Table 1. Summary of results of prior CORKs in accretionary settings.
|Barbados Ridge (Hole 949C)||Oregon Margin (Hole 892B)|
|Zone monitored||Décollement at ~400 mbsf nearly spanned by screened section||Thrust fault that intersects BSR updip; at site, BSR behind casing ~40 m shallower than thrust fault|
|Period monitored||3.5 years: July 1994--Jan. 1998||2 years: Nov. 1992--Nov. 1994|
|In situ pressures||1.02 MPa stable overpressure (<~3MPa lithostatic)||Very low P (13kPa)|
Higher P drained at drilling?
|In situ temperatures||Stable at geothermal gradient||Stable, but transient event in fault|
|Fluid flow transients?||No significant natural transients - pressure transients due to pump testing and LWD||Warming of thermistor in fault zone indicated transient upfault flow of warm fluids|
|Hydrological testing||Permeability varies several magnitudes with effective stress|
(Screaton et al., 1995, 1997; Fisher and Zwart, 1996)
|Fluid sampling||Despite high P, low permeability prohibited fluid production at valve||No, low P; later produced gas hydrates, after data logger removed|
|Tidal loading - attenuation||85% of seafloor amplitude, consistent with muddy sediments of 60% porosity above décollement||More attenuated, consistent with more cemented, lithified formation|
|Tidal loading - phase||Dispersive phase lag - requires weak formation outside screened interval, later verified with LWD||Slight phase lead confirmed presence of free gas|
|Main citation||Becker et al., 1997||Davis et al., 1995|
Primary Operations Plan and Time Estimate | Table of Contents