TEMPERATURE-TWO PRESSURE (T2P) PROBE
Geometry of the "Temperature-Two Pressure" (T2P) probe. Pore pressure and temperature are measured at the end of the tip extension and the base of the shaft. |
The Temperature-2-Pressure penetrometer was developed jointly by University of Texas at Austin and MIT to measure in-situ pore pressure and temperature in sediments at the base of a borehole. Tool development began in 2003; it was land-tested in 2004 and deployed on the IODP's JOIDES Resolution drillship in June 2005 on IODP Expedition 308. The T2P is approximately eight feet long and decreases in diameter from ~2.75" at the base to a narrow tip, which houses a thermistor and pressure sensor; a second pressure sensor is located at the larger diameter shaft behind the tip (thus 1 temperature and 2 pressure or "T2P"). The probe is driven into a formation and left in-place measuring the dissipation of temperature and pressure on an onboard computer. Following Expedition 308, it was determined that an improvement to the Colleted Delivery System would be required to produce optimal results. The subsequent improvement to the delivery system is now the 'Motion De-Coupled Hydraulic Delivery System' (MDHDS). As part of this improvement, the T2P required physical modification to its diametric size. To meet this reduction, the IODP Texas A&M developed the Common Data Acquisition (CDAQ) system for the T2P. After rigorous laboratory and field testing the T2P and engineering team completed a successful round of engineering tests on IODP Expedition 342 in June 2012. Currently the T2P is housed at the University of Texas and is available for deployment. After undergoing rigorous laboratory and field testing, the UT research team deployed the latest version of the probe, along with a new delivery system (the Motion De-coupled Hydraulic Delivery System or MDHDS) at sea in June of 2012 on IODP Expedition 342. The T2P and MDHDS have greatly improved in-situ temperature and pressure measurements. Prior to the MDHDS, penetrometers were deployed using the Colleted Delivery System. With this system, failure due to premature removal occurred 80% of the time (due to ship heave), additionally, it was difficult to align the tool during penetration resulting in bent or broken tips. Now, with the MDHDS and re-designed T2P, a more slender tool delivered through a well-designed delivery system results in near perfect execution, with no bent or broken tips, every time.
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