Underway Geophysics | Table of Contents
LOGGING PLAN
The logging program is designed to measure physical properties and hole shape and to determine in situ stress, porosity, and fracture characteristics of the rock and sediment around the hole. These determinations are important for a site as a long-term seismic observatory. The Formation MicroScanner (FMS) will provide a detailed 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 grouting procedures for the instruments.
At Site WP-2A, we will run the standard triple-combo tool string, the FMS/sonic tool string, and, if time permits, the UBI. The triple combo tool string includes the natural gamma-ray sonde (NGS) to measure 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 and the dipole shear sonic imager (DSI), along with a natural gamma-ray tool (NGT). We anticipate that it will take ~33 hr for logging operations (two runs of each tool string) at Site WP-2A.