Study of the Mechanism for Identifying the Shale Gas ‘Sweet Spot’ Using the Reversed δ13C1‐3 Series

Zhao, Heng; Luo, Hao; Guchun, Zhang,; Wang, Yanjun; Qin, Yunhu; Zhang, Dongdong; Liu, Wenhui

doi:10.1111/1755-6724.14663

Cited by 2 publications

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“…The chemical and isotopic composition of light hydrocarbons have long been used to study the origins, generation, accumulation, and degradation process of hydrocarbons in the past decades [1][2][3][4][5][6][7][8][9]; however, with the large-scale exploration, development, and Molecules 2024, 29, 476 2 of 15 study of the intensive isotopic geochemistry of natural gas resources in the high evolution strata of superimposed basins, it is increasingly difficult to clearly identify the origin and evolutionary process of hydrocarbons by the chemical and isotopic characteristics of alkanes. This is because there are many factors and geochemical processes responsible for the chemical and isotopic compositions of hydrocarbons in geological conditions, such as the inheritance of isotopic signatures from precursor organics, kinetic isotope fractionations, and equilibrium isotope fractionations, and the mixing of hydrocarbons from different origins and of different maturities.…”

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confidence: 99%

The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1–3 during the Hydrocarbon Generation Process

Zhao,

Li,

Liu

et al. 2024

Molecules

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A new approach is presented in this paper for the dynamic modeling of the chemical and isotopic evolution of C1–3 during the hydrocarbon generation process. Based on systematic data obtained from published papers for the pyrolysis of various hydrocarbon sources (type I kerogen/source rock, type II kerogen/source rock, type III kerogen/source rock, crude oil, and asphalt, etc.), the empirical evolution framework of the chemical and isotopic composition of C1–3 during the hydrocarbon generation process was built. Although the empirical framework was built only by fitting a large amount of pyrolysis data, the chemical and isotopic composition of C1–3 derived from the pyrolysis experiments all follow evolution laws, convincing us that it is applicable to the thermal evolution process of various hydrocarbon sources. Based on the simplified formula of the isotopic composition of mixed natural gas at different maturities (δ13Cmixed), δ13Cmixed = X×niA×δ13CiA+Y×niB×δ13CiBX×niA+Y×niB, it can be derived that the cumulative isotopic composition of alkane generated in a certain maturity interval can be expressed by the integral of the product of the instantaneous isotopic composition and instantaneous yield at a certain maturity point, and then divided by the cumulative yield of alkane generated in the corresponding maturity interval. Thus, the cumulative isotopic composition (A(X)), cumulative yield (B(X)), instantaneous isotope (C(X)), and instantaneous yield (D(x)) in the dynamic model, comply with the following formula during the maturity interval of (X0~X). A(X) = ∫X0XCX×DXdxB(X), where A(X) and B(X) can be obtained by the fitting of pyrolysis data, and D(x) can also be obtained from the derivation of B(X). The dynamic model was applied on the pyrolysis data of Pingliang Shale to illustrate the quantitative evolution of the cumulative yield, instantaneous yield, cumulative isotope, and instantaneous isotope of C1–3 with increasing maturity. The dynamic model can quantify the yield of methane, ethane, and propane, as well as δ13C1, δ13C2, and δ13C3, respectively, during the hydrocarbon generation process. This model is of great significance for evaluating the natural gas resources of hydrocarbon source rock of different maturities and for identifying the origin and evolutionary process of hydrocarbons by chemical and isotopic data. Moreover, this model provides an approach to study the dynamic evolution of the isotope series of C1–3 (including reversed isotopic series), which is promising for revealing the mechanism responsible for isotopic reversal when combined with post-generation studies.

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Section: Introductionmentioning

confidence: 99%

The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1–3 during the Hydrocarbon Generation Process

Zhao,

Li,

Liu

et al. 2024

Molecules

Self Cite

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show abstract

The Dynamic Evolution Model of Chemical and Carbon Isotopic Composition of C1-3 during the Hydrocarbon Generation Process

Zhao,

Li,

Liu

et al. 2024

Preprint

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A new approach is presented for dynamic modeling of chemical and isotopic evolution of C1-3 during the hydrocarbon generation process. Based on systematic data obtained from published papers for pyrolysis of various hydrocarbon sources(type I kerogen/source rock, type II kerogen/source rock, type III kerogen/source rock, crude oil, asphalt, etc), the empirical evolution framework of chemical and isotopic composition of C1-3 during the hydrocarbon generation process was built. Although the empirical framework was built only by fitting large amount of pyrolysis data, the chemical and isotopic composition of C1-3 derived from the pyrolysis experiments all follow the evolution laws, convincing us that it is applicable to the thermal evolution process of various hydrocarbon sources. Based on the simplified formula of the isotopic composition of mixed natural gas at different maturities (δ13Cmixed) δ13Cmixed=(X〖*n〗_iA 〖*δ〗^13 C_iA+Y〖*n〗_iB 〖*δ〗^13 C_iB)/(X〖*n〗_iA+Y〖*n〗_iB ), it can be derived that the cumulative isotopic composition of alkane generated in certain maturity interval can be expressed by the integral of the product of instantaneous isotopic composition and instantaneous yield at certain maturity point, and then divided by the cumulative yield of alkane generated in corresponding maturity interval. Thus, the cumulative isotopic composition(A(X)), cumulative yield(B(X)), instantaneous isotope(C(X)),and instantaneous yield(D(x)) in the dynamic model comply with the following formula during the maturity interval of (X0-X) A(X)=(∫_(X_0)^X▒〖C(X)*D(X)dx〗)/(B(X)), where A(X) and B(X) can be obtained by fitting of pyrolysis data, and D(x) can also be obtained from the derivation of B(X). The dynamic model was applied on the pyrolysis data of Pingliang Shale to illustrate the quantitative evolution of cumulative yield ,instantaneous yield, cumulative isotope and instantaneous isotope of C1-3 with increasing maturity.The dynamic model can quantify the yield of methane, ethane and propane as well as δ13C1, δ13C2 and δ13C3 respectively during the hydrocarbon generation process, which is of great significance to evaluate the natural gas resources of hydrocarbon source rock with different maturity and to identify the origin and evolutionary process of hydrocarbons by chemical and isotopic data. Moreover, this model provides an approach to study the dynamic evolution of isotope series of C1-3 (including reversed isotopic series), which is hopeful to reveal the mechanism responsible for isotopic reversal when combined with post-generation studies.

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Study of the Mechanism for Identifying the Shale Gas ‘Sweet Spot’ Using the Reversed δ¹³C_1‐3 Series

Cited by 2 publications

References 0 publications

The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1–3 during the Hydrocarbon Generation Process

The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1–3 during the Hydrocarbon Generation Process

The Dynamic Evolution Model of Chemical and Carbon Isotopic Composition of C<sub>1-3</sub> during the Hydrocarbon Generation Process

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