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An improved understanding of the alteration of molecular compositions by severe to extreme biodegradation – a case study from the Carboniferous oils in the eastern Chepaizi Uplift, Junggar Basin, NW China Xiangchun Chang, Honggang Zhao, Wenxiang He, Xu Yaohui, Youde Xu, and Yue Wang Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b01557 • Publication Date (Web): 21 Jun 2018 Downloaded from http://pubs.acs.org on June 22, 2018

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An improved understanding of the alteration of molecular compositions by severe to extreme biodegradation – a case study from the Carboniferous oils in the eastern Chepaizi Uplift, Junggar Basin, NW China Chang Xiangchun*,a,b, Zhao Honggang a, He Wenxiangc, Xu Yaohuic, Xu Youded, Wang Yuea a

College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao

266590, People’s Republic of China b

Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and

Technology, Qingdao 266071, People’s Republic of China c

College of Resources and Environment, Yangtze University, Wuhan 430100, People’s Republic of China

d

Research Institute of Petroleum Exploration and Development, Shengli Oil Company, Sinopec, Dongying,

257001, People’s Republic of China ABSTRACT: Biodegraded oils have been widely discovered throughout the world, whereas the alteration of the molecular composition of oils at extreme levels (>PM8) has been insufficiently documented. A suite of crude oils from Carboniferous volcanic reservoirs in the eastern Chepaizi Uplift, Junggar Basin, experienced severe to extreme biodegradation (PM6+ to PM9+), which provided an ideal case for the present study. This investigation showed that the variations in molecular composition were not strictly consistent with their stepwise fashion in established schemes. The idea that the 25-norhopanes are derived from hopanes was confirmed by the sharp decreases in the C29 hopane/gammacerane (C29H/G) and C30 hopane/gammacerane (C30H/G) values at the level of extreme biodegradation, which were associated with the increases in their counterparts of C28 25-norhopane/gammacerane (C28 25-NH/G) and C29 25-norhopane/gammacerane (C29 25-NH/G). 25-norhopanes were also biodegraded at an extreme level, with C29 25-NH being more susceptible than C28 25-NH. The preferential biodegradation of individual homohopanes by carbon number occurred at an extreme level, whereas C29H featured more bio-resistance than C30H and shared a similar susceptibility to biodegradation as 18α-30-norneohopane (C29Ts). The formation of 22R isomers for 25- norhopanes seemed to be favored over that of 22S isomers, although the 22S isomer was degraded faster that the 22R epimer for the C31, C32 and C33 homohopanes. However, the constant values of 22S/(22S+22R) for the C34 homohopane implied no preferential biodegradation of 22S or 22R isomers for this extended hopane. Lower- molecular- weight tricyclic terpanes (TT) were

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preferentially removed at extreme biodegradation levels, and the late-eluting stereoisomers were degraded faster than the early-eluting ones for C26TT, C28TT and C29TT. C24 tetracyclic terpane (C24Tet) is much more resistant to biodegradation than TTs. Pregnanes have a similar susceptibility to biodegradation as gammacerane, but they are more resistant than C23TT. The biodegradation of regular steranes was characterized by their faster depletion than diasteranes and the preferential depletion of C27 regular sterane to the C29 homolog and the 20R isomers to the 20S isomers. At the extreme level, even C20 and C21 triaromatic steroids (TAS) were distinctively reduced, coexisting with the relatively highly degraded steranes and terpanes, although water washing can also be responsible for the decreases in (C20+C21)TAS/C26-28-TAS values. Keywords: extreme biodegradation; biomarker; sequential degradation; 25-norhopane; Chepaizi Uplift 1. INTRODUCTION Assessing the molecular oil composition, combined with other techniques and processes, plays a significant role in supporting oil exploration and production.1 Well-documented oil compositions are crucial. However, most of the world’s petroleum is biodegraded,2 and even exceeds the amount of conventional oil worldwide, profoundly affecting the petroleum hydrocarbon composition and quality of crude oil.3–5 Biodegraded oil typically shows increases in sulfur content, oil acidity, oil viscosity and certain metal contents, a decrease in API gravity, and enrichment in NSO-bearing compounds.

6–12

Various schemes have been proposed to

assess the extent of biodegradation based on the presence or absence of key compound classes,13, 14 or nine-point scales, according to the extent to which the distribution of saturated hydrocarbons had been altered by biodegradation.15 This was later expanded to include aromatic hydrocarbons,16 or ten-point scales (usually called PM1–10);17 more comprehensive compound classes;18 Manco scales, which are based on integrating the extent of biodegradation of various aromatic compounds and steranes;19 post-extreme plus levels 1–4 of biodegradation differentiated on the basis of the presence and absence of ‘refractory’ components, together with 25-norhopanes (25-NH), 17-nortricyclic terpanes and C23 demethylated tetracyclic terpane.20 However, steranes, diasteranes and hopanes can be degraded during the formation of 25-norhopanes.21 Furthermore, oil samples can display orders of magnitude of variation in their viscosity values at the same level of biodegradation.19 An investigation of a downhole profile in the Bohai Bay Basin indicated that sequential microbial degradation of hydrocarbons under anoxic conditions does not occur in a true stepwise fashion, but is controlled by the concentration and solubility of hydrocarbons and their


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diffusion rate to oil/water contact.22 The poor definitions of the rates, pathways and environmental factors that influence subsurface biodegradation, may be responsible for the inconsistent behavior of the biodegradation scales.23 Furthermore, the influence and susceptibility between pregnanes, tri- and tetracyclic terpanes and non-hopane pentacyclic terpanes at extreme biodegradation levels (>PM8) may also need to be understood in depth.20 Here, we report a biomarker analysis of a suite of crude oils from the Chepaizi Uplift, which is located in the northwestern margin of the Junngar Basin, in an attempt to assess the molecular changes in oils at severe to extreme levels of biodegradation. The investigated Carboniferous oils exhibited a sequential rank of biodegradation (from severe to extreme), which offers an ideal case for investigation. 2. GEOLOGICAL SETTING AND SAMPLES 2.1. Geological Setting. The Chepaizi Uplift, an inherited paleohigh that formed in the early stage of the late Hercynian tectonic movement,23 is located in the western margin of the petroliferous Junggar Basin, NW China (Fig. 1), and it covers an area of approximately 10,500 km2. It is bounded by the Zhayier Mountains to the northwest, the Sikeshu Sag to the south, and the Hongche Fault to the east (Fig. 1). The Chepaizi Uplift has undergone a series of evolution stages, including strong uplift in the late Carboniferous to Jurassic; slow subsidence in the Cretaceous to Neogene; and rapid subsidence in the Neogene to the Quaternary.24–26 Since the 1960s, commercial volumes of oil have been obtained from Cretaceous, Jurassic, Palaeogene and Neogene clastic reservoirs in the Chepaizi Uplift. The 21st century witnessed a breakthrough in the petroleum exploration in Carboniferous volcanic rocks.

27, 28

The fluids occurring in

Carboniferous intervals are mainly heavy oils that have been altered by biodegradation at different levels. The two surrounding generative source kitchens (the Changji Sag to the east and the Sikeshu Sag to the south) were the main hydrocarbon contributors in this study. However, the Carboniferous heavy oils in the eastern and western areas of the Chepaizi Uplift were mainly derived from the Permian source interval (P2w) in the Changji Sag and the Jurassic source interval in the Sikeshu Sag, respectively. Basalt, andesite, tuff and volcanic breccia served as reservoir rocks, which experienced multi-stage secondary reconstruction (weathering, leaching, dissolution and fracturing processes) and improved the reservoir qualities of the Carboniferous volcanic rocks.28 Well-developed faults were interconnected with unconformities and carriers and affected the migration orientations and pathways, thus constraining the distribution of petroleum there.


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2.2. Analytical Methods. Nine crude oils of Carboniferous reservoirs were collected from all the nine production wells in the eastern Chepaizi Uplift, which were severely biodegraded. After extracting de-asphaltene with an excess of hexane, the crude oils were fractionated into saturated, aromatic and resin fractions with column chromatography (silica gel/alumina, 3:1), eluting with n-hexane, a mixture of CH2Cl2 and n-hexane (7:3, v: v), and a mixture of CHCl3 and CH3OH (1:1, v: v), respectively. The saturated and aromatic hydrocarbons were further analyzed using gas chromatography–mass spectrometry (GC–MS) with an Agilent 6890 gas chromatograph coupled to an Agilent 5975i mass spectrometer. A HP-5MS column (60 m×0.25 mm i.d. ×0.25 µm film thickness) was used, with the oven temperature programmed to increase from 50 °C (held 1 min) to 120 °C at 20 °C /min, to 310 °C (held 25min) at 3 °C /min. He carrier gas was maintained at a constant 1 ml/min, and the temperature of the injector was 300 °C. The mass spectrometer was operated in full scan mode or selected ion monitoring (SCAN/SIM) mode, with an ionization energy of 70 eV. D-C24 was added to the saturated fraction as an internal standard before GC– MS analysis. The peak area was used for calculation of concentrations and molecular parameters. 3. RESULTS AND DISCUSSION 3.1. Source of Investigated Oils. The Sikeshu Sag and the Changji Sag, two hydrocarbon-generating sources, are responsible for the petroleum discovered around the Chepaizi area.29–35 Oils derived from the Jurassic Badaowan Formation (J1b), which were deposited in fairly fresh lacustrine environments, are characterized by high pristane/phytane (Pr/Ph) ratio values (>2.00), low gammacerane/C30 hopane (G/C30H, -27‰). The dark shales of the Lower Permian Fengcheng Formation (P1f) and mudstones of the Middle Permian Wuerhe (P2w) were indicative of relatively fresh-water and saline water lacustrine environments, respectively.29, 30, 34 The P1f-sourced oils showed low Pr/Ph ( αββ20R > αββ20S > ααα20S and C27 > C28 > C29.13,

43, 61

Diasteranes are particularly resistant to biodegradation, as evidenced by the complete

destruction of C27-C29 regular steranes before the alteration of diasteranes.

36, 55

Comparatively, pregnane

and homopregnane are more resistant to biodegradation than both regular steranes and diasteranes, 13, 43, 44, 50, 60, 62, 63

and were usually used as internal markers to assess the mass of oil removed during heavy to

severe biodegradation.50 For the investigated Carboniferous oils at severe to extreme extent of biodegradation, an almost linear correlation with gammacerane concentrations suggested that pregnanes have a susceptibility to biodegradation similar to that of gammacerane (Fig. 6a). Pregnanes remained in high concentrations when the C23TT content approached zero, indicating that C23TT was more vulnerable to biodegradation than pregnanes at extreme levels of alteration (Fig. 6b). The negative correlations of (αα+ααββ) 20S/(αα+ααββ) 20R and 20S/(20S+20R) for C29 sterane with the concentration of gammacerane suggested that the 20R isomers are preferentially removed by microbial degradation over the 20S isomers (Figs. 6c–6d). The biodegradation of regular steranes seems to be faster than that of the diasteranes, as evidenced by the increase in the C27-diasteranes/C27-regular steranes ratios (C27DS/C27RS) from 0.06 to 0.52 when the concentrations of diasteranes decrease from 120 µg/g to 27.6 µg/g (Fig. 6e). The concentrations of diasteranes decreased as the biodegradation level increased, the ratio ααα(20R)C27 sterane/C29 sterane first increased and then decreased with the biodegradation level of PM8 as the turning point (Fig. 6f), suggesting the preferential degradation of the C27 regular sterane to the C29 homolog. 3.2.4. Triaromatic Steroids. Aromatized steroids appear to be mostly resistant to biodegradation and remain unaltered at all but the biodegradation level of PM 10.7 There are only a few cases where altered aromatized steroidal hydrocarbons were recorded.16, 44, 59, 64, 75 In theory, once the short-chained aromatic steroids are altered, all steranes and terpanes should be completely depleted.13, 15, 17 However, for the investigated oils, this regularity does not hold true. With the increase in biodegradation level from group A to group D, the Carboniferous oil showed an evident reduction of C20 and C21 triaromatic steroids (TAS) and highly degraded steranes and terpanes (Fig. 2). From group A to group D, the ratios of


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(C20+C21)-TAS/C26-28-TAS and TA(I)/(I+II) decreased sharply from 0.17 to 0.03, and from 0.14 to 0.03, respectively, whereas the C26/C28(20S)-TAS and C27/C28(20R)-TAS ratios remained at approximately 0.12– 0.15 and 0.72–0.79 (Figs. 7a–7b), respectively, implying that the short-chained TAS are slightly more susceptible to biodegradation than the long-chained counterparts. Although water washing or biodegradation can be responsible for the variations in (C20+C21)-TAS/C26-28-TAS,7 the obvious decreases in (C20+C21)-TAS/C26-28-TAS (0.17 to 0.11) and TA(I)/(I+II) (0.14 to 0.10) in group A certainly confirmed the effect of water washing in addition to that of biodegradation (Table 1). 4 CONCLUSIONS Carboniferous oil from the eastern Chepaizi Uplift of Junggar Basin was biodegraded at severe to extreme levels (PM6+ to PM9+), where the attacks of tricyclic terpanes, diasteranes and short-chained triaromatic steroids were observed in addition to the alteration of molecular compositions relatively susceptible to biodegradation. The sequential microbial degradation of hydrocarbons did not appear to be strictly consistent with the stepwise fashion in established schemes. The investigation supported the hypothesis that the 25-norhopanes were derived from hopanes. Non hopanoid biomarkers, i.e., gammacerane, C30 diahopane, C24 tetracyclic terpane and pregnanes are highly bioresistant and can be used as internal standards for semi-quantitative evaluation at extreme biodegradation levels. The sequential biodegradation of hopanes and steranes occurred at extreme levels, as did the preferential depletion

of

higher-molecular-weight

homohopanes

and

25-norhopanes,

faster

reduction

of

lower-molecular-weight regular steranes, greater susceptibility of 22S epimers for C31, C32 and C33 homohopanes than 22R epimers, and faster degradation of regular steranes than diasteranes, which were consistent with the existing proposals. However, the lack of the preferential biodegradation of 22S to 22R epimers for C34 homohopane, the alternate preference of 22S and 22R for C35 homohopane, and the preferential removal of the 20R isomers to the 20S isomers for C29 regular steranes implied a different and complex biodegradation mechanism at the extreme level. Meanwhile, the highly bioresistant TTs were altered at extreme biodegradation levels, and in addition to the preferential reduction of lower-molecular-weight TTs, the depletions of late-eluting stereoisomers for C26TT, C28TT and C29TT were faster than those for early- eluted stereoisomers. AUTHOR INFORMATION Corresponding Author


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*Telephone: +86-532-80691766. E-mail: [email protected]. ORCID

Xiangchun Chang: 0000-0002-2499-9045 Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS This study was co-funded by the National Natural Science Foundation of China (Grant No. 41772120), Shandong Province Natural Science Fund for Distinguished Young Scholars (Grant No. JQ201311). Sinopec Shengli Oil Company was thanked for the providing samples and approve of publication. Dr. Ryan P. Rodgers and two anonymous reviewers were greatly acknowledged for their critical comments and constructive suggestions. References [1]

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1619–1634. Tables and figures caption Table Table 1. Bulk compositions and molecular parameters of Carboniferous rude oils from Chepaizi Uplift. NSO: resin + asphaltene; TT: tricyclic terpane; Tet: tetracyclic terpane; G: gammacerane; H: hopane; NH: 25-norhopane; C30D: C30 17α(H) diahopane; C29Ts: C29 18α(H)-30-norneohopane; E/L: early eluted/late eluted tricyclic terpane; C27/C29RS: ααα(20R)C27 regular sterane/ααα(20R)C29 regular sterane; 20S/(20S+20R): C29 sterane ααα20S/(ααα20S+ααα20R); C27DS/C27RS: C29 diasterane/C27 regular sterane;


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(C20+C21)/C26-28: (C20 triaromatic steroid + C21 triaromatic steroid)/C26-28 triaromatic steroids; C26/C28S: C26 triaromatic steroid(20S)/C28 triaromatic steroid(20S); C27/C28R: C27 triaromatic steroid(20R)/C28 triaromatic steroid(20R); (αα+αββ)20S/20R: C29 sterane (ααα20S+αββ20S)/ C29 sterane (ααα20R+αββ20R); DS: diasteranes; ∑PTs: summed concentrations of pentacyclic terpanes; ∑TTs: summed concentrations of tricyclic terpanes.

Figures Figure 1. Map showing structural units of the Junggar Basin (a), with locations of the Chepaizi Uplift and nearby discovered oilfields (b), and field-scale map showing the positions of production wells and faults in the eastern Chepaizi Uplift (c).

Figure 2. Representative saturated and aromatic fractions fragmentograms of Carboniferous oils with different biodegradation levels showing molecular compositions. (a) m/z 191: C19~C24, C26 and C28: tricyclic

terpanes

with

different

carbon

numbers;

Ts:

18α(H)-trisnorneohopane;

Tm:

17α(H)-trisnorneohopane; C29H: C29 hopane; C30H: C30 hopane; 25-NH: C29 25-norhopane; C29Ts: C29 18α-30-norneohopane; G: gammacerane; (b) m/z 217: a: C21 pregnane; b: C22 homopregnane; c: 13β,17α-C27 diaserane(20S); d: 13β,17α-C27 diaserane(20R); e–p: 20S and 20R isomers for C27–C29 regular steranes; (c) m/z 231: C20: C20 triaromatic steroid; C21: C21 triaromatic steroid; C26–C28 20S, 20R: 20S and 20R isomers for triaromatic steroids with different carbon numbers; (d) m/z 177: C28N–C34N: 25-norhopanes with different carbon numbers; C28DNH: C28 28,30-dinorhopane.

Figure 3. Cross plots of G/C30H vs. C29 25-NH/C30H (a) and C30D/C30H (b), C29H/G vs. C28 25-NH/G (c), C30H/G vs. C29 25-NH/G (d), C28 25-NH/C29H vs. C28 25-NH/C30H ratios (e), summed concentrations of pentacyclic terpanes vs. C29 25-NH/C28 25-NH (f), and G/C30H vs. C29H/C30H (g) and C29Ts/C29H (h) ratios showing the different susceptibilities to biodegradation for hopanes and non-hopane compounds. G: gammacerane; 25-NH: 25-norhopane; C30D: C30 17α-diahopane; C29Ts: C29 18α-30-norneohopane; C29H: C29 hopane; C30H: C30 hopane.

Figure 4. Cross plot of summed concentration of pentacyclic terpanes vs. 22S/(22S+22R) ratios for C31~C35


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

homohopanes (a), and 22S/(22S+22R) ratios for C35 homohopane (b), C34 homohopane (c), C33 homohopane (d), C32 homohopane (e) and C31 homohopane (f) vs. their 25-norhomohopane counterparts to indicate the preferential depletion of 22siomer and 22R isomer.

Figure 5. Cross plots of summed TTs concentrations vs. (C20TT+C21TT)/C26TT (a), C22TT/C21TT (b), C24TT/C23TT (c), C26TT/C25TT (d), EE/LE C26TT (e), EE/LE C28TT (f), EE/LE C29 TT (g) and C24Tet/C26TT ratios (h) to show the different susceptibilities of TTs to biodegradation by carbon number and eluting orders. TT: tricyclic terpane; EE: early eluting; LE: late eluting; Tet: tentracyclic terpane.

Figure 6. Cross plots of pregnanes concentrations vs G concentrations (a) and C23TT concentrations (b), G concentrations vs. (αα+αββ)20S/(αα+αββ)20R (c) and C29 20S/(20S+20R) ratios (d), and diasteranes concentrations vs. C27DS/C27RS (e) and 20RC27/C29 ratios (f) to show the different susceptibilities of regular steranes and diasteranes to biodegradation. DS: diasterane; RS: regular sterane; TT: tricyclic terpane; G: gammacerane.

Figure 7. Cross plots of (C20+C21)/C26-28 with C26/C28 (20S) (a) and C27/C28 (20R) ratios (b) for Carboniferous oils at severe to extreme levels of biodegradation, showing preferential depletions of short-chained triaromatic steroids; (C20+C21)/C26–28: (C20 triaromatic steroid + C21 triaromatic steroid)/C26– 28

triaromatic steroids; C26/C28S: C26 triaromatic steroid(20S)/C28 triaromatic steroid(20S); C27/C28R: C27

triaromatic steroid(20R)/C28 triaromatic steroid(20R).


Page 16 of 25

Page 17 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

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Figure 1


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Figure 2


Page 18 of 25

Page 19 of 25

Figure 3 6.00

2.00 group A group B group C group D

group A group B group C group D

(a) 1.60

4.00

C30D/C30H

C2925-NH/C30H

5.00

3.00

(b)

1.20

0.80 2.00 0.40

1.00 0.00 0.00

1.00

2.00

3.00

4.00

0.00 0.00

5.00

1.00

2.00

G/C30H

5.00


(d) 3.00 C2925-NH/G

C2825-NH/G

3.00

2.00

1.00

2.00

1.00

0.00 0.00

1.00

2.00

3.00

0.00 0.00

4.00

1.00

2.00

C29H/G

3.00

4.00

C30H/G

6.00


0.80

(e)

(f)

0.70 C2925-NH/C2825-NH

C2925-NH/C30H

4.00


(c)

5.00

3.00

G/C30H

4.00

4.00 3.00 2.00

0.60 0.50 0.40 0.30 0.20

1.00 0.10 0.00 0.00

0.00 1.00

2.00

3.00

4.00

5.00

6.00

0

200

6.00 5.00


400

600

800

1000

1200

1400

1600

∑Penracyclic trepanes(µg/g)

C28 25-NH/C29H

1.00

(g) 0.80

4.00

C29-Ts/C29H

C29H/C30H

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

3.00


(h)

0.60

0.40 2.00 0.20

1.00 0.00 0.00

1.00

2.00

3.00

4.00

5.00

0.00 0.00

1.00

G/C30H

2.00 G/C30H


3.00

4.00

5.00

Energy & Fuels

Figure 4 C31

0.9

1500

C32

0.8

1400

C33

1300

C34

0.7

C35

1200

22S/(22S+22R)

∑Penracyclic trepanes(µg/g)

1600

1100 1000 900

0.6 0.5 HC35

0.4

NC34

0.3

800 0.2

(a)

700 600 0.00

0.1

0.20

0.40

0.60

0.80

1.00

(b)

0

22S/(22S+22R))

P661 P66 P666 P61 P663 P668 P60 P685 P665

0.6

0.8 0.7

0.5

0.4

0.3 HC34 0.2

NC33

22S/(22S+22R)

22S/(22S+22R)

0.6 0.5 0.4 HC33 0.3

NC32

0.2 0.1

(c)

0.1

0

P661 P66 P666 P61 P663 P668 P60 P685 P665

0.8

0.7

0.7

0.6

0.6

0.4 HC32 NC31

0.4 HC31

0.3

NC30 0.2

0.2 0.1

22S/(22S+22R)

0.5

0.5

0.3

(d)

0 P661 P66 P666 P61 P663 P668 P60 P685 P665

22S/(22S+22R)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 25

(e)

0

0.1

(f)

0 P661 P66 P666 P61 P663 P668 P60 P685 P665

P661 P66 P666 P61 P663 P668 P60 P685 P665


Page 21 of 25

Figure 5 4.00

0.70

(b)

(a)

3.50

0.60 0.50

2.50 C22TT/C21TT

(C20TT+C21TT)/C26TT

3.00

2.00 1.50 1.00

0.40 0.30 0.20 0.10

0.50 0.00

0.00 0

500

1000

1500 2000 ∑TTs(µg/g)

2500

3000

0

3.50

500

1000

1500 2000 ∑TTs(µg/g)

2500

3000

500

1000

1500 2000 ∑TTs(µg/g)

2500

3000

500

1000

2000

2500

3000

2000

2500

3000

4

(c)

3.00

(d)

3.5 3

2.50 C26TT/C25TT

C24TT/C23TT

2.5 2.00 1.50 1.00

2 1.5 1

0.50

0.5

0.00

0 0

500

1000

1500 2000 ∑TTs(µg/g)

2500

3000

0

1.60

2.00

(e)

1.40

(f)

1.80 1.60

1.20 EE/LE C28TT

EE/LE C26TT

1.40 1.00 0.80 0.60

1.20 1.00 0.80 0.60

0.40 0.40 0.20

0.20

0.00

0.00 0

500

1000

1500

2000

2500

3000

0

∑TTs(µg/g)

1500 ∑TTs(µg/g)

2.5

0.6

(g)

(h) 0.5

C24Tet/ C26TT

2

EE/LE C29TT

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

1.5

1

0.4 0.3 0.2

0.5

0.1

0

0 0

500

1000

1500

2000

2500

3000

0

500

∑TTs(µg/g)

1000

1500 ∑TTs(µg/g)


Energy & Fuels

Figure 6 250

700

(b)

(a)

600

200

C23TT (µg/g)

G (µg/g)

500 150

100

400 300 200

50 100 0

0 0

20

40

60 80 Pregnanes(µg/g)

100

0

120

250

40

60 80 Pregnanes(µg/g)

100

120

(d)

200

200

150

150

G (µg/g)

G (µg/g)

20

250

(c)

100

50

100

50

0 0.00

0.20 0.40 0.60 (αα+αββ) 20S/(αα+αββ) 20R

0.80

0 0.00

1.00

0.10

0.20

0.30

0.40

0.50

C29 20S/(20S+20R)

150

150

(e)

(f) 120 Diasterane(g/g)

120 Diasterane(µg/g)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 25

90

60

30

90

60

30

0

0 0

0.1

0.2

0.3

0.4

0.5

0.6

0

C27DS/C27RS

0.5

1 ααα20RC27/C29


1.5

2

Page 23 of 25

Figure 7 0.20


(a) 0.15 (C20+C21)/C26-28

0.15 (C20+C21)/C26-28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

0.10

0.05

0.00 0.00


(b)

0.10

0.05

0.05

0.10

0.15

0.20

0.00 0.00

0.20

C26/C28 20S

0.40

0.60

C27/C28 20R


0.80

1.00

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Page 24 of 25

Table 1 Strata

Density Viscosity NSO C22/C21 C24/C23 C26/C25 (C20+C21) C24Tet/ C29/ G/ C30D/ C28NH C29NH C30H C29H/ C29Ts/ C28NH 3 (g/cm ) (mPa•s) (%) TT /C26TT C26TT C30H C30H C30H /G /G /G G C29H /C29H TT TT

Well

Interval/m

P661

1106.2-1125.0 C

0.9288

149

16.27 0.23

0.52

3.11

2.10

0.24

0.79

0.54 0.14

0.83

0.61

1.85 1.47 0.16

0.56

P66

1109.06-1123. C

0.9285

154

17.12 0.19

0.50

2.76

3.57

0.24

0.70

0.49 0.16

0.79

0.59

2.03 1.41 0.19

0.56

P666

922.69-1140.77 C

0.9297

359

17.02 0.19

0.50

2.99

3.14

0.28

0.77

0.51 0.18

1.06

0.82

1.98 1.52 0.18

0.70

P61

855.73-949.58 C

0.9398

390

26.05 0.23

0.52

3.11

2.10

0.35

0.87

0.63 0.26

1.65

0.98

0.98 3.55 0.20

0.47

P663

928.45-1031

C

0.9528

1182

23.73 0.28

0.48

2.06

2.41

0.49

0.93

0.65 0.33

1.94

1.34

1.59 1.38 0.24

1.40

P668

953.15-1069.51 C

0.9528

1880

43.05 0.23

0.55

2.18

2.82

0.44

0.75

0.41 0.20

3.15

2.21

1.53 1.43 0.20

2.20

P60

690-800

C

0.9389

3079

34.94 0.35

0.76

1.47

0.52

0.46

3.61

1.10 0.66

2.34

1.65

0.23 1.82 0.14

1.28

P665

781.5-985.85

C

0.9590

8968

31.80 0.52

2.58

1.67

0.33

0.62

2.99

3.93 1.31

2.59

1.26

0.25 0.76 0.38

3.41

P685

808.82-892

C

0.9524

2600

28.18 0.59

2.96

3.81

0.20

0.57

5.09

4.27 1.85

2.64

1.34

0.23 1.19 0.26

2.21

Well

E/L E/L E/L C27/ C27DS/ (C21+C22)/ (αα+αββ) DS G C29NH/ C29NH/ 20S/ ∑PTs Ts/Tm C26/C28S C27/C28R 20S/20R (µg/g) (µg/g) (µg/g) C30H C28NH C26 C28 C29 C29RS (20S+20R) C27RS C26-28

P661

0.33

0.59

0.45

0.60 1.64 2.06 1.36

0.29

0.24

0.17

0.12

0.76

0.42

44.96 175.41 1478.11 2596.9

P66

0.29

0.52

0.57

0.69 0.97 1.08 0.60

0.44

0.06

0.15

0.12

0.72

0.72

115.02 139.3

P666

0.41

0.59

0.44

0.66 1.10 1.14 0.68

0.45

0.07

0.11

0.12

0.79

0.76

120.37 141.77 1313.7

P61

0.84

0.48

0.48

0.66 1.64 2.06 1.36

0.29

0.24

0.07

0.12

0.75

0.42

37.05 144.57 1218.28 2140.41 68.76

P663

1.44

0.65

0.60

1.37 1.79 1.65 1.59

0.21

0.52

0.06

0.12

0.77

0.36

44.04 129.12 1285.58 1452.22 64.23

P668

0.68

0.66

0.65

1.20 1.44 1.64 1.72

0.36

0.20

0.06

0.14

0.76

0.60

35.14 161.56 1353.03 1525.6

73.84

P60

0.99

2.13

0.62

0.85 1.28 0.63 1.33

0.35

0.33

0.04

0.15

0.76

0.38

/

/

/

/

/

P665

4.94

1.45

1.05

0.66 1.21 0.95 1.02

0.28

0.49

0.03

0.13

0.79

0.33

/

/

/

/

/

P685

5.71

2.59

0.90

0.69 1.23 0.96 1.04

0.29

0.47

0.04

0.12

0.75

0.36

27.76 220.18 945.75

780.71

103.28


∑TTs (µg/g)

Pregnane (µg/g) 83.42

1110.92 2825.58 62.29 2465.01 61.97

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