Zhao, H.; Li, Y.; Liu, W.; Zhang, G.; Wang, Y. The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1–3 during the Hydrocarbon Generation Process. Molecules2024, 29, 476.
Zhao, H.; Li, Y.; Liu, W.; Zhang, G.; Wang, Y. The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1–3 during the Hydrocarbon Generation Process. Molecules 2024, 29, 476.
Zhao, H.; Li, Y.; Liu, W.; Zhang, G.; Wang, Y. The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1–3 during the Hydrocarbon Generation Process. Molecules2024, 29, 476.
Zhao, H.; Li, Y.; Liu, W.; Zhang, G.; Wang, Y. The Dynamic Evolution Model of the Chemical and Carbon Isotopic Composition of C1–3 during the Hydrocarbon Generation Process. Molecules 2024, 29, 476.
Abstract
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.
Environmental and Earth Sciences, Geochemistry and Petrology
Copyright:
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