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The Geochemical Characterization of

Sediments from Early Cretaceous SembarFormationA. Nazir

a, T. Fazeelat

a& M. Asif

a

a

Chemistry Department, University of Engineering & Technology,Lahore, Pakistan

Version of record first published: 04 Oct 2012.

To cite this article: A. Nazir, T. Fazeelat & M. Asif (2012): The Geochemical Characterization ofSediments from Early Cretaceous Sembar Formation, Petroleum Science and Technology, 30:23,

2460-2470

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Petroleum Science and Technology, 30:24602470, 2012

Copyright Taylor & Francis Group, LLC

ISSN: 1091-6466 print/1532-2459 online

DOI: 10.1080/10916466.2010.519756

The Geochemical Characterization of Sedimentsfrom Early Cretaceous Sembar Formation

A. NAZIR,1 T. FAZEELAT,1 AND M. ASIF1

1Chemistry Department, University of Engineering & Technology, Lahore,

Pakistan

Abstract The soluble organic matter (SOM) and kerogen of sediments contain

organic molecules, and can be interpreted in terms of source, generative poten-

tial, thermal maturity, and depositional environment of the organic matter. EarlyCretaceous sedimentary sequence of Sembar Formation comprising five sedimentssamples was analyzed. Both SOM and hydrocarbons bound to the kerogen terms as

pyrolyzed organic matter (POM) were characterized geochemically. Hydrous pyrolysiswas carried out to release hydrocarbons from extracted sediments and fractionated

by liquid chromatography. Saturated fractions from both SOM and POM were furtheranalyzed by gas chromatography-flame ionization detector. The study suggested that

Cretaceous sequence of Sembar Formation has fair to good hydrocarbon source poten-tial. Thermal maturity parameters indicate onset of oil genesis zone. The presence of

even carbon numbered n-alkenes, Pr/Ph and Pr/n-C17 versus Ph/n-C18 plots revealmarine algal source and anoxic depositional environment of organic matter from

Sembar Formation.

Keywords early Cretaceous, geochemical characterization, hydrous pyrolysis, kero-gen, Sembar formation

Introduction

Sediments provide a dynamic and long-term reservoir for organic species that include

lipids (solvent-soluble organic matter, including hydrocarbons, fatty acids, and alcohols)

and macromolecular organic matter, all derived from natural biogenic and geologic

sources (Simoneit, 1978). The quantity and quality of organic matter preserved during

diagenesis of sediments ultimately determine the petroleum-generative potential of the

rock. The deposition of organic-rich sediments is favored by a high rate of production oforganic matter and a high preservation potential. Sediments are defined as oxic, dysoxic,

suboxic, and anoxic depending on the oxygen content of the overlying waters. Most

petroleum is generated from source rocks deposited under anoxic to dysoxic environments

because they contain more hydrogen-rich organic matter than do oxic sediments. Anoxic

depositional environments are created from the lack of water circulation below the

photic zone in marine or lacustrine sediments. Anaerobic degradation of organic matter

is thermodynamically less efficient than aerobic degradation (Claypool and Kaplan,

1974). This observation supports the prevailing belief that anoxia is the main cause

for enhanced preservation of hydrogen- and lipid-rich organic matter in petroleum source

Address correspondence to A. Nazir, Chemistry Department, University of Engineering &Technology, Lahore 54890, Pakistan. E-mail: [email protected]

2460


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Geochemical Characterization of Sediments 2461

rocks (Demaison and Moore, 1980). Where oxic conditions exist, the organic matter is

largely destroyed during sedimentation and diagenesis, even when organic productivity

is high. The distribution of alkanes and alkenes in sediments is characterized by distinct

carbon number ranges and has been used for the diagnosis of paleo environments (Pearson

and Obaje, 1999) and organic source input (Cranwell, 1982).

Potential petroleum source rocks are described in terms of the quantity, quality, and

level of thermal maturity of the organic matter. A potential source rock contains adequate

amounts of the proper type of dispersed kerogen to generate significant amounts of

petroleum but is not yet thermally mature. A potential source rock becomes an effective

source rock only at the appropriate levels of thermal maturity (i.e., with the oil-generative

window). The main objective of this work was to evaluate depositional environment,

hydrocarbon-generating potential and thermal maturity of Sembar Formation from the

Lower Indus Basin (Khaskheli-1). This geochemical evaluation will provide information

about the source potential of Sembar Formation that subsequently helps to locate oil and

gas in the area.

Experimental

Geological Description of Sembar Formation

The sediment samples analyzed in this study belong to the Sembar Formation of Creta-

ceous age (well Khaskheli-1). The Khaskheli oilfield is situated in the Badin Block, the

southern central portion of the Lower Indus Basin and is about 31 km in the northwest of

Badin town. The samples were provided by British Petroleum Exploration and Production

Inc. (Islamabad, Pakistan). The Lower Cretaceous Sembar Formation consists mainly of

shale with subordinate amount of siltstone and sandstone. Shale of Lower Cretaceous

Sembar Formation is the main source rock in the Lower Indus Basin and the major

component of oil discovered in Badin Platform is believed to have been sourced from

Sembar shales (Kadri, 1993). Most of the Cretaceous shale contains abundant organic

matter and is deposited over most of the Indus Basin in marine depositional environment

and thickness varies from a few meters to 260 m (Iqbal and Shah, 1980; Kadri, 1993).

Total organic carbon (TOC) values of Sembar in Badin area wells range from 0.5% to

3.5% and average about 1.4% (Wandrey et al., 2004). The Sembar Formation is thermally

mature in the western deeply buried part of the shelf and becomes shallower and less

mature toward the eastern edge of the Indus Basin. Geochemical analyses of rock samples

and produced oil and gas in the Indus Basin have shown that the bulk of the hydrocarbons

produced in the Indus Basin are derived from the Lower Cretaceous Sembar Formation(Wandrey et al., 2004).

Determination of TOC

The TOC was determined by wet combustion titration method (Fazeelat and Yousaf,

2004). Briefly, finally grounded sediment (100 mg) was taken in a dry conical flask and

solution of chromic acid (0.4 N, 10 mL) was added to it. It was placed on a sand bath

for digestion at approximately 175C for 3 min. The contents of the flask were allowed

to cool. The volume was then made up to 100 mL by adding distilled water and five

drops of diphenylamine indicator (0.1 g diphenylamine in 50 mL concentration H2SO4)

were added. The contents of the flask were titrated against ferrous ammonium sulfate

(0.2 N) until endpoint green color was obtained. A blank titration was run parallel to


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2462 A. Nazir et al.

each analysis.

Total Organic Carbon (wt%) D2.16(Blank titer Sample titer)

Blank titer Sample weight

Soxhlet Extraction of Organic Matter

The Soxhlet extractor containing antibumping beads, thimble, and glass wool was pre-

extracted with a mixture of solvents, CH3OH, and CH2Cl2 (1:1, 150 mL) for 24 hr. After

pre-extraction, a known weight of grounded sediment (5 g) was taken in the thimble then

covered with glass wool and placed in the extractor. Solvent mixture (CH3OH:CH2Cl2,

1:1; 150 mL) was taken in the round-bottom flask containing some pre-extracted boiling

chips to ensure smooth boiling and extraction was performed for 72 hr. The soluble

organic matter (SOM) was obtained by careful evaporation of the solvent using rotary

evaporator. The extracted sediments were further used for hydrous pyrolysis.

Hydrous Pyrolysis of Extracted Sediments

Hydrous pyrolysis was performed on extracted sediments (Lewan et al., 1979). The

stainless steel tube reactor was washed with water, alcohol, acetone, and dichloromethane

successively. The extracted sediment sample (500 mg) was taken in the tube reactor

(capacity 25 mL) containing 10 mL triply distilled water. It was purged with nitrogen

(for removal of air and to provide inert atmosphere) and sealed. The tube reactor was

heated at 330C for 72 hr in a furnace. The expelled organic matter from extracted

sediments was obtained after evaporation of water and is called pyrolysate (pyrolyzed

organic matter [POM]). Organic matter thus generated (POM) was subjected to column

chromatography.

Fractionation of SOM and POM by Column Chromatography

Both SOM and POM were fractionated into saturates; aromatics; nitrogen, sulfur, and

oxygen (NSO); and asphaltene and resins fractions by column chromatography on silica

gel. A glass column (40 cm 1.2 cm) was packed with slurry of activated silica gel

(105C, 24 hr, 5 g) in n-hexane (25 mL). The bitumen dissolved in n-hexane (50 l) was

introduced onto the column. The saturated fraction was eluted with three bed volumes

of n-hexane, the aromatics with three bed volumes of 95:5 mixture of n-hexane: diethyl

ether, and NSO with three bed volumes of methanol and asphaltene and resins with threebed volumes of chloroform. The fractions were recovered by careful evaporation of the

solvent on a sand bath followed by the removal of residual solvent under nitrogen. The

fractions were collected in pre-weighed sample vials (Fazeelat and Saleem, 2007).

Gas Chromatography-Flame Ionization Detector Analysis

Sample dilution for gas chromatography was made as follows: 1 mg saturated fraction D

50 L n-hexane, 10 mg saturated fraction D 500 L n-hexane (where 1 mL D 1000 L).

Analysis of saturated fraction was carried using a Shimadzu GC-14B Series (Tokyo,

Japan) gas chromatograph, equipped with a flame ionization detector (FID) and fused

silica capillary column, coated with methyl silicone (OV-1), and 30 m 0.25 mm i.d.

film thickness was 0.25 m. The sample 1 L was injected in splitless mode at 60C.


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Detector (FID) and injector temperatures were 300C and 280C, respectively. The oven

temperature was programmed from 60C to 300C a t 4C/min. Nitrogen at a linear

velocity was used as the carrier gas. The data were collected from retention time 066

min (Fazeelat and Saleem, 2007).

Results and Discussion

A total of five sediments were analyzed and geochemically characterized from the Lower

Indus Basin, Pakistan. Column chromatography and gas chromatography-flame ionization

detector (GC-FID) results from both SOM and POM were used to evaluate depositional

environment, generative potential, and thermal maturity of organic matter of Sembar

Formation.

Depositional Environment

The Pr/Ph ratios, presence of n-alkenes, and saturates/aromatics ratios were used toclassify depositional environment of the sediments.

The Pr/Ph ratio can be used to determine the redox conditions of the sediments

during deposition under the assumption that both pristane and phytane originate from

the same source (e.g., phytol side chain of chlorophyll a). Typically Pr/Ph ratios


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Table1

n-A

lk

anesparametersformaturity,S

OM

,anddepositionalenvironmentofthesedimentsandrelativeabundance(%)ofevencarbonnumbered

n-a

lkenesinthePOM

ofthesediments

SOM

POM

Pr/Ph

Pr/n-C17

Ph/n-C18

Relativeabundance(%)

ofn-alk-1

-enes

Sample

Depth,

m

TOC,

wt%

Bit/

TOC

SOM

,

ppm

POM,

ppm

CPI

OEP

CPI

OE

P

POM

SOM

POM

SOMP

OM

SOM

16

18

20

22

24

A

2,55760

0.7

0.101

900

800

0.92

0.88

0.80

0.8

2

0.68

0.89

0.24

0.17

0.31

0.45

9.68

8.57

9.19

9.41

9.57

B

2,56066

0.8

0.095

1,100

1,200

0.96

0.97

0.89

0.8

8

0.52

0.74

0.23

0.16

0.40

0.36

26.33

30.48

28.23

29.53

29.01

C

2,57985

0.9

0.090

1,300

1,600

0.91

0.80

0.76

0.8

8

0.63

0.89

0.18

0.16

0.37

0.37

25.21

26.78

30.29

26.03

27.48

D

2,58591

0.95

0.092

1,800

1,900

0.95

0.94

0.81

0.8

9

0.51

0.60

0.18

0.15

0.27

0.30

23.51

22.3

22.25

21.96

21.7

E

2,59197

1.00

0.091

2,100

2,700

0.99

0.99

1.06

0.9

1

BDL

0.12

BDL

0.10

BDL

0.28

15.27

11.87

10.04

13.07

12.24

Not

e.CPID

(C21

C

C23

C

C25

C

C27

C

C29)C

(C23

C

C25

C

C27

C

C29

C

C31)/2(C22

C

C24

C

C26

C

C28

C

C30);OEPD

(C21

C

6C23

CC25)/4C22

C

4C24;

relativ

eabundanceofn-alk-1-enesD

peakareaofC16

n-alk-1-ene/peakareaofC16-C24

n-alk-1-enes*100;SOM

D

weightofextract/weightofsedim

entstaken*100;

POM

D

weightofextract/weightofsedim

entstaken*100;16D

C16,n-alk-1-ene;18D

C18,n-alk-1-ene;20D

C20,n-alk-1-ene;22D

C22,n-alk-1

-ene;24D

C24,

n-alk-1-ene.

2464


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Figure 1. Pristane/n-C17 versus phytane/n-C18 (SOM and POM) to infer organic matter and

depositional environment of Sembar Formation sediments (adapted from Connan and Cassou

[1980]). *Isoprenoid/n-alkanes ratios of POM 2591-97 m were below detection limits.

and acids in organic matter, which had been reduced to respective olefins with even

number carbon chain under reducing conditions. The presence of even carbon n-alk-1-

enes with maxima at n-C16 and n-C18 (Figure 3) shows contribution of algal, bacterial,

and fungal organic matter (Alboro, 1976).

Table 2

Column chromatography results of SOM and POM

Relative percentages

Saturates Aromatics NSOs Asphaltenes

Saturates/

Aromatics

Sample POM SOM POM SOM POM SOM POM SOM SOM POM

A 14.00 18.20 34.00 37.45 39.00 29.10 13.00 15.25 0.49 0.41

B 18.64 19.42 31.82 36.00 38.54 31.86 11.00 12.72 0.54 0.59

C 19.60 17.86 29.40 32.14 34.15 32.71 16.85 17.29 0.55 0.67

D 22.50 20.71 27.50 30.71 35.25 32.00 14.75 16.58 0.67 0.82E 21.43 21.66 24.29 28.33 35.43 35.66 18.85 14.35 0.76 0.87


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Figure 2. Gas chromatograms showing distribution of n-alkanes and n-alk-1-enes (*) in saturated

fraction of POM (Samples B and E). Number on peaks refers carbon number of n-alkanes. Pr D

pristane; Ph D phytane; IS D internal standard.

Figure 3. Plot of relative abundance (%) versus carbon number of n-alkenes showing decrease in

concentration ofn-alkenes with both depth and carbon number in POM of sediments. (color figure

available online)


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Figure 4. Classification of sediments (SOM and POM) on ternary diagram (after Tissot and Welte,

1984). Different regions of ternary plot are the following: AA D aromatic asphaltic; AI D aromatic

intermediate; AN D aromatic naphthenic; N D naphthenic; PN D paraffinic naphthenic; P D

paraffinic.

The presence of n-alk-1-enes in sediments is also an indicator of anoxicity of organic

matter (Alboro, 1976) that supported earlier findings about the depositional conditions

(see previous). Table 2 suggests organic matter type from the relative amount of weight

percent of compound classes supported by the ternary plot. The position of the samples of

the well Khaskheli-1, on ternary plot (Figure 4) for bitumen and POM show that on going

from 2,557 to 2,597 m the bitumen composition changes from aromatic naphthenic to

paraffinic naphthenic. It shows a gradual increase in paraffinic and naphthenic character

with an increase in depth. The plot also suggests that the organic matter type is marine.

Generative Potential of Sediments from Sembar Formation

Generative potential is the total amount of organic matter present as solvent soluble

hydrocarbons and kerogen (i.e., SOM and POM). The amount of SOM illustrates thefraction of generative potential that has been effectively transformed into hydrocarbons,

while the amount of POM indicates remaining hydrocarbon potential yet to generate

hydrocarbons in sediments. Generative potential of the Sembar Formation sediments is

determined by measuring TOC, SOM, and POM.

The primary prerequisites for a potential source rock are the quantity, quality, and

thermal maturity of organic matter it contained. TOC values of the analyzed sediments

lie in the range of 0.71.0 wt% (Table 1). Peters and Cassa (1980) suggested TOC values

as poor (TOC 2 wt%). The TOC results from Sembar Formation sediments indicate that most

of them have good source rock potential.

The quantity of organic matter in sediments is interpreted in terms of extracted

(SOM) and bound hydrocarbons (POM). Detailed compositional analysis of SOM in


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conjunction with kerogen yields the necessary information to make at least semiquanti-

tative predictions about the amount of petroleum, which have been or will be generated

by a given amount of source rock. Generally, the samples containing value of SOM

less than 300 ppm are not considered for source rock potential evaluation (Wasim et al.,

2004). The values of SOM for the analyzed samples range from 900 to 2,100 ppm, which

shows good potential. The values of POM for the analyzed samples range from 800 to

2,700 ppm (Table 1), which is also consistent with SOM and indicates good source rock

potential (Peters and Cassa, 1994).

Thermal Maturity of Sediments From Sembar Formation

Thermal maturity of the samples was determined by bitumen transformation ratio (Bit/

TOC), carbon preference index (CPI), odd-even predominance (OEP), saturates/aromatics

ratio, and isoprenoids to n-alkane ratios. The ratio of extractable bitumen to TOC, called

the transformation ratio, ranges from near zero in shallow sediments to 0.25 (i.e., upto 250 mg/g of TOC) at peak oil generation (Peters and Cassa, 1994). Bit/TOC ratio

is shown in Table 1, where the values (0.090.10) indicate thermal maturity of Sembar

Formation sediments lay within the oil window (cf. Peters and Cassa, 1994). CPI and

OEP are influenced by degree of maturation and type of organic matter. CPI and OEP

values are calculated by using the formula given by Bray and Evan (1961) and Scalan

and Smith (1970).

The CPI are calculated from n-alkanes in the range of C21-C31 carbon numbers and

OEP in the range of C21-C25 carbon numbers (Scalan and Smith, 1970); however, the

range can be adjusted to include any specified range of carbon numbers. The OEP values

increase from 0.80 to 0.99 for SOM and 0.82 to 0.91 for POM as they move from top to

the bottom of the sample sequence. Similarly, CPI values changes from 0.91 to 0.99 for

SOM and 0.76 to 1.06 for POM as the move down to depth of the sediments samples.

This increase in CPI and OEP values reveals thermal maturity of Sembar Formation

sediments increases with increase in depth. The OEP and CPI significantly above or

below 1 indicate thermally immature oil or extract, whereas value of 1 indicates higher

thermal maturity (Peters et al., 2005).

The hydrocarbon composition of sediments was determined using capillary gas

chromatography and Figure 4 shows the GC-FID chromatograms of the representative

sample. Similarly each sediment sample saturated fraction exhibits unimodel n-alkanes

distribution with slight even predominance in the carbon range of C20-C30. SOM was

fractionated into saturates, aromatics, NSOs, and asphaltenes components using col-umn chromatography on silica gel (Table 2). The column chromatographic analysis

of SOM and POM reveals high proportion of aromatic hydrocarbons and polars than

saturated hydrocarbons. The saturate/aromatic ratio observed for the samples increases

with depth from 0.49 to 0.76 for SOM and 0.41 to 0.87 for POM. It is suggested that

saturates/aromatics ratio increases with maturity that indicate maturity of the samples is

increasing with depth (Peters et al., 2005).

The Pr/n-C17 and Ph/n-C18 ratios decrease with increasing thermal maturity as more

n-paraffins are generated from kerogen by thermal cracking (Tissot et al., 1971). The

ratios can be used to evaluate the thermal maturity of nonbiodegraded oils and bitumens

(Peters et al., 2005). The Pr/n-C17 and Ph/n-C18 ratios for the samples are shown in

Table 1 and values are in the range of 0.180.24 and 0.270.40 for POM and 0.10

0.17 and 0.280.45 for SOM, respectively (Table 2). The isoprenoids to n-alkanes ratios


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decrease with depth, which indicates a rise in thermal maturity with increasing depth of

Sembar Formation (Table 1).

Conclusions

Pr/Ph ratio indicates anoxic depositional environment of sediments. Position of SOM and

POM on ternary diagram shows reducing depositional conditions and marine source of

organic matter. Presence of even carbon n-alkenes indicates anoxicity and low maturity

of sediments, particularly in the upper part of the sedimentary column as compared

with deeper samples and also probably show marine anoxic depositional environment.

Pr/Ph and Pr/n-C17 versus Ph/n-C18 plots indicate source of organic matter is marine

algal, deposited under reducing sedimentary environment and increasing maturity with

depth. SOM, POM, and TOC reveal good source rock potential for the Sembar Formation

sediments. Thermal maturity indicated by Bit/TOC ratio reveals that the organic matter

of sediments is within the oil window. CPI and OEP values show increasing thermal

maturity with increasing depth.

References

Alboro, P. W. (1976). Bacterial waxes. In: Chemistry and Biochemistry of Natural Waxes, Kol-

latukudy, P. E. (Ed.). New York: Elsevier, pp. 419445.

Bray E. E., and Evan, E. D. (1961). Distribution of n-paraffins as a clue to recognition of source

beds. Geochim. Cosmochim. Acta 22:215.

Claypool, G. E., and Kaplan, I. R. (1974). The origin and distribution of methane in marine

sediments. In: Natural Gases in Marine Sediments, Kaplan, I. R. (Ed.). New York: Plenum

Press, pp. 99140.

Connan, J., and Cassou, A. M. (1980). Properties of gases and petroleum liquids derived fromterrestrial kerogen at various maturation levels. Geochim. Cosmochim. Acta 44:123.

Cranewell, P. A. (1982). Lipids of aquatic sediments and sedimenting particulates. Prog. Lip. Res.

21:271308.

Demaison, G. J., and Moore, G. T. (1980). Anoxic environments and oil source bed genesis. AAPG

Bull. 64:11791209.

Derenne, S., Largeau, C., Hetnyi, M., Brukner-Wein, A., Connan, J., and Lugardon, B. (1997).

Chemical structure of the organic matter in a Pliocene maar-type shale: Implicated Botryococ-

cus race strains and formation pathways. Geochim. Cosmochim. Acta 61:18791889.

Fazeelat, T., and Yousaf, M. S. (2004). Geochemical characterization of outcrop sediments from

Dharangi upper Indus Basin-Pakistan. J. Chem. Soc. Pak. 26:355359.

Fazeelat, T., and Saleem, A. (2007). GC-FID analysis of wax paraffins from Khaskheli crude oil.

J. Chem. Soc. Pak. 29:492499.Iqbal, M. W. A., and Shah, S. M. I. (1980). A Guide to a Stratigraphy of Pakistan: Geological

Survey of Pakistan Records. Quetta, Pakistan: Geological Survey of Pakistan.

Kadri, I. B. (1993). Cretaceous Source Rocks in Pakistan. AAPG/SVG International Conference

and Exhibition, Caracas, Venezuela, March 1417.

Lewan, M. D., Winters, J. C., and McDonald, J. H. (1979). Generation of oil-like pyrolyzates from

organic-rich shales. Science 203:892899.

Lijmbach, G. W. M. (1975). On the origin of petroleum. Proc. 9th World Pet. Conf. 2:357369.

Pearson, M. J., and Obaje, N. G. (1999). Onocerane and other triterpenoids in Late Cretaceous sedi-

ments from the Upper Benue Trough, Nigeria: Tectonic and palaeoenvironmental implications.

Org. Geochem. 30:583592.

Peters, K. E., and Cassa, M. R. (1994). Applied source rock geochemistry. In: The PetroleumSystemFrom Source to Trap. Magoon, L. B. and Dow, W. G. (Eds.), Tulsa, OK: AAPG,

Tulsa, pp. 93117.


12/12


Peters, K. E., Walters, C. C., and Moldowan, J. M. (2005). The Biomarker Guide, 2nd Ed.

Cambridge, England: Cambridge University Press.

Scalan, K. S., and Smith, J. E. (1970). An improved measure of odd-even predominance in the

normal alkanes of sediment extracts and petroleum. Geochim. Cosmochim. Acta 34:611620.

Seifert, W. K. (1978). Geochim. Cosmochim. Acta 42:473484.

Simoneit, B. R. T. (1978). The organic chemistry of marine sediments. In: Chemical Oceanography,Vol. 7, 2nd Ed., Riley, J. P., and Chester, R. (Eds.). New York: Academic Press, pp. 233311.

Tissot, B., Califet-Debyser, Y., Deroo, G., and Oudin, J. L. (1971). Origin and evolution of

hydrocarbons in early Toarcian shales, Paris Basin, France. AAPG Bull. 55:21772193.

Tissot, B. P., and Welte, D. H. (1984). Petroleum formation and occurrence. 59:236.

Wandrey, C. J., Law, B. E., and Shah, H. A. (2004). Sembar Goru/Ghazij Composite Total Petroleum

System, Indus and Sulaiman-Kirthar Geologic Provinces, Pakistan and India. U.S. Geol. Surv.

Bull. 2208:13.

Wasim, A., Shahnaz, A., and Samina, J. (2004). Techniques and Methods of Organic geochemistry

as Applied to Petroleum Exploration. Pak. J. Hydrocarb. Res. 14:6977.

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