut Fran~ais du P&role, BP 311, 92506 Rueil-Maison Cedex, France. 275

changeable (Karweil, 1956; Tissot, 1969; Vassoyevich et al., 1970; Lopatin, 1971; Connan, 1974a; Hood et al., 1975; Tissot et al., 1980; Gretener and Curtis, 1982). Nonetheless, laboratory simulations using temperatures much higher than subsurface temperatures in order to compensate for time scales much shorter than geological time are still controversial (Snowdon, 1979). The argument most often put forward is that, at such high temperatures, reactions may be initiated that would not have occurred in nature. Other difficulties arise because of the need to compare the result of artificial evolution with a homologous natural evolution series in order to judge the validity of the simulation. Likewise, such comparisons require a natural series of reference samples from a basin with a constant-nature source material and a long and undisturbed thermal history. Such favorable geological cases are rare. The many thermal maturation experiments performed in different laboratories have used one of three main techniques: (1) pyrolysis in a medium swept by an inert gas (Huck and Patteisky, 1964; Tissot et al., 1974; Durand et al., 1977; Alpern et al., 1978; Huc, 1978; Villey et al., 1979; Solli et al., 1980; Monin et al., 1980; Horsfield and Douglas, 1980; Tissot and Vandenbroucke, 1983); (2) pyrolysis in a sealed tube (usually glass) (Louis and Tissot, 1967; Henderson et al., 1968; Brooks and Smith, 1969; Connan, 1972, 1974b; Ikan et al., 1975; Harwood, 1977; Ishiwatari et al., 1977, 1978, Ishiwatari and Fukushima, 1979; Seifert, 1978; Peters et al., 1980;

276

MARC MONTH1OUXet al.

Mackenzie et al., 1981; Pearson, 1981); (3) pyrolysis in an autoclave (Douglas et al., 1970, 1977; Louis and Tissot, 1967; Bajor et al., 1969; Philip and Russel, 1980; Lewan et al., 1979; Hoering, 1981; Pearson, 1981; Evans, 1983; Winters et al., 1983). Most of these studies are concerned exclusively with the analysis of hydrocarbon effluents. However, there is not much chance that effluents from artificial maturation quantitatively and/or qualitatively resemble effluents from natural maturation if the C, H, O, and N losses from organic matter do not occur at the same time and in the same proportions (as a function of any maturity index whatsoever). These losses are measurable for solid residue, but not for hydrocarbons effluents which thereby do not allow any natural control of oxygen loss, for example. Thus, looking at the chemical behavior of solid residue appears to be an essential first step in judging the validity of a simulation. Even when the behavior of solid residue is examined, the initial samples are often hydrogen rich (organic matter of algal or bacterial origin (Type I) or of marine planktonic origin (Type II)), whereas such organic matter must be considered as poor starting material for testing a simulation method. Indeed, previous publications have stated that, in most cases, as the initial material becomes more oxygen-rich (Type III organic matter, of terrestrial and humic origin) the artificial behavior of solid residue is less and less comparable to natural behavior (Alpern et al., 1978; Villey et al., 1979; Monin et al., 1980). In such a case, the H/C atomic ratios of the solid residues decrease too early, and the O/C atomic ratios stay abnormally high. Getting an accurate simulation from an oxygen-rich material (Type III immature organic matter) would thus be a guarantee of success for simulations performed from other organic matter types, while the contrary is not true. On the other hand, it is important to verify that the simulation effectively reproduces the successive releases of oxygenated compounds (CO2, H20) and hydrogenated compounds (hydrocarbons) which, in nature, characterize evolution from diagenesis through catagenesis (Tissot and Welte, 1978). Furthermore, a comparison between the products of artificial and natural maturations is often not made. When this comparison is made, appreciable differences are found: presence of unsaturated hydrocarbons (Harwood, 1977; Ishiwatari and Fukushima, 1979; Monin et al., 1980; Douglas et al., 1970; Connan, 1974b; Pearson, 1981; Tissot and Vandenbroucke, 1983), absence of or differences in the degree of aromatization of aromatic steroids (Mackenzie, 1980; Mackenzie et al., 1981), differences in the distribution of biomarker isomers such as steranes and hopanes (Huc, 1978; Seifert, 1978), or the absence of such molecules (Pearson, 1981), etc. This article does not pretend to solve all the problems inherent to simulation. It gives an example of an experimental simulation procedure (confined-medium pyrolysis) which provides satis-

factory results for the different aspects examined on the basis of conditions previously mentioned in this section. These results are preliminary ones and, in an initial phase, describe the artificial maturation of organic matter of humic origin (Type III) coming from the Mahakam delta (Indonesia), as observed essentially in solid residue. Comparison with a homologous natural series is emphasized. As presented in a previous paper (Monthioux et al., 1984) the samples were pyrolyzed with a device normally used in mineral geochemistry for hydrothermal syntheses and simulations of metamorphism (Poty et al., 1972; Nguyen Trung et al., 1980; Zimmer, 1983). The effects of temperature, pressure, presence of water, and confinement on the thermal maturation of these coals were studied. The effect of mineral matrix and the characteristics of pyrolytic effluents will be examined and reported upon in a later publication. EXPERIMENTAL AND ANALYTICALTECHNIQUES Selection o f samples

So as to work on sufficiently oxygenated initial material, the samples were of humic origin (Type III) and immature. To avoid possible partial hydrolysis of immature organic material during acid removal of the mineral phase (Durand and Nicaise, 1980), only naturally concentrated organic matter such as lignites and coals were used. Samples were not extracted before the heat treatments. All the samples come from the Mahakam delta (Kalimantan, Indonesia) and are of Mio-Pliocene age. The organic geochemistry of this basin has been studied by Combaz and de Matharel (1978), Verdier et al., (1979), Durand and Oudin (1979), Boudou (1981), Schoell et al. (1983), Vandenbroucke et al. (1983), Hoffman et al. (1984) and Boudou et al. (1984a). The source (equatorial forest) of the organic matter remained relatively constant during deposition, and the geological history was relatively calm. This basin is a good natural model of the thermal maturation of a specific organic matter type as a function of burial. The most evolved coals in these samples reach a stage of maturity corresponding only to R0 ~ 1~ (vitrinite reflectance), which is about in the middle of the main zone of oil formation (middle of catagenesis according to Tissot and Welte, 1978). Thus, samples artificially led to a higher stage of maturity cannot be compared to equivalent natural samples. Elemental and Rock-Eval analyses and depth correlation were used to determine the maturity relationships amongst the samples, which are borehole cuttings. To obtain sufficient quantities of materials for the study, cuttings having similar nature and maturity were combined to obtain the sample mixtures 32362, 32323, 31590 and 31591. Sample number 34454 (well H350S) is not a pure coal but rather a shale very rich in organic matter, as shown by optical microscopic examination (P. Bertrand, IFP). Data from the elemental and Rock-Eval anal-

Comparison between natural and artificial maturation yses of the natural (unextracted) samples are given in Table 1. The organic sulfur contents were very small (< 1%). Experimental procedure About 150 to 200 mg of powdered raw sample was placed in an argon atmosphere inside a thin-walled (0.4mm thick) gold tube 6 m m in diameter and 50mm long with one end of the tube previously welded shut. 50pl (with sample 32362) or 100y1 (with sample 31590) of distilled water (previously deoxygenated by argon bubbling) was eventually added. The empty upper part of the tube not filled by the sample was flattened to diminish the free volume and the amount of argon inside the tube. The second end was welded while the tube was being cooled by liquid nitrogen to prevent evaporation of the water and alteration of the organic matter. The tube was then placed in an autoclave equipped to exert hydrostatic pressure by means of a compressed water-oil mixture (Fig. 1). The apparatus was heated at the rate of 25°C per min to the desired temperature (ranging between 250 and 550°C, _ 5°C). The controlled pressure inside the autoclave was set between 0.5 and 4 kb. The final temperature and pressure was maintained for 24hr. After the isothermal stage, the autoclave was placed in a vertical position, and the tube slide into an area of the autoclave cooled by a constant cold water flow (quench). The tube was then recovered and opened, and its content was analyzed. F o r some experiments, a system allowing the analysis of the noncondensable gases (gaseous hydrocarbons, N2, CO2) by katharometry was used. The solid pyrolysis residue was left for several days in a desiccator before both elemental analysis, in which C, H, O, N and ash were determined separately (performed by Soci6t6 ATX-Nanterre-France) and Rock-Eval analysis (performed according to Espitali6 et al., 1977a,b). This residue was also chloroform extracted and then analyzed. The extract results will be described in a subsequent publication. Also, heat treatments in open-medium pyrolysis (swept by an inert

277

gas) were performed according to a method described elsewhere (Monin et al., 1980). Pressures were chosen within a range (0.5-4 kb) equal to or higher than the pressures encountered in nature. Because of the malleability of gold which guaranteed proper pressure transmission, pressure inside the tube could be considered as quite equivalent to the autoclave pressure. An autoclave pressure greater than 0.5 kb is necessary to prevent bursting of the tubes due to gas formation. The pressure to which the sample inside the tube is subjected is a fluid pressure. Therefore, it is different from the oriented mechanical stress exerted by the weight of sediments. However, the orientation of the pressure is probably important only for the expulsion of fluids during compaction and for the formation of anisotropic carbonaceous residues such as anthracite or graphite. To counter thermal inertia problems and for the sake of convenience, we chose to perform isothermal pyrolyses after a fast ballistic temperature rise. Previous research (Ishiwatari et al., 1977) using pyrolysis at temperatures from 150 to 410°C with times of 5-116hr has shown that, regardless of the temperature, the amount of gas and hydrocarbons produced (fraction soluble in benzene-methanol) increases very quickly during the first 20 hrs, and then much more slowly and asymptotically. Connan (1974b) observed that a maximum of extract is obtained after 24 hr at 300°C. By choosing a period of 24 hr for our experiments, we thought we would reach a zone in which the transformation rate is slow enough so that differences of several minutes in experimental times would not to be significant.

RESULTS

To make an overall check of the agreement of the chemical behaviors of artificial and natural maturation residues, the van Krevelen diagram (van Krevelen, 1961; Durand and Espitali6, 1973; Tissot et

Table 1. Elemental and Rock-Eval analyses of natural samples I

I Corrected

n°

%C

organic

atomic H/C

atomic O/C

atomic NIC

%ash

Free HC t / imgHC/

g.O.C.)

C ;~

HI (mgHC/

Tma x

g.O.C.) Coc)

34454

51.14

65.30

1.035

0.322

0.014

16.6

18

167

410

32362

55.58

63.85

0.931

0.349

0.021

5.9

15

135

418

32323

61.10

70.18

0.916

0.244

0.019

10.5

205

420

31590

75.47

76.92

0,910

0.148

0.023

2.4

279

431

31591

76.20

81.12

0,956

0.098

0.020

5.2

246

446

37252

77.55

81.80

0.930

0.084

285

440

( - ) not determined

15

I I

23

MARC MONTHIOUXet al.

278

OVEN

SEALEDGOLDTUBE 8 SAMPLE / COLDWATER / THERMOCOUPLE FLOW PLEXIGLASS BOX

(

,ETALUCSEAL STEELBOMB

/

,//'

/'n---------;;

VITONSEAL

.../

..,4,,

t ......

COLDWATERFLOW PRESSURE GAUGE

ii / HYDROSTATICPRESSURE ( WATER/OLLMIXTURE)

Fig. 1. Schema of the autoclave.

al., 1974; Tissot and Welte, 1978) is a simple and essential test. Another check having practical significance is the agreement of the variations of petroleum potentials (peak $2 of the Rock-Eval analysis). Data from the elemental and Rock-Eval analyses of the different solid residues after confined-medium pyrolysis are given in Table 2. The influence of a variation in pressure from 0.5 to 4 kb and that of the presence of water are not very obvious. Taking into account the experimental uncertainties (accuracy of temperature regulators and thermocouples, precision of the analyses), the reproducibility of the experiments (when doubles were made) is satisfactory. For these reasons and to make the figures clearer, we have chosen not to represent each of the residues from confined-medium pyrolysis under different conditions (pressure and presence of water) but to give a mean point for each temperature.

artificial evolution paths (after confined-medium pyrolysis) for sample 32362, 34454 and 31590 are plotted using the mean points and are represented by thick dotted lines. A number of patterns are observed: - - A l l the solid pyrolysis residues, for the three initial samples, are situated in the range of existence of humic coals. The parallelism with the average behavior of coals is very good for 32362 and 31590, but not so good for 34454. - - D u r i n g artificial maturation, a sample with a given elemental composition follows its own path. The location of this path in the envelope of humic coals depends on the initial chemical composition. For example, the artificial evolution paths of 32362 and 31590 remain parallel to one another and respect the chemical differences existing in the initial samples. Once again, this is not so true for 34454.

Evolution path of residues Figure 2 shows a van Krevelen diagram (atomic O/C versus atomic H/C) giving the range of existence of humic coals as determined by the analysis of more than 900 raw humic coals (organic C > 40%, data from the Institut Frangais du P6trole) from different origins (envelope of thin dashed lines). The range of existence of Mahakam coals, which is almost as wide, is not represented (Boudou et al., 1984a). This dispersion means that, even though Mahakam coals come from a similar source, the differences in the original chemical composition (leaf, treetrunk, wax, etc.) and/or in the local sedimentation conditions may be great. For example, area B shows the dispersion obtained by an analysis of 16 Mahakam coals (organic C ~ 69%) which have exactly the same degree of evolution since they were taken at depths ranging from 1945.42 m to 1946.64 m from the same core sample (core C3 from well HD1). This dispersion is not due to the poor precision of the elemental analysis since area A, which gives an example of this precision by the dispersion of four analyses of the same sample (32362), is smaller than area B. The

Petroleum potential The corrected organic carbon content (COC = %C x 100/(%C + %H + % 0 + %N)), which will increase with maturation, was chosen as the common maturity index for both artificial and natural evolution series. The Tmaxwas not used because of its imprecision at very low and very high HI values due to difficulties in detection of the $2 peak. Vitrinite reflectance, difficult to measure for a fine powder, was deemed unsuitable. Furthermore, the maximum temperature of the pyrolysis program of the Rock-Eval device was usually set at 550°C, so solid residues with Tmax> 550°C could not be used. Figure 3 shows the variation of HI (in mg of hydrocarbons per g of organic carbon) versus the COC content. The range of humic coals values is again represented, along with the artificial evolution paths, after confined-medium pyrolysis. It can be seen that artificial maturation paths do not agree with the natural evolution of Type III organic matter as well as they do in the van Krevelen diagram (Fig. 2); the HI decreases more rapidly in the simulation than in nature. Artificial

Comparison between natural and artificial maturation maturation patterns, though, reflect the initial differences between the samples, and the HI values for each path pass through a maximum, as they do in the natural system. Production o f oil a n d gas

Figure 4 shows the variation of the freehydrocarbon content as a function of the increasing maturity of solid pyrolysis residues. As a comparison, the shaded strip represents the location of 65 Mahakam samples from three wells (Nilam 25, Kelambu 1 and Handil 627) which are relatively little affected by migration phenomena (Vandenbroucke et al., 1983). The quantities of free hydrocarbons found (expressed in mg per g of organic carbon) were determined by the integration of peak S~ from Rock-Eval analysis and not by an extract weight. These hydrocarbons are in the C5 to C35 range. A number of observations can be made: --The production of hydrocarbons increases than decreases regularly with pyrolysis temperature. The decrease corresponds to the formation of gas. --Whatever the chemical composition (location in the van Krevelen diagram) of the initial coals may be, the quantities of hydrocarbons produced by artificial maturation are of the same order of magnitude. However, a precursor richer in hydrogen (34454) or less oxygen rich (31590) than 32362 produces slightly more hydrocarbons. --Maximum hydrocarbon production with artificial maturation occurs at an organic carbon content of about 85% (pyrolysis temperature = 350-400°C). This seems to be in agreement with the values observed for the Mahakam delta. --The quantities of hydrocarbons released by artificial maturation are of the same order of magnitude as those obtained by natural diagenesis (shaded area). At maximum hydrocarbon production, the natural quantities are systematically less than the artificial quantities. This may be due to the values of the free hydrocarbons in the most immature initial samples (32362 and 34454) which are consistently higher than the values of the natural model (due to the poor accuracy of measurements, or to slight accumulations). - - T h e deepest boreholes in the Mahakam basin provide samples organic matter that has reached the middle of catagenesis. Artificial maturation can go beyond this stage and reach the end of catagenesis and the beginning of metagenesis. The quantitative aspect of simulation by confined-medium pyrolysis thus seems satisfactory. A qualitative study is being made and will be published later on. Encouraging results have already been obtained, and Fig. 5 gives an example. Even though these results must be confirmed by a more systematic study, they are interesting because they give rise to hope that the qualitative agreement may also be satisfactory. Figure 5 represents the distribution of

279

the non-aromatic hydrocarbons (saturates and unsaturates fraction) contained in sample 32362 after artificial maturation by heating to 350°C at 0.5 kb without water (COC = 82.83%) compared to the nonaromatic hydrocarbons contained in natural coal 37252 (well H627), judged to have an equivalent maturity level on the basis of the COC (COC = 81.80%). The distributions of n-alkanes and the pristane/phytane isoprenoids ratios are quite comparable, n-Alkenes are also absent in the artificial maturation sample. Likewise, Table 3 lists the nature of the gases and their quantities in weight percent of initial organic matter obtained after artificial maturation of sample 32362. These analyses were not made systematically, but they nonetheless show that: --The quantities of gaseous hydrocarbons produced during artificial diagenesis (pyrolysis temperature < 300°C) are very slight. In particular, very little methane is produced. ---Carbon dioxide is by far the major constituent of the gases. --The quantities of water and CO2 produced by simulation in gold tubes are in full agreement with the quantities calculated by modeling the diagenetic evolution of the Mahakam basin (Boudou et al., 1984b). DISCUSSION

The behavior of sample 34454 (ash content= 16.6%) is less satisfactory than that of 32362 (ash content=5.9%) and of 31590 (ash content = 2.4%), especially for the chemical balance (Fig. 2). This is quite probably due to its not being a pure coal but made up of an organic matrix very thoroughly mixed with argillaceous minerals. The elemental analyses are thus disturbed by the hydroxyl groups in clays, for example, and in particular the COC is certainly underestimated. This may explain why, for the same heating temperature, the evolution of sample 34454 seems to be "retarded" compared to 32362 and 31590 in Figs 2, 3 and 4. Another possibility is the more direct effect of argillaceous minerals. Monin et al. (1980) showed that a simulation performed on coal mixed with illite resulted in an earlier decrease in the atomic H/C ratio as compared to the same experiment performed on coal alone. The same phenomenon seems to be seen here for 34454 (Fig. 2). Among the studies we have mentioned, the only experiments we can compare to our own are those by Alpern et al. (1978), Villey et al. (1979) and Monin et al. (1980) who used open-medium pyrolysis swept by an inert gas, and Ishiwatari et al. (1977, 1978), Harwood (1977), Peters et aL (1980) and Pearson (1981) who used sealed glass ampules (closed-medium pyrolysis). These authors used sufficiently oxygenated initial material in their simulations and reported the behavior of the solid residue. Figure 6 and Table 4 effectively sum up the behavior of Type III organic matter during open-medium pyrolysis. All the initial coals shown in the figure are

280

MARC MONTHIOUXet al.

Table 2. Elemental and Rock-Eval analyses of solid residues after pyrolysis in gold tubes (confined medium) from samples 32362, 31590 and 34454 11o

Pyrolysis conditions

o~ C

Corrected organic

atomic H/C

atomic O/C

atomic N/C

,=; ash

C ;~

Free HC HI [mg/HC [mg/HC g.O.C.)

g.O.C. I

T ( max °C )

0.SKb

61.84

71.30

0.862

0.233

0.017

8.4

17

125

429

1 Kb

61.88

71.55

0.861

0.231

0.016

10.1

21

134

429

61.81

70.20

0.879

0.249

0.016

7.7

20

166

425

1 Kb

62.31

72.00

0.867

0.223

0.017

10.3

13

122

427

H20

62.90

71.90

0.834

0.227

0.016

7.7

19

152

418

71.39

0.861

0.233

18

140

65.44

76.18

0.834

0.169

0.015

8.9

31

138

439

69.10

77.30

0.811

0.154 ~

0.018

8.2

25

90

440

70.09

77.84

0.793

0.148

0.017

7.9

30

107

440

65.18

76,43

0.821

0,168

0.014

11.1

31

126

439

66.73

78.00

0.798

0.146

0.016

10.9

33

134

442

69.97

77.96

0.793

0.147

0.018

7.2

32

125

439

69.27

77.28

0.803

0.150

0.023

8.0

22

96

435

67.46

77,89

0.845

0.146

0.016

8.3

26

112

439

68.47

77.09

0.812

0.152

0.022

8.4

19

110

440

68.84

77.87

0.792

0.147

0.U18

7.8

17

101

440

69.98

77.92

0.807

0.148

0.018

5.9

19

115

439

77.43

0.810

0.152

26

114

70.61

81.13

0.731

0.116

0.014

12.6

55

55

454

72.97

82.23

0.758

0.097

0.020

8.3

43

78

443

71.86

81.21

0.767

0.107

0.021

7.4

46

89

445

70.19

82.30

0.733

0.104

0.013

11.9

66

84

445

70.33

82.59

0.752

0.099

0.014

11.1

69

82

452

0.5 Kb

H20

m

0.5 Kb

I Kb 0.5 Kb

H20 I Kb H0 2

C'-4 ',4)

3 Kb

C'q pc%

H20

m

0.5 Kb C3 D C~

1 Kb

0.5 Kb H2D

Comparison between natural and artificial maturation

28l

Table 2 (continued) No

Pyrolysis conditions

% C

Free HC Img/HC

HI (rag/He

g o c)

g o c)

12.7

52

92

448

0.017

7.5

63

59

444

0.076

0.019

8.3

0.739

0.090

0.021

9.5

32

34

451

82.68

0.743

0.096

53

64

Correc[ed organic C ;;

atomic H/C

atomic O/C

atomic N/C

% ash

70.51

83.38

0.762

0,088

0.015

74.13

83.89

0.722

0.084

72.71

84.45

0.727

72,60

82.94

max

lec)

1Kb = H20

IKb

72.16

83.58

0.695

0.088

0.019

15.1

60

79

446

3 Kb

71.59

84.09

0.674

0.081

0.022

12.4

52

72

456

83.84

0.685

0.085

56

76

~D m

U

1 Kb

73.94

85.98

0.682

0.064

0.018

Kb

72.86

86.16

0.672

0.063

0,018

86.07

0.677

0,064

86.26

0.576

0,070

=

1

,.--

H0 2 m

0.5 Kb

73.33

63 11.7

58

61 0,015

13.8

49

22

550

I

1 Kb

t'~ 0,4 r~

U

0.5 Kb

c~ o ~

H20 1 Kb

H20

73.05

86.49

0.583

0.069

I 0.014

13.1

57

25

i>550

73.05

88.49

0.570

0.050

0.014

12.8

44

19

550

73.70

87.62

0,609

0.055

0.014

12.8

49

21

>i 550

87.22

0.585

0.061

50

22

m

0.5 Kb

74.88

88.99

0.490

0.048

0.016

10.7

25

9

1 Kb

75.01

87.40

0.526

0.061

0,016

14.0

20

23

73.99

89.54

0.508

0.045

0.012

4.9

37

13

73.36

88.57

0.527

0.054

0.012

14.4

35

12

88.63

0.513

0.052

29

14

0.5 Kb =

H20

c,4 ~

1 Kb

H20

(.J o

o

0.5 Kb

75.45

91.17

0.453

0.032

0.014

14.0

19

3

1 Kb

73.78

90.85

0,480

0.034

0.013

11.6

18

4

0.5 Kb H20

75.15

90.80

0.441

0.038

0.012

12.7

26

7

7a.69

90.52

0.472

0.037

0.014

11.6

27

6

90.84

0.462

0.035

23

5

1 Kb

H20 m

I

/

1

282

MARC MONTHIOUX et al.

Table 2 (continued)

ne

eJ r,'b r~

Pyrolysis conditions

% C

Corrected o/ganic c~

atomic H/C

atomic O/C

atomic N/C

% ash

F/ee HC { mg/HC

g o c)

HI (rag/He

~oc)

T

max

I°c)

~

I l~b

76.03

90.05

0.420

0.043

0.016

16.1

10

3

~

3 Kb

73.99

90.14

0.339

0.048

0.015

16.1

4

4

-

81.12

85.32

0.772

0.063

0.021

3.2

89

118

455

80.73

85.96

0.749

0.057

0.022

3.1

89

109

456

80.88

85.30

0.773

0.062

0.021

3.2

76

89

454

81.66

85.76

0.776

0.056

0.022

2.5

72

134

459

81.90

85.62

0.783

0.057

0.023

2.5

38

103

456

81.03

85.83

0.771

0.055

0.023

2.8

73

67

456

80.84

85.04

0.786

0.062

0.023

2.6

50

141

456

85.55

0.773

0.059

70

109

85.17

88.85

0.619

0.033

0.025

70

30

539

4000C

86.13

89.40

0.655

0.029

0.021

54

33

538

4 Kb

86.79

89.29

0.657

0.028

0.024

49

30

547

=

400°C 0.5 Kb

85.35

87,84

0.644

0.040

0.026

69

27

550

~

H20 87.09

89.33

0.675

0.030

0.019

47

40

533

85.78

88.40

0.681

0.036

0.023

53

35

537

88.85

0.655

0.033

57

33

0.5 Kb

u

4 Kb

o

350QC 0.5 Kb

H20 350oC 4 Kb

CD

N

I'-120 m

4000C 0.5 Mb

u

4000C

1

4 Kb

H20 m N N

1Kb

55.60

72.20

1.042

0.220

0.019

15.8

28

229

418

1Kb

59.01

76.60

0.881

0.162

0.014

13.6

48

197

436

57.66

75.78

0.870

0.174

0.013

19.8

30

187

423

74.86

0.876

0.168

39

192

61.17

80.64

0.838

0.114

0.016

20.7

86

155

448

61.28

81.44

0.817

0.108

0.014

18.8

76

111

449

60.75

81.90

0.770

0.101

0.019

22.1

57

118

454

81.33

0.808

0.108

73

128

o

I Mb

o

H20

& I Kb •-.,n-

u~ -.zl-

U = o

1

Kb

H20 3 Kb

]

Comparison between natural and artificial maturation

Table 2

(continued) PyrolyBPo conditions

n°

r~

283

Corrected organic C ,%

C

atomic

atomic

atomic

H/C

o/c

NIC

~ ash

Free HC

HI

(mg/HC (mg/HC g oc)

g o c)

T

max

(at)

I Kb

62.89

86.22

0.633

0.068

0.014

23.5

70

45

520

1 Kb H20

62.18

86.63

0.691

0.060

0.015

23.9

72

M

465

86./~3

0.662

0.064

71

48

-zr m

(m)

( - ) not determined or not determinable.

._.__._...--- I

mean

values

~

/ I °~I'¢ , , / ~ , ~ " " ~

(~

ENVELOPEOFTYPE~REFERENCECOALS

I

1 oo;

0.3 '

/550

0

0.I

0.2

0.3

04

ATOMICRATIOOIC

Fig. 2. Comparison of natural and artificial evolution paths (pyrolysis in gold tubes) in a van Krevelen diagram.

OIL POTENTIALHI (mg/gORGC) 0

100

I

\ A~

/. ~~

o~

/~ ~~ o

.

\

.I~250

II@,I/N/T/AZSAMPZES

3oo,

3,5_0/

,,~ /

I,~C~.4o;,~o 90"11L~. _.-.---

~'~50-0-0-0 ~ 500

I'''FMEANVALUESI

125o ~f~CF~_A~ \[Lou TEMPERATURE("C; \

\"

I Y///TY/.4I%m9o

I

..-"

I 36s~4_,,-': / ....... 142 4°--t//~/, ...... I'~(~,,~;~o

I.; ~c.~.~.~.

I

HEATTREATMENTTEMPERATUREf°C.)

o'.3

d.4

d.5

ATOMIC RATIO OlC

Fig. 8. Comparison, after extraction of residues, of natural and artificial evolution paths from various studies in a van Krevelen diagram (pyrolysis in gold tubes: Our experiments; pyrolysis in glass tubes: Harwood, 1977; Ishiwatari et al., 1978).

290

MARC MONTHIOUXet al. Table 6. Weight ratios of H20/CO2 quantities produced by different pyrolysis processes on type III organic matter SOURCE: immature organic matter of type III

5OO°C

350aC

350°C

4°C/mn

isotherm 24 h

isotherm 24 h

under vacuum

sealed glass tubes

sealed gold tubes

Pyrolysis conditions

under pressure

Monin et al

Ishiwatari et al

1980

1978

Authors

H20/C0

2.4

1

this paper

< 0.4

by w eig~nt

residue extracts show that artificial maturation may produce results qualitatively similar to those observed in natural systems. To obtain these results, experiments must be performed in a closed and confined system. Confinement conditions must be such that the effluents produced can reach a sufficiently high pressure, although probably not above several tens of bars. G o o d confinement conditions (extremely reduced free volume, no diluting inert gas, etc.) enable the hydrocarbons formed to reach partial pressures high enough for the radical sites (produced by thermal maturation in the residue and in the hydrocarbons) to be deactivated either by recombinations or by hydrogen radicals. F r o m this standpoint, vacuum or open-medium pyrolyses are not good simulation methods. Water as a deactivation agent does not seem to be necessary at this stage since its presence has no effects that can be detected by the techniques used (elemental analysis, R o c k - E v a l analysis). However, experiments were performed only with concentrated relatively hydrogen-poor organic matter. Future investigations should include experiments with more hydrogen-rich organic matter (Type I or II) as well as experiments examining the effects of water and minerals. Acknowledgements--The authors wish to thank Dr B.

Durand (IFP) for helpful discussions and his assistance with the preparation of the manuscript, and Dr B. Poty and C. Nguyen Trung (CREGU) for kindly providing the pyrolysis device facilities. This research was supported by the Institut Franqais du Prtrole (IFP), which also procured for us original samples and analytical techniques.

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