IODP Expedition 337 Nuclear Magnetic Resonance Data Processing
Magnetic Resonance Measurement
The Combinable Magnetic Resonance Tool used in Expedition 337 measures the nuclear magnetic resonance properties of hydrogen in the formation. Initially, the hydrogen atoms are aligned in the direction of a static magnetic field (B0). The hydrogen atoms are then tipped by a short burst from an oscillating magnetic field that is designed so that they precess in resonance in a plane perpendicular to B0. The precession of the hydrogen atoms induces a signal in the tool antenna, and the decay of this signal is measured as the transverse relaxation time, T2. Because the formation contains hydrogen in different forms (in water in large pores, small pores, and bound in clay minerals, and in methane hydrate), there is a distribution of T2 times, here given from 0.3 ms to 3 s. The T2 distribution is the basic output of NMR measurement. It is further processed to give the total pore volume (the total porosity) and pore volumes within different ranges of T2, such as the bound and free fluid volumes.
See www.slb.com/-/media/files/fe/product-sheet/cmr-plus-ps and https://ux.uis.no/~s-skj/NMR/Schlumberger/O0_CMR_OilRev.pdf for a more detailed description of the tool and its applications.
Additional information:
Collett, T.S., 2001, Review of well-log analysis techniques used to assess gas-hydrate-bearing reservoirs: In Natural Gas Hydrates: Occurrence, Distribution, and Detection, American Geophysical Union, Geophysical Monograph 124, p. 189-210.
Horkowitz, J., Crary, S., Ganesan, K., Heidler, R., Luong, B., Morley, J., Petricola, M., Prusiecki, C., Speier, P., Poitzsch, M., Scheibal, J.R., and Hashem, M., 2002, Applications of a new magnetic resonance logging-while-drilling tool in a Gulf of Mexico deepwater development well: Proceedings of the Society of Professional Well Log Analyst Annual Logging Symposium, June 2-5, 2002, Paper EEE, 14p.
Data Quality
The NMR data quality is generally good. Data quality is affected, however, when the distance between the tool sensor and the wall of the borehole is greater than 1 inch. It is therefore recommended to look at the caliper measurement made by the density tool (CALI-TLD), which shows where the hole was enlarged and the tool was less likely to have made a good contact with the borehole wall.
Processed Data
The NMR data are presented in two ASCII files:
1) Files named 'nmr.dat' contain the following 1-D NMR log data:
BFV (%) : CMR bound fluid volume
CMFF (%): CMR free fluid volume (%): free fluid volume
CMRP_3MS (%): CMR 3 ms porosity
KSDR (mD): permeability from CMR (Schlumberger model)
KTIM (mD): permeability from CMR (Timur model)
TCMR (%): CMR total porosity
T2LM (ms): T2 Logarithmic mean
2) Files named ' t2dist.dat' contain the T2 distribution (spectra):
T2 (%): at each depth, values of % volume are given for 30 relaxation times (T2) ranging from 3 to 3000 msec. The scale is logarithmic, and T2 is given both in msec and as the log10 of the time in msec, from 0 to 29 (because this is a whole number, = 10 * log10(T2/3) ≠ 0.5).
Additional information about the drilling and logging operations can be found in the Operations and Downhole Measurements sections of the expedition report, Proceedings of the International Ocean Discovery Program, Expedition 337.
For questions about the database, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia
Tanzhuo Liu
Phone: 845-365-8630
Fax: 845-365-3182
E-mail: Tanzhuo Liu
For questions about the logs, please contact:
Yoshinori Sanada
E-mail: sanada@jamstec.go.jp
Yukari Kido
E-mail: ykido@jamstec.go.jp
Yuichi Shinmoto
E-mail: shinmoto@jamstec.go.jp