LOGGING PLANDownhole logging measurements will provide in situ formation properties for the H2O observatory site. These properties include density, porosity, resistivity, temperature, K, Th, and U contents, elastic properties, and hole condition estimates. The planned logging program includes the standard geophysical string (triple combo), the FMS/sonic string, the well seismic tool (WST), and the borehole compensated (BHC) sonic string.
The triple combo tool string includes the natural gamma ray sonde (NGS) to measure 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 Lamont-Doherty Earth Observatory temperature tool (TLT) is also attached to the triple combo string. Temperature logs will be emphasized for identification of permeable zones and inflow/outflow from both drilling-induced and natural fractures in the holes.
The FMS/sonic string includes the Formation MicroScanner (FMS) and the dipole shear sonic imager (DSI). The high-resolution (centimeter scale) FMS image log can help to identify large- and small-scale lithologic units and tectonic features (presence of fractures and faults, their orientations, and their degree of alteration). Comparison of fractures detected from these log images could provide information on the lateral extension of the fracture system beyond the borehole and the significance of borehole-induced features vs. natural fractures. The FMS caliper log could also be used for hole size estimation. The DSI tool provides both compressional and shear wave data.
WST (or WST-3 if available) will be used to provide normal incident VSP data for the proposed objectives. However, its deployment depends upon the time constraints and the hole penetration. The BHC sonic log will be used for the cased interval of basement to obtain the acoustic properties of the formation through casing and to check the integrity of the cement.
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