All sites will be logged with the triple-combo geophysical and formation microscanner (FMS)/sonic (sonic digital tool [SDT]) combination tools to which the temperature tool (TLT) will be added. The triple-combo (DIT-HLDS-APS) will provide three independent porosity estimates by measuring the electronic density (hostile environment lithodensity sonde [HLDS]), the hydrogen density (accelator porosity sonde [APS]), and the electrical resistivity (phasor dual induction tool [DIT]). The dual laterolog (DLL) may be required to measure electrical resistivity in the basement if the basement turns out to be very resistive. The FMS will provide oriented images of drilling induced tensile fractures and natural fractures for stress analysis, for structural analysis, and core/log integration.

The geological high-sensitivity magnetometer (GHMT), if on board, may be used at Site ACE-9a to aid core/log integration via magnetic susceptibility. The borehole televiewer (BHTV) will be run in the deeper section of Sites ACE-3c and 8a to ultrasonically image lithostratigraphy, fracture orientation, and the presence and extent of borehole breakouts.

At Site ACE-8a, the Schlumberger five-element array seismic imager (ASI) will be used in the cased hole for a VSP to accurately tie the well to the MCS data. In addition, a drill-string straddle packer will be used to isolate two perforated intervals within the cemented casing and, perhaps, one interval within the open borehole below the casing. The three isolated intervals will be above, within, and below the fault zone. Once the packers are set, the isolated interval will be allowed to equilibrate to obtain the best possible estimate of formation pore pressures. Subsequently, pulse tests will be conducted to estimate formation permeabilities. If injected pulses decay very rapidly, indicating high formation permeability, constant-rate flow tests will be conducted. The longer duration tests allow for greater radius of influence and more reliable permeability estimates. Following the hydrogeologic tests in Site ACE-8a, the interval will be hydraulically fractured for the purpose of measuring the least principal stress magnitude (Shmin). These tests will consist of at least two cycles of fluid injection and shut-in, followed by bleeding off excess pressure.

Details of the complete stress tensor will be inferred from hydraulic fracture experiment (Shmin), pore pressure estimates, and images (BHTV and FMS) of tensional (tensile cracking) and compressive (wellbore breakouts) failures. Repeated temperature profiles from logging may provide evidence for fluid flow associated with critically stressed fractures and faults. These temperature profiles will also help constrain the thermal perturbations, enabling the development of drilling-induced tensile cracking. Interactions between breakouts and fractures/faults may also be used to constrain the extent of stress perturbation associated with active faulting (Barton and Zoback, 1994).

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