Whole-core analysis by 13C NMR

H. J. Vinegar, P. N. Tutunjian, W. A. Edelstein, P. B. Roemer

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

A whole-core nuclear magnetic resonance (NMR) system was used to obtain natural abundance 13C spectra. The system enables rapid, nondestructive measurements of bulk volume of movable oil, aliphatic/aromatic ratio, oil viscosity, and organic vs. carbonate carbon. 13C NMR can be used in cores where the 1H NMR spectrum is too broad to resolve oil and water resonances separately. A 5 1/4 -in. 13C/1H NMR coil was installed on a General Electric (GE) CSI-2T NMR imager/spectrometer. With a 4-in.-OD whole core, good 13C signal/noise ratio (SNR) is obtained within minutes, while 1H spectra are obtained in seconds. NMR measurements have been made of the 13C and 1H density of crude oils with a wide range of API gravities. For light- and medium-gravity oils, the 13C and 1H signal per unit volume is constant within about 3.5%. For heavy crudes, the 13C and 1H density measured by NMR is reduced by the shortening of spin-spin relaxation times. 13C and 1H NMR spin-lattice relaxation times were measured on a suite of Cannon viscosity standards, crude oils (4 to 60° API), and alkanes (C5 through C16) with viscosities of 77°F ranging from 0.5 cp to 2.5 × 107 cp. The 13C and 1H relaxation times show a similar correlation with viscosity from which oil viscosity can be estimated accurately for viscosities up to 100 cp. The 13C surface relaxation rate for oils on water-wet rocks is very low.

Original languageEnglish
Pages (from-to)183-189
Number of pages7
JournalSPE Formation Evaluation
Volume6
Issue number2
DOIs
StatePublished - 1 Jan 1991
Externally publishedYes

ASJC Scopus subject areas

  • Process Chemistry and Technology

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