Using rock-eval S4Tpeak as thermal maturity proxy for shales

Hazra, Bodhisatwa; Singh, Deependra Pratap; Chakraborty, Prasenjeet; Singh, Pradeep K.; Sahu, S.G.; Adak, A.K.

doi:10.1016/j.marpetgeo.2021.104977

Cited by 33 publications

(15 citation statements)

References 16 publications

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“…Very recently, the S4T peak has been documented as a reliable thermal maturity proxy for shales. 59 Although the HI of the BS sample (230 mg HC/g TOC; presence of Type-II−III admixed kerogen) is much lower than the LS, it must be noted that the sample BS is marked by the presence of Type-II−III admixed kerogen. It is reasonably established that Type-II kerogen has higher liquid hydrocarbongenerating capacity even at lower thermal maturity levels.…”

Section: Resultsmentioning

confidence: 94%

“…Similar to S 2 T max , the S 4 T peak also showed contrasting values for the two shales, further substantiating their distinct thermal maturities. Very recently, the S 4 T peak has been documented as a reliable thermal maturity proxy for shales …”

Section: Resultsmentioning

confidence: 99%

“…From the raw data generated, the peak temperature of the S4CO 2 curve was calculated to determine S4T peak , which has recently been proposed as a proxy to assess thermal maturity in shales. 59 Thermogravimetry of the LS and BS shales was conducted in a simultaneous thermal analyzer (STA 409C, NETZSCH, Germany) to obtain the thermogravimetry (TG-DTG) and differential scanning calorimetry (DSC) thermograms. The samples were weighed to about 20 ± 0.1 mg, then placed in a crucible, and heated from room temperature up to 750 °C at a heating rate of 10 °C/min under an air atmosphere.…”

Section: Methodsmentioning

confidence: 99%

“…Similarly, since the BS sample was collected from the Raniganj basin (Permian age; oil window mature), a lower sample weight was used to calculate the TOC precisely (following Hazra et al , ). From the raw data generated, the peak temperature of the S 4CO 2 curve was calculated to determine S 4 T peak , which has recently been proposed as a proxy to assess thermal maturity in shales …”

Section: Methodsmentioning

confidence: 99%

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Impact of Degassing Time and Temperature on the Estimation of Pore Attributes in Shale

et al. 2021

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The influence of degassing time and temperature on low-pressure gas adsorption (LPGA) behavior of shales was examined in this study. Two organic-rich shales of contrasting maturity, reactivity and organic matter type, were crushed to <1 mm and <212 μm grain-sizes and degassed at 110, 200, and 300 °C for 3 and 12 h, respectively. Our results indicate that degassing duration has a minimal influence on pore-character interpretations from LPGA experiments, while the degassing temperature shows a strong influence on the pore attributes. For both shales, reliable porosity estimates were obtained when the samples were degassed at 110 °C. When the degassing temperature was increased to 200 and further to 300 °C, distinct changes in adsorption isotherms and other pore structural features were observed. For the mesoporous low-mature shale (collected from a lignite mine) when the degassing temperature was kept at 200 °C, a macroporous character was induced with a manifold increase in pore diameter. Results from thermogravimetry and Rock-Eval indicate abundance of reactive kerogen, which undergoes alteration when degassed at higher temperatures. When the degassing temperature was kept at 300 °C, the organic matter underwent further alteration and showed an isotherm similar to the shales degassed at 110 °C. Similarly, for the oil-window mature shale sample, a transition towards macroporous structure was observed when the sample was degassed at 200 and 300 °C, compared to a mesoporous structure observed when degassed at 110 °C. The results from fractal dimensions also support the above inferences, indicating the presence of simpler structures at higher degassing temperatures. Reduction in pore volume (110–200 °C) and its further rise (200–300 °C) are also evident in the micropore domain, more distinctly in the oil window mature shale. Our results strongly indicate that degassing temperature should be kept at around 110 °C for reliable shale pore character estimation.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Impact of Degassing Time and Temperature on the Estimation of Pore Attributes in Shale

et al. 2021

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“…The details of the Rock-Eval technique and modifications made over the years are detailed in Lafargue et al, Behar et al, Carvajal-Ortiz et al, and Hazra et al For the purpose of analysis, crushed samples of <212 μm size were loaded into the crucibles, automatically inserted into the pyrolysis oven and analyzed using the “Basic/Bulk Rock method”. Sample weights used followed the revised guidelines for avoiding Flame Ionization Detector (FID) saturation to provide reliable total organic carbon (TOC) estimation. − During the pyrolysis-stage (first-stage), the samples are first heated under isothermal conditions (300 °C) for 3 min, which releases the free hydrocarbons present in the samples, recorded as the S1 curve. This is followed by ramped heating (at 25 °C/min) during which two processes happen simultaneously: (a) cracking of kerogen to generate hydrocarbons (detected by FID and recorded as the S2 curve) and (b) cracking of oxygenated compounds (detected by infrared detector and recorded as the S3 curve).…”

Section: Methodsmentioning

confidence: 99%

Pore Properties in Organic-Rich Shales Derived Using Multiple Fractal Determination Models Applied to Two Indian Permian Basins

et al. 2021

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The pore geometry of shale reservoirs plays an important role in the storage and transportation of petroleum in these unconventional resources. Intrinsic surface roughness, indicated by fractal dimensions and contrasting pore size distributions of shales are primary factors that influence shale's fluid flow and resource volume characteristics. The Frenkel−Halsey−Hill (FHH) derived fractal dimensions are widely applied for evaluating the pore structural complexities of shales. In this work, for a suite of shales samples collected from two Permian basins, India, with distinct maturities, low pressure nitrogen gas adsorption−desorption has been employed to elucidate the pore structural framework. Three alternative fractal calculation methods (FHH, Neimark, and Wang−Li) are compared to provide further insight into the fractal characteristics of the shales. Ambiguities are revealed in the selection of the most appropriate fractal values. Fractal dimensions calculated by the FHH and Wang−Li methods are in relatively close agreement (ranging between 2.5 and 2.8) and the small systematic differences between their values can be explained in terms of fitting errors and assumptions associated with both methods. However, the Neimark fractal values are unreasonable (>3 for all the samples). Thermal maturity is a key controlling feature of the pore structural facets and fractal dimensions of the Raniganj basin samples (T max = 431−463 °C) but not for North Karanpura (T max = 434−442 °C) samples. Strong correlations exist between calculated fractal dimensions and specific surface area, pore volume, and average pore radius for all samples. However, systematic differences in these values between the samples from the two basins are most likely explained in terms of their mineralogical differences, specifically the higher kaolinite content of the Raniganj samples.

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