Determination of in situ hydrocarbon contents in shale oil plays. Part 1: Is routine Rock–Eval analysis reliable for quantifying the hydrocarbon contents of preserved shale cores?

Li, Jinbu; Wang, Min; Xu, Liang; Li, Ming; Yu, Changqi; Wu, Yan; Lu, Shuangfang

doi:10.1016/j.orggeochem.2022.104449

Cited by 23 publications

(11 citation statements)

References 22 publications

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“…We speculate that organic maturation and hydrocarbon generation do not result in large δ 15 N variations in expelled oil over a wide range of temperatures. This small variance in δ 15 N during maturation in the presence of a progressive loss of TN kerogen (Figure ) calls for essentially nonfractionating mechanisms of N org elimination, which is quite different from Rayleigh fractionation caused by traditional element loss processes, such as the observed δ 13 C of oil. ,− …”

Section: Discussionmentioning

confidence: 96%

Behavior of Nitrogen Contents and Isotopes during Thermal Evolution and Hydrocarbon Generation in Shale: Insights from Hydrothermal Experiments in a Semiopen System

Xu,

Shen,

Chen

et al. 2024

ACS Earth Space Chem.

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Nitrogen is an important component of petroleum systems. However, nitrogen loss and fractionation processes during the thermal evolution of organic matter are not conclusive. Moreover, current studies have focused mainly on single components, such as bulk rock, kerogen, or crude oil, but the relationships between them have not been systematically studied. A series of hydrothermal experiments were conducted, and data were collected from 69 geological samples. The results illustrate that the nitrogen isotope compositions (δ15N) of different nitrogen-containing components vary with simulated temperature. The δ15Nex‑bulk (δ15N of bulk rock after extraction) continuously increased, with the largest change reaching 2.4‰. The δ15Nkerogen (δ15N of kerogen) basically remained constant until 400 °C (R o < 1.78%), and the δ15Noil (δ15N of expelled oil) changed by only 0.6‰ throughout the oil generation phase. A comparison of the data for δ15Nex‑bulk and δ15Nkerogen reveals that the relationship between them is affected by thermal evolution. Below 400 °C, the δ15Nkerogen value is greater than δ15Nex‑bulk, and these differences decrease with increasing temperature. However, above 400 °C, the relationship reverses to δ15Nkerogen lower than δ15Nex‑bulk, and the difference between them increases with the temperature. The difference between them can serve as a rough maturity indicator. In addition, the comparison of δ15Noil and δ15Nkerogen reveals that thermal evolution has little effect on the δ15Noil, which indicates that the δ15Noil has the potential to preserve the original information on organic matter.

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Section: Discussionmentioning

confidence: 96%

Behavior of Nitrogen Contents and Isotopes during Thermal Evolution and Hydrocarbon Generation in Shale: Insights from Hydrothermal Experiments in a Semiopen System

Xu,

Shen,

Chen

et al. 2024

ACS Earth Space Chem.

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“…The higher degree of S 1 loss in Bakken shale can be attributed to its superior porosity and permeability compared to Chang7 shale, as denser shales are more effective at retaining light oil fractions (Gao et al, 2018; Jarvie et al, 2012). Other lacustrine shales, such as the Qingshankou shale in the Songliao Basin (Li et al, 2022), the Qianjiang shale in the Jianghan Basin (Qian et al, 2022), and the Funing shale in the Subei Basin (Liu et al, 2023), had average S 1 values of 5.94, 5.23, and 1.96 mg/g for fresh samples, respectively, with corresponding average S 1 values of 3.49, 3.11, and 0.95 mg/g for old samples, resulting in S 1 losses of 41%, 41%, and 52%, respectively (Figure 10). The differences in S 1 loss among these lacustrine shales are not significant and are all lower than that observed in the marine Bakken shale, indicating that these lacustrine shales are denser than Bakken shale.…”

Section: Discussionmentioning

confidence: 99%

“…Pyrolysis S 1 values and S 1 loss for the Chang7 shale in the Ordos Basin (Zhao et al, 2023), Bakken shale in the Williston Basin (Jarvie et al, 2012), Qingshankou shale in the Songliao Basin (Li et al, 2022), Qianjiang shale in the Jianghan Basin (Qian et al, 2022), and Funing shale in the Subei Basin (Liu et al, 2023). …”

Section: Discussionmentioning

confidence: 99%

“…As a result, intervals of petroleum migration and accumulation in reservoirs are enriched in short-chain n-alkanes and saturated hydrocarbons compared to their corresponding source-rock intervals (Han et al, 2015(Han et al, , 2019Leythaeuser et al, 1988;Zou et al, 2019). When the amount of oil generated by organic matter exceeds the adsorption capacity of organic matter and F I G U R E 1 0 Pyrolysis S 1 values and S 1 loss for the Chang7 shale in the Ordos Basin (Zhao et al, 2023), Bakken shale in the Williston Basin (Jarvie et al, 2012), Qingshankou shale in the Songliao Basin (Li et al, 2022), Qianjiang shale in the Jianghan Basin (Qian et al, 2022), and Funing shale in the Subei Basin (Liu et al, 2023).…”

Section: Impact Of Petroleum Loss On Shale Oil Compositionmentioning

confidence: 99%

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Impact of petroleum expulsion and evaporation losses on shale oil assessment using pyrolysis techniques

You,

Liu,

Song

et al. 2023

Geological Journal

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Shale reservoirs contain petroleum that undergoes losses through oil expulsion and evaporation, with uncertain implications on shale oil reserves and mobility evaluation. This study focuses on understanding the influence of these losses on open‐system pyrolysis, the primary method for assessing shale oil content and mobility. Comprehensive analyses were performed on 26 lacustrine shale samples from the Chang7 Member, encompassing total organic carbon (TOC), programmed pyrolysis, solvent extraction, and gas chromatography–mass spectrometry (GC–MS). The research examines the impact of petroleum losses on petroleum fractions, the oil saturation index (OSI), and multi‐step pyrolysis outcomes. The findings indicate that Chang7 shale with TOC content above 7% experiences more substantial petroleum losses than those with TOC below 7%. Petroleum losses result in significant fractional distillation of crude oil in the shale, leading to the deterioration of shale oil properties and a notable reduction in free oil content in S1, ultimately causing a decline in OSI values. As a result, Chang7 shale with TOC below 7% demonstrates a higher potential for shale oil recovery, whereas Chang7 shale with TOC exceeding 7% should be considered more significant as a hydrocarbon source rock. Moreover, multi‐step pyrolysis is not suitable for assessing petroleum mobility in shale with low free oil content (OSI values below 100 mg/g). This limitation arises from the loss of free low‐boiling components in Chang7 shale, and the currently detected low‐boiling pyrolysis products may predominantly exist in an adsorbed state.

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“…On one hand, when the shale is brought from the underground to the surface, small molecular hydrocarbons will release due to sudden changes in temperature and pressure (Chen and Jiang, 2020). On the other hand, sample storage, pretreatment such as crushing, and Rock-Eval crucible waiting process also lead to evaporation of light components (Jarvie, 2014;Li et al, 2022a). Generally speaking, the loss of light hydrocarbons is related to its their proportion in shale oil, and the higher the proportion, the greater the loss (Noble et al, 1997;Ma et al, 2024).…”

Section: Introductionmentioning

confidence: 99%

Research on loss rules of oil and gas in preserved shale cores after open air exposure

Zhang,

Wang,

et al. 2024

Front. Earth Sci.

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There is a large amount of oil and gas loss in traditional conventional core samples. Revealing the rules of oil and gas loss is of great significance for restore the pristine oil content and oil component in the shale. In this study, four preserved shale cores with different thermal maturity (Ro = 1.01–1.53%) and different total organic carbon content (TOC = 1.69–5.48 wt.%) were selected. The samples are obtained from the first member of the Qingshankou Formation in the Gulong Sag. Nuclear magnetic resonance (NMR) T1–T2 mapping and thermal desorption gas chromatography (TD–GC, at a constant temperature of 300°C for 3 min) were performed on the preserved cores and their replicas that were exposed in open air for different times, to study dynamic loss process and the molecular composition changes of shale oil. The results show that during exposure, shale experiences a large amount of oil loss, with a loss ratio of about 42%–78%, and the higher the maturity, the greater the loss ratio. The oil loss is mainly contributed by free oil, with a loss ratio as high as 88%. The adsorbed oil content, however, remains basically unchanged and has a good positive correlation with the TOC of shale. Once the cores were crushed, the gaseous hydrocarbon in oil was basically evaporated in just 5 min. After long-term storage, 90% of the C14- light hydrocarbon is lost, while the C14+ heavy hydrocarbon experiences basically no loss. Therefore, effective and timely analysis of preserved shales is extremely important. The oil content of uncrushed shale cores characterized by NMR T1–T2 mapping is much greater than that of the crushed sample measured by TD-GC, which means that NMR T1–T2 mapping can be important method to evaluate the original fluid saturation of shale.

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Determination of in situ hydrocarbon contents in shale oil plays. Part 1: Is routine Rock–Eval analysis reliable for quantifying the hydrocarbon contents of preserved shale cores?

Cited by 23 publications

References 22 publications

Behavior of Nitrogen Contents and Isotopes during Thermal Evolution and Hydrocarbon Generation in Shale: Insights from Hydrothermal Experiments in a Semiopen System

Behavior of Nitrogen Contents and Isotopes during Thermal Evolution and Hydrocarbon Generation in Shale: Insights from Hydrothermal Experiments in a Semiopen System

Impact of petroleum expulsion and evaporation losses on shale oil assessment using pyrolysis techniques

Research on loss rules of oil and gas in preserved shale cores after open air exposure

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