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TitleMethane isotherms and magnetic resonance imaging in shales
AuthorDick, M J; Heagle, D; Veselinovic, D; Green, D
SourceThe 2019 International Symposium of the Society of Core Analysts (SCA 2019); by Schembre-McCabe, J (ed.); Ott, H (ed.); E3S Web of Conferences vol. 146, 05004, 2020 p. 1-10, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20190570
PublisherEDP Sciences
MeetingThe 2019 International Symposium of the Society of Core Analysts (SCA 2019); Pau; FR; August 26-30, 2019
Mediapaper; on-line; digital
File formatpdf
Subjectsfossil fuels; geophysics; Science and Technology; Economics and Industry; energy resources; petroleum resources; hydrocarbons; hydrocarbons, light; gas; methane; thermal analyses; reservoir rocks; bedrock geology; lithology; sedimentary rocks; shales; hydrocarbon recovery; enhanced recovery; fluid flow; resource estimation; permeability; pore size; Methodology
Illustrationstables; schematic diagrams; photographs; plots; time series
Released2020 02 05
AbstractAdsorption isotherms of light hydrocarbons on reservoir rocks are key data used to quantify the total gas content in reservoirs and isotherms are now being used to improve our understanding of the processes affecting subsurface gas flow associated with gas injection from Enhanced Oil Recovery techniques. This project combined elements of the traditional pressure-volume gas adsorption isotherm technique and an NMR-based adsorption isotherm approach to determine the adsorption isotherms of light hydrocarbons on to tight rocks from oil and gas reservoirs. The new approach allows isotherms to be derived from NMR data. First, a T2 distribution of the gas is determined over a range of gas pressures. Next, the volume of pore gas is estimated using the pore volume of the rock and the Van der Waals gas equation. The adsorbed gas content is then calculated by subtracting pore gas content from the total gas content. This is repeated for a range of gas pressures to determine the adsorption isotherm. This project used the NMR method described above and measured the gas pressure decay in the NMR cell. This combined approach includes the advantages of the NMR method but it also produces a pressure-time curve that can be used to identify when equilibrium is attained in low permeability rocks and can be used to compare adsorption kinetics of different gases. The advantages of our approach are that 1) the samples remain intact and the measurements provide information on the pore size distribution; 2) analyses can be carried out at reservoir pressures; 3) isotherms can be measured for any gas containing hydrogen atoms; and 4) the results can be used to examine the processes controlling gas flow through the rock. Future work to develop this technique will improve our quantification of the amount of pore gas in the cell, which will improve our partitioning between adsorbed gas and pore gas as well as allow for an improved analysis of the pressure response of the sample after degassing.
Summary(Plain Language Summary, not published)
This publication focuses on a technique for understanding how gases interact with rocks in oil and gas reservoirs. Specifically, it looks at how light hydrocarbons are adsorbed onto these rocks, which is important for estimating the amount of gas in reservoirs and improving gas injection methods used in Enhanced Oil Recovery.
The researchers combined traditional methods with a newer approach that uses Nuclear Magnetic Resonance (NMR) to determine how gases are adsorbed onto tight rocks. The NMR approach provides advantages like keeping the rock samples intact and working at reservoir pressures. It can also be used with various gases containing hydrogen atoms.
By using this combined approach, the researchers can analyze the pore size distribution in the rocks and study how gases are adsorbed at different pressures. This information helps improve our understanding of gas flow in these rocks.
The scientific impact of this work is significant because it enhances our ability to study and optimize gas storage and extraction processes in reservoir rocks. It can lead to more efficient and effective methods for Enhanced Oil Recovery and better estimates of the gas content in reservoirs, which is crucial for the energy industry.

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