Logging Plan
The logging program is designed to measure physical properties, hole shape, and to determine in situ stress, porosity, and fracture characteristics of the rock and sediment around the hole, which is important for a site intended for a long-term seismic observatory. The Formation MicroScanner will provide a detailed, oriented resistivity image of the borehole, including fractures and conductive zones. Temperature logs will be emphasized for identification of permeable zones and inflow/outflow from both drilling-induced and natural fractures in the hole. The spontaneous potential (SP) log will provide in situ measurement of the streaming potential, which is related to electrochemical and electrokinetic changes and pore-water flow in permeable formations. The ultrasonic borehole imager (UBI) will be used to characterize the shape and volume of the borehole in the vicinity of the seismometers. This will significantly improve success in grouting of the instruments. The UBI will also be used for the determination of breakouts for directional measurements of the in situ stress field. The dual laterolog (DLL) will permit a good characterization of highly resistive rocks from the oceanic basement because of its wide resistivity range.
At proposed Site WP-1B, we will run the standard triple-combo tool string, the FMS/sonic tool
string (with a repeat pass in the basement interval), the DLL tool string, and the UBI in the
basement interval. The triple combo tool string includes the natural gamma-ray sonde (NGS) to
measure the natural radioactivity, the accelerator porosity sonde (APS) to measure porosity, the
hostile environment lithodensity sonde (HLDS) to measure density, and the Dual Induction tool
(DIT-E) to measure resistivity. The triple combo tool string also measures the spontaneous
potential and makes a caliper measurement. The FMS/sonic tool string includes the Formation
MicroScanner, the dipole shear sonic imager (DSI), and a natural gamma-ray tool (NGT). The
DLL will be run with the NGT. We anticipate that it will take 38 hr for logging operations at Site
WP-1B.