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TitleAdsorbed and free hydrocarbons in unconventional shale reservoir: a new insight from NMR T1-T2 maps
AuthorLi, J; Jiang, CORCID logo; Wang, M; Lu, S; Chen, ZORCID logo; Chen, G; Li, ZORCID logo; Lu, S
SourceMarine and Petroleum Geology vol. 116, 104311, 2020 p. 1-14,
Alt SeriesNatural Resources Canada, Contribution Series 20190553
Mediapaper; on-line; digital
File formatpdf; html
AreaBeijing; China
Lat/Long WENS 115.0000 119.5000 38.0000 36.0000
Subjectsfossil fuels; geochemistry; Science and Technology; Nature and Environment; petroleum resources; hydrocarbon potential; hydrocarbons; oil; bedrock geology; lithology; sedimentary rocks; shales; sedimentary basins; analytical methods; core samples; organic geochemistry; observation wells; porosity; Paleogene; Eocene; Jiyang Depression; Bohai Bay Basin; Zhanhua Sag; Dongying Sag; Shahejie Formation; Methodology; Phanerozoic; Cenozoic; Tertiary
Illustrationsplots; location maps; geoscientific sketch maps; stratigraphic columns; lithologic sections; schematic diagrams; tables; spectra
ProgramGeoscience for New Energy Supply (GNES) Canadian Energy Geoscience Innovation Cluster (CEGIC)
Released2020 02 25
AbstractCharacterizing free and adsorbed hydrocarbon is crucial for the resources assessment and mobility evaluation of shale oil plays. The complex feature of hydrogen-bearing components in shale reservoirs requires new analytical methods to study the occurrences of different states of hydrocarbons. In this study, forty core samples from five shale oil research wells in the Jiyang Depression of China were analyzed using various analytical tools including nuclear magnetic resonance (NMR) T1-T2 mapping, Leco total organic carbon (TOC) analysis, routine and special programmed Rock-Eval pyrolysis, solvent extraction and fractionation, as well as mercury injection capillary pressure (MICP) experiments. Additional experiments were conducted on a powdered shale for NMR T1-T2 maps under four states: as-received, after being dried at 110 °C, after special programmed pyrolysis to 350 °C, and after solvent extraction. The results showed that residual water signals in the NMR T1-T2 map disappeared after being dried at 110 °C. Free oil signals decreased dramatically when the sample was thermally treated to 350 °C, while adsorbed oil signals decreased sharply after solvent extraction. A good accordance was observed between the organic hydrogen T2 spectra and three modes of Rock-Eval pyrograms, representing free hydrocarbons, adsorbed hydrocarbons, and hydrocarbons from kerogen/bitumen decomposition. A positive correlation was also found between the intensity of NMR T1-T2 map signals and the free and adsorbed hydrocarbon contents from geochemical analysis. T2 cut-off values of adsorbed hydrocarbons and free hydrocarbons were determined to be 0.2 ms and 1 ms, respectively. Core samples with a high oil saturation index, porosity, and relative content of hydrocarbons display a low T1/T2 ratio indicative of a high shale oil mobility. As a complementary method to the Rock-Eval analysis, NMR T1-T2 mapping is a non-destructive technique for the characterization of adsorbed and free hydrocarbons at the core scale with limited sample preparation. The results of this study are helpful for NMR characterization of shale reservoirs.
Summary(Plain Language Summary, not published)
Proton nuclear magnetic resonance (NMR) T1-T2 mapping was used in this study to investigate the amounts of free and adsorbed oil in shale samples. The results obtained were found to show a positive linear relationship with those from thermal analysis. Compared with thermal analysis, NMR technique has the advantage of requiring minimal sample preparation and being non-destructive to the samples.

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