Integrated NMR Core and Log Investigations With Respect to ODP LEG 204

HR: 1340h
AN: OS23A-1531 [Abstracts]
TI: Integrated NMR Core and Log Investigations With Respect to ODP LEG 204
AU: * Arnold, J
EM: j.arnold@geophysik.rwth-aachen.de
AF: Applied Geophysics, RWTH Aachen University , Lochnerstr. 4-20 , Aachen, 52056
AU: Pechnig, R
OS23A-1531 AF: Applied Geophysics, RWTH Aachen University , Lochnerstr. 4-20 , Aachen, 52056
AU: Clauser, C
OS23A-1531 AF: Applied Geophysics, RWTH Aachen University , Lochnerstr. 4-20 , Aachen, 52056
AU: Anferova, S
OS23A-1531 AF: Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 1, Aachen, 52056
AU: Bl［ich, B
OS23A-1531 AF: Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 1, Aachen, 52056
AB: NMR techniques are widely used in the oil industry and are one of the most suitable methods to evaluate in-situ formation porosity and permeability. Recently, efforts are directed towards adapting NMR methods also to the Ocean Drilling Program (ODP) and the upcoming Integrated Ocean Drilling Program (IODP). We apply a newly developed light-weight, mobile NMR core scanner as a non-destructive instrument to determine routinely rock porosity and to estimate the pore size distribution. The NMR core scanner is used for transverse relaxation measurements on water-saturated core sections using a CPMG sequence with a short echo time. A regularized Laplace-transform analysis yields the distribution of transverse relaxation times T2. In homogeneous magnetic fields, T2 is proportional to the pore diameter of rocks. Hence, the T2 signal maps the pore-size distribution of the studied rock samples. For fully saturated samples the integral of the distribution curve and the CPMG echo amplitude extrapolated to zero echo time are proportional to porosity. Preliminary results show that the NMR core scanner is a suitable tool to determine rock porosity and to estimate pore size distribution of limestones and sandstones. Presently our investigations focus on Leg 204, where NMR Logging-While-Drilling (LWD) was performed for the first time in ODP. Leg 204 was drilled into Hydrate Ridge on the Cascadia accretionary margin, offshore Oregon. All drilling and logging operations were highly successful, providing excellent core, wireline, and LWD data from adjacent boreholes. Cores recovered during Leg 204 consist mainly of clay and claystone. As the NMR core scanner operates at frequencies higher than that of the well-logging sensor it has a shorter dead time. This advantage makes the NMR core scanner sensitive to signals with T2 values down to 0.1 ms as compared to 3 ms in NMR logging. Hence, we can study even rocks with small pores, such as the mudcores recovered during Leg 204. We present a comparison of data from core scanning and NMR logging. Future integration of conventional wireline data and electrical borehole wall images (RAB/FMS) will provide a detailed characterization of the sediments in terms of lithology, petrophysics and, fluid flow properties.
DE: 3004 Gas and hydrate systems
DE: 3022 Marine sediments: processes and transport
DE: 3036 Ocean drilling
DE: 3094 Instruments and techniques
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005