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1.
The petroleum generation potential and effective oil window of humic coals related to coal composition and age 总被引：1，自引：0，他引：1
A worldwide data set of more than 500 humic coals from the major coal-forming geological periods has been used to analyse the evolution in the remaining (Hydrogen Index, HI) and total (Quality Index, QI) generation potentials with increasing thermal maturity and the ‘effective oil window’ (‘oil expulsion window’). All samples describe HI and QI bands that are broad at low maturities and that gradually narrow with increasing maturity. The oil generation potential is completely exhausted at a vitrinite reflectance of 2.0–2.2%Ro or Tmax of 500–510 °C. The initial large variation in the generation potential is related to the original depositional conditions, particularly the degree of marine influence and the formation of hydrogen-enriched vitrinite, as suggested by increased sulphur and hydrogen contents. During initial thermal maturation the HI increases to a maximum value, HImax. Similarly, QI increases to a maximum value, QImax. This increase in HI and QI is related to the formation of an additional generation potential in the coal structure. The decline in QI with further maturation is indicating onset of initial oil expulsion, which precedes efficient expulsion. Liquid petroleum generation from humic coals is thus a complex, three-phase process: (i) onset of petroleum generation, (ii) petroleum build-up in the coal, and (iii) initial oil expulsion followed by efficient oil expulsion (corresponding to the effective oil window). Efficient oil expulsion is indicated by a decline in the Bitumen Index (BI) when plotted against vitrinite reflectance or Tmax. This means that in humic coals the vitrinite reflectance or Tmax values at which onset of petroleum generation occurs cannot be used to establish the start of the effective oil window. The start of the effective oil window occurs within the vitrinite reflectance range 0.85–1.05%Ro or Tmax range 440–455 °C and the oil window extends to 1.5–2.0%Ro or 470–510 °C. For general use, an effective oil window is proposed to occur from 0.85 to 1.7%Ro or from 440 to 490 °C. Specific ranges for HImax and the effective oil window can be defined for Cenozoic, Jurassic, Permian, and Carboniferous coals. Cenozoic coals reach the highest HImax values (220–370 mg HC/g TOC), and for the most oil-prone Cenozoic coals the effective oil window may possibly range from 0.65 to 2.0%Ro or 430 to 510 °C. In contrast, the most oil-prone Jurassic, Permian and Carboniferous coals reach the expulsion threshold at a vitrinite reflectance of 0.85–0.9%Ro or Tmax of 440–445 °C. 相似文献
2.
一种页岩含气性热演化规律研究的模拟实验方法 总被引：2，自引：1，他引：1
目前针对页岩气赋存规律研究的热模拟实验主要是沿袭常规油气热模拟方法,以粉末态样品开展模拟,研究对象为岩石生成并排出的烃类气体,这种模拟方式未明确页岩气的实质为"滞留气",并且模拟后样品无法开展扫描电镜分析,不能确定岩石孔隙结构变化规律。本文通过石英玻璃管封装块状样开展页岩生烃热模拟实验,并结合一套数据处理方法,尝试建立了一种适合页岩气研究的热模拟实验方法,研究泥页岩在不同演化阶段(Ro范围为0.596%~2.143%)不同赋存状态气体的含量以及岩石微观孔隙特征的变化情况。结果表明,泥岩及油页岩样品的排出气及解析气含量在高成熟度阶段(400℃以后)有明显增加的趋势,结合扫描电镜微观结构分析显示这是由于有机质生气量以及无机孔隙均有增加。本方法可以研究页岩热演化过程中不同赋存状态气体含量及微观孔隙结构的变化,为页岩气勘探开发提供了一种可参考的方法。 相似文献
3.
A series of methane (CH4) adsorption experiments on bulk organic rich shales and their isolated kerogens were conducted at 35 °C, 50 °C and 65 °C and CH4 pressure of up to 15 MPa under dry conditions. Samples from the Eocene Green River Formation, Devonian–Mississippian Woodford Shale and Upper Cretaceous Cameo coal were studied to examine how differences in organic matter type affect natural gas adsorption. Vitrinite reflectance values of these samples ranged from 0.56–0.58 %Ro. In addition, thermal maturity effects were determined on three Mississippian Barnett Shale samples with measured vitrinite reflectance values of 0.58, 0.81 and 2.01 %Ro.For all bulk and isolated kerogen samples, the total amount of methane adsorbed was directly proportional to the total organic carbon (TOC) content of the sample and the average maximum amount of gas sorption was 1.36 mmol of methane per gram of TOC. These results indicate that sorption on organic matter plays a critical role in shale-gas storage. Under the experimental conditions, differences in thermal maturity showed no significant effect on the total amount of gas sorbed. Experimental sorption isotherms could be fitted with good accuracy by the Langmuir function by adjusting the Langmuir pressure (PL) and maximum sorption capacity (Γmax). The lowest maturity sample (%Ro = 0.56) displayed a Langmuir pressure (PL) of 5.15 MPa, significantly larger than the 2.33 MPa observed for the highest maturity (%Ro > 2.01) sample at 50 °C.The value of the Langmuir pressure (PL) changes with kerogen type in the following sequence: type I > type II > type III. The thermodynamic parameters of CH4 adsorption on organic rich shales were determined based on the experimental CH4 isotherms. For the adsorption of CH4 on organic rich shales and their isolated kerogen, the heat of adsorption (q) and the standard entropy (Δs0) range from 7.3–28.0 kJ/mol and from −36.2 to −92.2 J/mol/K, respectively. 相似文献
4.
A new maturity parameter determined on both oil and bitumen samples, the asphaltene Tmax, is proposed and discussed. This parameter could be very useful to address the maturity of the source rock. The asphaltene Tmax is measured by programmed Rock-Eval pyrolysis, using a modified temperature program. Some phases of the experimental procedure, such as the asphaltene preparation and the Rock-Eval measurement substratum choice, are crucial in order to achieve reliable data. Laboratory simulations were carried out in order to assess the possible effects of both primary and secondary migration on asphaltene Tmaxin the expelled oil: the original value of the asphaltene Tmax in the bitumen is not substantially modified and it is very close to that measured on kerogen. Examples of the determination of asphaltene Tmax on many samples, collected from different areas and with different organic matter composition, are given. Results show that Tmax values from oil asphaltenes are reasonable indicators of source rock maturity. 相似文献
5.
Gas generation in the deep reaches of sedimentary basins is usually considered to take place via the primary cracking of short alkyl groups from overmature kerogen or the secondary cracking of petroleum. Here, we show that recombination reactions ultimately play the dominant role in controlling the timing of late gas generation in source rocks which contain mixtures of terrigeneous and marine organic matter. These reactions, taking place at low levels of maturation, result in the formation of a thermally stable bitumen, which is the major source of methane at very high maturities. The inferences come from pyrolysis experiments performed on samples of the Draupne Formation (liptinitic Type II kerogen) and Heather Formation (mixed marine-terrigeneous Type III kerogen), both Upper Jurassic source rocks stemming from the Norwegian northern North Sea Viking Graben system. Non-isothermal closed system micro scale sealed vessel (MSSV) pyrolysis, non-isothermal open system pyrolysis and Rock Eval type pyrolysis were performed on the solvent extracted, concentrated kerogens of the two immature samples. The decrease of C6+ products in the closed system MSSV pyrolysis provided the basis for the calculation of secondary gas (C1-5) formation. Subtraction of the calculated secondary gas from the total observed gas yields a “remaining” gas. In the case of the Draupne Formation this is equivalent to primary gas cracked directly from the kerogen, as detected by a comparison with multistep open pyrolysis data. For the Heather Formation the calculated remaining gas formation profile is initially attributable to primary gas but there is a second major gas pulse at very high temperature (>550 °C at 5.0 K min−1) that is not primary. This has been explained by a recondensation process where first formed high molecular weight compounds in the closed system yield a macromolecular material that undergoes secondary cracking at elevated temperatures. The experiments provided the input for determination of kinetic parameters of the different gas generation types, which were used for extrapolations to a linear geological heating rate of 10−11 K min−1. Peak generation temperatures for the primary gas generation were found to be higher for Heather Formation (Tmax = 190 °C, equivalent to Ro appr. 1.7%) compared to Draupne Formation (Tmax = 175 °C, equivalent to appr. Ro 1.3%). Secondary gas peak generation temperatures were calculated to be 220 °C for the Heather Formation and 205 to 215 °C for the Draupne Formation, respectively, with equivalent vitrinite reflectance values (Ro) between 2.4% and 2.0%. The high temperature secondary gas formation from cracking of the recombination residue as detected for the Heather Formation is quantitatively important and is suggested to occur at very high temperatures (Tmax approx. 250 °C) for geological heating rates. The prediction of a significant charge of dry gas from the Heather Formation at very high maturity levels has important implications for petroleum exploration in the region, especially to the north of the Viking Graben where Upper Jurassic sediments are sufficiently deep buried to have experienced such a process. 相似文献
6.
烂泥沟金矿是以浊积岩为容矿岩石的微细浸染型金矿。有机岩石学分析表明,矿石与围岩中干酪根类型无明显差别,同属腐泥-腐植型。与围岩相比,矿石中干酪根成熟度(R0=2.74%-3.06%)和含金性(6.15-24.8μg/g)均较高;干酪根总含金量在全岩中所占的比例是围岩高于矿石。氯仿沥青“A”的检测说明,矿石样品中可溶性有机质形成于强还原和高盐度环境,沥青质和含硫有机化合物发育。研究认为,干酪根含金性与碳的活化有关;不饱和的有机基因对金的动一定转换可能具有重要意义。 相似文献
7.
C.L. Riediger 《International Journal of Coal Geology》1993,22(3-4)
Marine, organic-rich rock units commonly contain little for vitrinite reflectance (VR0) measurement, the most commoly used method of assessing thermal maturity. This is true of the Lower Jurassic “Nordegg Member”, a type I/II, sulphur-rich source rock from the Western Canada Sedimentary Basin. This study examines the advantages and pitfalls associated with the use of Rock-Eval Tmax and solid bitumen reflectance (BR0) to determined maturity in the “Nordegg”. Vitrinite reflectance data from Cretaceous coals and known coalification gradients in the study area are used to extrapolate VR0 values for the “Nordegg”.Tmax increases non-linearly with respect to both BR0 and extrapolated VR0 values. A sharp increase in the reflectaance of both solid bitumen and vitrinite occurs between Tmax 440–450°C, and is coincident with a pronounced decrease in Hydrogen Index values and the loss of solid bitumen and telalginite fluorescence over the same narrow Tmax interval. This Tmax range is interpreted as the main zone of hydrocarbon generation in the “Nordegg”, and corresponds to extrapolated VR0 values of 0.55–0.85%. The moderate to high sulphur contents in the kerogen played a significant role in determining the boundaries of the “Nordegg” oil window.A linear relationship between BR0 and extrapolated VR0, as proposed elsewhere, is not true for the “Nordegg”. BR0 increases with respect to extrapolated VR0 according to Jacob's (1985) formula (VR0=0.618×(BR0)+0.40) up to VR0≈0.72% (BR0≈0.52%). Beyond this point, BR0 increases sharply relative to extrapolated VR0, according to the relatioship VR0 = 0.277 × (BR0) + 0.57 (R2 = 0.91). The break in the BR0−VR0 curve at 0.72%VR0 is thought to signifiy the peak of hydrocarbon generation and represents a previously unrecognized coalification jump in the solid bitumen analogous to the first coalification jump of liptinites. 相似文献
8.
The presence of partially oxidized algal organic matter in oil-prone marine source rocks, is the rule rather than the exception. Partially oxidized, algal kerogen can still act as a significant source of liquid hydrocarbons. However, the corresponding peak of C12 + hydrocarbon generation is shifted to a considerably lower maturity level compared with that of the classical Type II kerogen. The extent of primary alteration-oxidation of marine algal kerogen is monitored by means of solid state microfluorescence spectroscopy. A new parameter, the Primary Alteration Factor (PAF) is established, and the relationships between PAF and H/C, O/C, HI, TOC and between PAF and %0δ13C are determined. The present data show large variations in the bulk chemistry of immature marine algal kerogens, and reveal evidence for gradational dehydrogenation/oxidation of the source organic matter. This contrasts with the recently proposed mechanism for kerogen formation. SEM analysis reveals a relationship between the physical breakdown of algal organic matter and the formation of liptodetrinite. FTIR analysis shows that the incorporation of primary oxygen in the kerogen macromolecules is not in the form of carbonyl or carboxyl functionalities. The presence of highly unreactive, stable oxygen, associated with aromatic structures in partially oxidized algal kerogen, is suggested by resistance of the kerogen to graphitization. The FTIR data also suggest the presence of aryl ether oxygen. The present findings raise fundamental questions regarding the mechanisms of kerogen cracking and kerogen formation, and have important implications for petroleum exploration. 相似文献
9.
Organic matter maturity and oil/gas prospects in Middle-Upper Proterozoic and Lower Paleozoic carbonate rocks in northern China 总被引：3，自引：0，他引：3
Middle-Upper Proterozoic and Lower Paleozoic carbonate formations in northern China are well developed with an accumulative
thickness of 6000–1400 m. Both seepages and oils have been found in the outcrops and drilling wells.
The maturity of organic matter in these carbonate formations in obviously lower than that in southern China, as viewed from
reflectance (R°), H/C (atomic ratio), the amount and distribution of hydrocarbons,T
max°C and so on.T
max°C may be used as a principal index for determining the maturity of organic matter in carbonate rock-covered areas. According
to the results of themeasurement ofT
max°C andR° for natural samples and simulating experiments on bitumens from carbonate rocks, the limitation values for oil and gas have
been estimated at 455°C (R°=1.35) and 476°C(R°=2.25), respectively. On this basis, the map of organic matter maturity for the Middle-Upper Proterozoic, Ordovician, Cambrian
and Carboniferous of northern China has been compiled. It has been proposed that prospects of both oil and gas are expected,
with oil and condensate dominant in the Ordovician, and condensate and dry gas in the Middle-Upper Proterozoic. The Cambrian
is intermediate between them. 相似文献
10.
Hsien-Tsung Lee 《Environmental Earth Sciences》2011,64(7):1713-1728
The Rock-Eval pyrolysis and TOC analysis have been widely used to evaluate the source rock quality. The atomic H/C ratio of
kerogen, however, has been overlooked in source rock evaluation. In this study, coal and carbonaceous samples, including 26
from northwestern Taiwan, 12 from China, and 4 from the United States were analyzed, and integrated with 157 published data,
to explore the significance of atomic H/C ratio as a parameter of source rock evaluation. Two different linear trends were
observed in the cross-plot of S
1 versus S
2. Field outcropped shale or C-shale exhibits a steeper slope compared to that of coal samples which can be attributed to the
compositional difference in their organic material. A rather strong positive correlation for H% versus S
2 illustrates the contribution of H-containing macerals, especially exinite. Organic matters in the samples studied are of
type II/III kerogen based on the relationship between HI and T
max. The H/C ratio, as well as the HI, S
1, and S
2, generally decreases with the maturity increasing. The H/C ratio decreases slightly from 1.1 to 0.7 with the maturity increasing
from R
o 0.55 to 0.85%. Samples with H/C ratio in this range show significant change in certain other geochemical parameters (e.g.
HI, S
1, S
2, S
1 + S
2, S
1/(S
1 + S
2), S
1/TOC, (S
1 + S
2)/TOC, T
max). The (S
1 + S
2)/TOC ratio (defined as QI) was used as an indicator of the hydrocarbon potential. The QI, HI, and H/C ratio show a certain
correlation, all increasing accordingly. The QI of the samples analyzed in this study is approximately 100–380 (mgHC/gTOC),
similar to that of most humic coals for oil and gas generation. Samples with R
o value lower than 0.55% always show significant variation in their HI, ranging from 80 to 520 mgHC/gTOC. It is inferred that
hydrocarbon potential started from R
o 0.55% and atomic H/C ratio 1.1 in this study. 相似文献
11.
Yoshihiro Uji 《Organic Geochemistry》1986,9(6)
This study examines the effect of contact metamorphism by an igneous dyke on parameters for kerogen maturation, such as elemental composition (H/C, O/C, N/C), 1H-NMR T1, vitrinite reflectance and infrared spectra. Although elemental composition and 1H-NMR T1 of the kerogen changed only within 1.5 and 5.0 m from the dyke respectively, vitrinite reflectance of the kerogen was thermally affected beyond 10.0 m from the intrusion. It is concluded that vitrinite reflectance is the most sensitive of the parameters evaluated to assess thermal stress of kerogens. 相似文献
12.
Jian-bing Xu Bin Cheng Qian Deng Yun-gan Liang Oluwabamise Lekan Faboya Ze-wen Liao 《中国地球化学学报》2018,37(6):886-900
There is a dearth of information about the distribution of trace elements in kerogen from shale rocks despite several reports on trace element composition in many shale samples. In this study, trace elements in shale rocks and their residual kerogens were determined by inductively coupled plasma–mass spectrometry. The results from this study show redox-sensitive elements relatively concentrated in the kerogens as compared to the shales. This may be primarily due to the adsorption and complexation ability of kerogen, which enables enrichment in Ni, Co, Cu, and Zn. For the rare earth elements (REEs), distinct distribution characteristics were observed for shales dominated by terrigenous minerals and their kerogen counterparts. However, shales with less input of terrigenous minerals showed similar REE distribution patterns to their residual kerogen. It is speculated that the distribution patterns of the REEs in shales and kerogens may be source-related. 相似文献
13.
14.
J. Jochum 《Mineralium Deposita》2000,35(5):451-464
A mechanical decrepitation device coupled with a gas chromatograph has been used to characterize the molecular composition
of gaseous and liquid hydrocarbons contained in minerals. Application of this technique allows the identification of low-molecular-weight
n-alkanes and some aromatic hydrocarbons in sulfides and gangue minerals from epigenetic Variscan and post-Variscan lead–zinc
deposits in the Rhenish Massif, Germany. Based on the analysis of 200 samples, Variscan and post-Variscan mineralization can
be distinguished by the composition of associated hydrocarbons. Variscan sulfides and gangue minerals contain high abundancies
of methane. In contrast, n-alkanes in the C2–C9 range and aromatic hydrocarbons (benzene, toluene) are dominant in post-Variscan mineralization. The absence of high-molecular-weight
hydrocarbons in ore minerals suggests highly mature gas associated with hydrothermal activity, during which hydrothermal fluids
caused an increase in thermal maturation of organic matter and the generation of low-molecular-weight hydrocarbons in the
adjacent organic-rich rocks. The hydrocarbon compositions contained in fluid inclusions of Variscan and post-Variscan minerals
are probably governed by the maturation level of the potential source rocks. In Variscan time tectonic brines (T > 175 °C) generated predominantly methane, whereas basement brines (T < 175 °C) expelled higher-molecular-weight hydrocarbons (wet gases, condensates, aromatic hydrocarbons) from adjacent rocks
during the Mesozoic event. The specific role of hydrocarbons in sulfide precipitation via thermochemical sulfate reduction
is indicated by geochemical characteristics of organic matter associated with the Plombières Pb–Zn deposit, in eastern Belgium.
Intense alteration phenomena were observed in near-ore kerogens, compared with unaltered kerogens far from the ore body, as
well as by a very high maturity (5.40% Ro), a systematic depletion in 12C towards the vein-type mineralization, high atomic S/C ratios (0.49), and by low atomic H/C ratios (0.29). The data suggest
that hydrothermal solutions caused a drastic increase in the thermal maturation of organic matter within the adjacent wall
rock. Increased thermal maturation resulted in increased δ13C-values of organic carbon due to the preferential release of 12C. The change in the organic matter to a H-depleted and S-enriched bulk composition in association with sulfide ores strongly
suggests that thermochemical sulfate reduction was responsible for organic degradation. Thus, thermochemical sulfate reduction
probably triggered base metal sulfide precipitation in Variscan and post-Variscan ore deposits of the Rhenish Massif. Finally,
based on data from this study and previous investigations, new genetic models are presented for both Variscan and post-Variscan
mineralization in the Rhenish Massif.
Received: 15 September 1999 / Accepted: 2 December 1999 相似文献
15.
Noriyuki Suzuki 《Geochimica et cosmochimica acta》1984,48(2):243-249
A preliminary attempt to fractionate amorphous kerogens from terrigenous bulk kerogen by a benzene-water two phase partition method under acidic condition was made. Microscopic observation revealed that amorphous kerogens and structured kerogens were fractionated effectively by this method. Characteristics of the amorphous and structured kerogens fractionated by this method were examined by some chemical analyses and compared with those of the bulk kerogen and humic acid isolated from the same rock sample (Haizume Formation, Pleistocene, Japan). The elemental and infrared (IR) analyses showed that the amorphous kerogen fraction had the highest atomic ratio and the lowest atomic ratio and was the richest in aliphatic structures and carbonyl and carboxyl functional groups. Quantities of fatty acids from the saponification products of each geopolymer were in agreement with the results of elemental and IR analyses. Distribution of the fatty acids was suggestive that more animal lipids participate in the formation of amorphous kerogens because of the abundance of relatively lower molecular weight fatty acids (such as C16 and C18 acids) in saponification products of amorphous kerogens. On the other hand, although the amorphous kerogen fraction tends to be rich in aliphatic structures compared with bulk kerogen of the same rock samples, van Krevelen plots of elemental compositions of kerogens from the core samples (Nishiyama Oil Field, Tertiary, Japan) reveal that the amorphous kerogen fraction is not necessarily characterized by markedly high atomic ratio. This was attributed to the oxic environment of deposition and the abundance of biodegraded terrestrial amorphous organic matter in the amorphous kerogen fraction used in this work. 相似文献
16.
Weili Wang Luofu Liu Zhenxue Jiang Ningning Zhong Ying Wang Ping Wang Lin Wu Jianghui Meng Jieli Zhou Yongqiang Guo 《中国地球化学学报》2011,30(4):405-414
The Western Depression of the Liaohe Basin is the major exploration area of the Liaohe Oilfield, and its main source rocks consist of the third and fourth members of the Shahejie Formation (Es3 and Es4). These source rocks are widely distributed in the depression, with semi-deep lake and fan delta as the main sedimentary facies, brown oil shale and black gray-dark gray mudstone as the main rocks, and a total thickness of 270-1450 m. The kerogens are mainly of the types I and IIA, and partly of the type IIB and least of the type III. The Ro values range from 0.4%-0.8%, indicating an evolution stage from immature to mature. The maturity of Es4 source rocks is rela-tively high, reaching the early mature stage, but their distribution and thickness are lower than those of Es3. Besides, according to biomarker analysis, it is thought that the source rocks of Es3 and Es4 are characterized by mixed input, and most of the source rocks were formed in the brackish water-saline and strongly oxygen-free environment. Fur-thermore, the Qingshui, Niuxintuo and Chenjia sags are believed to possess greater potential for hydrocarbon gen-eration and expulsion, for they are source rocks with a larger thickness, have higher organic carbon contents, belong to better organic matter types and possess higher maturities. 相似文献
17.
D型菌解无定形体的形成及其生烃模式 总被引：1，自引：0，他引：1
通过对准噶尔盆地部分油藏烃源岩的电子显微镜研究,在大量样品中检出D型菌解无定形体,其母质来源具有二元混合性,形成在弱还原─原环境中,生烃门限Ro值为0.4%,生烃期大约为0.4%-0.7%,是轻质油(或凝析油)和天然气形成的重要组分之一。在低演化阶段,由于细菌参加了对有机质的改造,使ⅡB-Ⅲ类烃源岩中富集氢,生烃能力变好。文章还初步探讨了芳烃化合物含量与菌解无定形体D形成的关系,指出当沉积体系中的硫和硫化氢与铁结合,形成稳定的黄铁矿物后,才有可能在Ⅲ型有机质中形成高含量的D型菌解无定形体。 相似文献
18.
High maturity oil and gas are usually generated after primary oil expulsion from source rocks, especially from oil prone type I/II kerogen. However, the detailed impacts of oil expulsion, or retention in source rock on further thermal degradation of kerogen at the high maturity stage remain unknown. In the present study, we collected an Ordovician Pingliang shale sample containing type II kerogen. The kerogens, which had previously generated and expelled oil and those which had not, were prepared and pyrolyzed in a closed system, to observe oil expulsion or oil retention effects on later oil and gas generation from kerogen. The results show that oil expulsion and retention strongly impacts on further oil and gas generation in terms of both the amount and composition in the high maturity stage. Gas production will be reduced by 50% when the expulsion coefficient reaches 58%, and gas from oil-expelled kerogen (less oil retained) is much drier than that from fresh kerogen. The oil expulsion also causes n-alkanes and gas compounds to have heavier carbon isotopic compositions at high maturity stages. The enrichment of 13C in n-alkanes and gas hydrocarbons are 1‰ and 4–6‰ respectively, compared to fresh kerogen. Oil expulsion may act as open system opposite to the oil retention that influences the data pattern in crossplots of δ13C2–δ13C3 versus C2/C3, δ13C2–δ13C3 versus δ13C1 and δ13C1–δ13C2 versus ln(C1/C2), which are widely used for identification of gas from kerogen cracking or oil cracking. These results suggest that the reserve estimation and gas/source correlation in deep burial basins should consider the proportion of oil retention to oil expulsion the source rocks have experienced. 相似文献
19.
This study presents data on the composition of organic matter from the Late Silurian sediments of the Chernov uplift. These sediments are characterized by low Corg contents, which may reach 1–3% in individual layers. A relatively high thermal maturity of organic matter is confirmed by polycyclic biomarker distributions and Rock-Eval pyrolyisis data. Despite its higher thermal maturity level (T max = 456°C), kerogen in carbonaceous shales from the Padymeityvis River exhibits good preservation of long-chain n-alkyl structures, which are readily identified in the 13C NMR spectra and by the molecular analysis of the kerogen pyrolysis products. 相似文献
20.
Ying-Ju Chang 《Geochimica et cosmochimica acta》2008,72(15):3771-3787
The evolution of fluorescence has been measured for “live” oils generated from 14 oil-prone kerogens or coals from varying depositional environments during closed system pyrolysis in a diamond anvil cell at three heating rates (3, 8, and 25 °C/min), and temperatures up to 600 °C. The measured fluorescence intensities of the samples, employing using violet excitation at 405 nm, increases significantly during maturation intervals within the oil window, while the fluorescence spectra of oils generated from all studied kerogens exhibit progressive blue-shift of peak wavelengths (λmax) and red/green quotients (I650/I500) upon increasing maturity. The observed trend is consistent with a maturity dependence of the spectral shift, which is widely recognized in natural hydrocarbon inclusions and crude oils using ultraviolet (UV) excitation (365 nm). The data presented herein suggest that the λmax of spectra for inclusion oils shift in similar direction despite differences in composition or source kerogen. This implies that the reverse or anomalous trends reported for inclusion oils in nature may be attributed to other processes, which significantly alters the fluorescence properties of oils subsequent to their generation. Oils with the similar color (λmax or I650/I500) can be derived from diverse kerogens with maturities that vary by ±0.3% Ro, suggesting that the fluorescent colors of crude and inclusion oils are both maturity- and source-dependent, and therefore cannot be used as universal maturity indicators. In addition, the blue-shifts observed for cumulative oils generated from all kerogens approaches similar minima λmax values around the green-yellow wavelength (564 nm) and at I650/I500 values around 0.6, at maturities close to the middle or late stage of oil generation. This suggests that most late-stage cumulative oils will exhibit similar colors. Oils generated during late-stage maturity intervals, however, can exhibit colors with shorter wavelengths. 相似文献