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doi:10.2204/iodp.proc.308.203.2008

Appendix A

Davis-Villinger Temperature-Pressure Probe

In “Appendix A,” we present the DVTPP deployments during Expedition 308, which includes five sections: (1) instruments that were used; (2) temperature calibration; (3) pressure calibration; (4) example DVTPP deployment showing the detailed deployment procedure; and (5) detailed description of each DVTPP deployment. Figures showing pressure, temperature, and TrueView data for each DVTPP deployment are in the “APP_A” folder in “Supplementary material.”

Instruments

During Expedition 308, two data logger/​pressure transducer/​thermistor combinations were used: (1) logger 9368-PXDCR 88579-thermistor 0226-2 (DVTPP2) and (2) logger 9367-PXDCR 88587-thermistor 0226-3 (DVTPP3). In the “DOWNHOLE” folder in “Supplementary material,” PXDCR 79481 and thermistor 0226-1 were listed together with logger 9367. However, this is not correct.

Temperature calibration

Temperature calibrations were carried out on the data logger and the thermistor separately. The data logger response to resistance was determined using a highly stable resistance box that simulates the resistance variation of the thermistor over its full temperature range. The calibration coefficients of the data logger were provided by the U.S. Implementing Organization (USIO) (Table AT1A). Table AT1B presents the commercial calibration of the thermistors. The Steinhart-Hart relationship is used to describe the temperature as a function of the thermistor resistance (Table AT1A) (Davis et al., 1997).

During Expedition 308, the DVTPP temperature data were not always reduced correctly. For example, the DVTPP3 temperature data was calibrated using the calibration coefficients of thermistor 0226-1 (see the “DOWNHOLE” folder in “Supplementary material”). However, thermistor 0226-1 was not used in either of the DVTPP tools that were deployed during Expedition 308. This problem was also reported during IODP Expedition 311 (A.M. Tréhu, pers. comm., 2007). In a similar fashion for DVTPP2, the temperature calibrations of several deployments were done using coefficients of thermistor 0226-1 or 0226-3 instead of 0226-2 (see the “DOWNHOLE” folder in “Supplementary material”). In this report, we recalculated the temperature for all deployments using the correct calibration coefficients provided by the USIO (Table AT1).

Pressure calibration

The calibration factors for all pressure transducers are illustrated in Table AT2. The calibration factors of the pressure transducers are stored in the central processing unit of the pressure interface module mounted to the DVTPP logger. Two frequency (or period) output signals are sent from the pressure transducer. Pressure is measured with a force-sensitive quartz crystal whose output period changes with applied load. A second period output comes from a quartz crystal temperature sensor used for temperature compensation. The last calibration of the two transducers was made in 2002 by the manufacturer (Table AT2).

In December 2006, the USIO performed a calibration verification of the DVTPP pressure transducers using a deadweight tester that was recently calibrated by the manufacturer. DVTPP2 and DVTPP3 recorded pressures 7 and 4 psi greater, respectively, than that measured by the deadweight tester. In this report, we subtracted the average atmosphere pressure recorded by the DVTPP from the pressure data. After the correction, the calibration offsets are excluded and the DVTPP pressure is comparable to the hydrostatic pressure calculated from an assumed seawater density of 1.024 g/cm3 in which the atmosphere pressure is not accounted.

DVTPP deployment procedure

Every DVTPP deployment is slightly different. We present DVTPP Deployment 20 to illustrate our approach to interpreting the deployment history. This deployment was at 175 mbsf in Hole U1322D. The operational sequence for this deployment is illustrated in Table AT3, and a graphical representation of the pressure, temperature, coreline depth, block position, accelerometer, pump strokes, coreline tension, and hookload are illustrated in FIGUREA1_1322D04.XLS in the “APP_A” folder in “Supplementary material.” For reasons that we do not understand, some of the bit depth data shifted during deployment. Instead, we use the traveling block position to constrain movements of the drill bit during tool deployment whenever it is available. The traveling block is attached to the top end of the drill string above the rig floor. Its position was recorded in meters above rig floor.

Prior to deployment, the BHA was located 5.5 m above the bottom of the hole (BOH). The DVTPP was connected to the CDS and lowered into the borehole with the wireline (Event 1). The DVTPP was stopped at the seafloor for 5 min to record the fluid pressure and temperature in the pipe (Event 2). Fluid circulation was stopped during the tool stop to remove the effect of pump pressure on the measured pressure. The pump flux is proportional to the pump stroke rate (1.654 gal/stroke) (Graber et al., 2002).

The CDS was then lowered by wireline (Event 3). At this time, the CDS was fully extended and hanging inside the drill pipe. The BHA was moved downward to 7 m above BOH (Event 4). As the CDS approached the BHA, it was decelerated and slowly lowered to latch into the BHA. This can be identified by a sharp decrease in coreline tension (Event 5). For this deployment, when fully extended the CDS was 21.84 m including the DVTPP probe. When the CDS was fully retracted, the tip of the DVTPP extended 1.1 m below the BHA. This length can vary depending on how many spacers (92 cm long) are connected to the DVTPP. The CDS was retracted ~2 m when latched in (Event 5).

Next, the BHA was lowered to further retract the CDS stoke (Event 6). The probe was pushed into the formation. This induced increases in pressure and temperature after the CDS was fully retracted. The operator stopped the insertion when the hookload dropped by ~5,000 lb (Event 7), indicating that the BHA reached BOH or that the formation is too firm for further penetration. In this case, the probe was pushed ~1.1 m into the formation. Subsequently, the BHA was raised 2.4 m and the CDS was partially extended to decouple the DVTPP from the BHA (Event 8).

In this deployment, the tool was left in place for 60 min. Tool acceleration was recorded during the deployment, which is a measure of tool movement during the dissipation phase. The tool was then recovered by wireline (Event 9) and stopped at the mudline for 5 min to register the fluid pressure in the pipe (Event 10).

DVTPP deployments during Expedition 308

Deployment 1: Hole U1320A, 203.4 mbsf

Table AT4 and FIGUREA2_1320A24.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 1. Fluid circulation was kept on for the entire deployment. The tool was stopped at the seafloor for 10 min to record the fluid pressure in the pipe. When the probe was pushed into the formation, the temperature and pressure increased. After the penetration pressure pulse, the pressure decreased rapidly and erratically. The last pressure reading was 1 MPa less than the hydrostatic pressure.

We interpreted that this was caused by an internal hydraulic leak in the DVTPP; when pressure reached a high value, fluid leaked into the pressure housing, causing a rapid decrease. The pressure then slowly increased and leakage once again occurred. Because of the internal leak, no in situ pressure can be ascertained. Unfortunately, this internal leak was not identified and fixed until DVTPP Deployment 4. The temperature record appears reasonable. The last temperature reading was 10.2°C. However, the accelerometer recorded slight tool movement throughout the dissipation phase. The tool movements resulted in a very slight oscillation (magnitude < 0.01°C, period ≈ 50 s) in the temperature record. This suggests minor coupling (through the CDS) with the BHA. The frictional heat caused by tool movement may have affected the temperature measurement.

Deployment 2: Hole U1320A, 289.9 mbsf

Table AT5 and FIGUREA3_1320A33.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 1. As the probe was pushed into the formation, the temperature and pressure increased. The pressure then decreased rapidly to less than the hydrostatic pressure. Once again, an internal leak is interpreted to be present; no in situ pressure can be inferred from Deployment 2. The temperature record was reasonable, and the last temperature reading was 11.08°C. The accelerometer recorded tool movements throughout the dissipation phase. The frictional heat caused by tool movement may have affected the temperature measurement.

Deployment 3: Hole U1324B, 229.1 mbsf

Table AT6 and FIGUREA4_1324B27.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 3. The TruView data are missing for this deployment. Key deployment events are derived from the shipboard DVTPP Downhole Tool Data Sheet (see the “DOWNHOLE” folder in “Supplementary material”) and the pressure and temperature data.

When the probe was pushed into the formation, the temperature and pressure increased. After the penetration pressure pulse, the pressure decreased rapidly and erratically. Because of the internal leak, no in situ pressure could be inferred from Deployment 3. The temperature record looks reasonable, and the last temperature reading was 9.5°C. The accelerometer recorded tool movements throughout the dissipation phase. The tool movements resulted in a slight oscillation (magnitude ≈ 0.05°C, period ≈ 1 min) in the temperature record. This most likely was due to some coupling between the BHA and the tool. The frictional heat caused by tool movement may have affected the temperature measurement.

Deployment 4: Hole U1324B, 362.4 mbsf

Table AT7 and FIGUREA5_1324B45.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 4. The TruView data do not match this deployment. Key deployment events are derived from the shipboard DVTPP Downhole Tool Data Sheet (see the “DOWNHOLE” folder in “Supplementary material”) and the pressure and temperature data.

As the pressure decay started, the pressure decreased rapidly and erratically. This was the fourth consecutive deployment where erratic pressures were recorded. After this deployment the tool was inspected and an internal hydraulic leak was found and fixed. No in situ pressure could be inferred from Deployment 4 because of the leak. The temperature record was reasonable, and the last reading was 11.68°C. The temperature record had a very slight oscillation (magnitude ≈ 0.01°C, period ≈ 1 min) during the dissipation phase, whereas the accelerometer did not record significant tool acceleration. This indicates some minor coupling between the BHA and the tool.

Deployment 5: Hole U1324B, 387.9 mbsf

No data were recorded for this deployment.

Deployment 6: Hole U1324B, 464.3 mbsf

Table AT8 and FIGUREA6_1324B59.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 6. The TruView data do not match this deployment. Key deployment events are derived from the shipboard DVTPP Downhole Tool Data Sheet (see the “DOWNHOLE” folder in “Supplementary material”) and the pressure and temperature data.

As the probe was pushed into the formation, the temperature and pressure increased (Table AT8). When the BHA was lifted to decouple the BHA through the CDS, the pressure decreased dramatically to subhydrostatic pressure. A pressure rebound then occurred. We interpret that the tool was pulled up with the BHA, creating a void around the probe tip. As the void equilibrated with the formation, the pressure increased to 14.86 MPa at the end of the deployment. This deployment recorded a good temperature decay curve. The last temperature reading was 12.96°C.

Deployment 7: Hole U1324B, 493.1 mbsf

Table AT9 and FIGUREA7_1324B62.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 7. The TruView data do not match this deployment. Key deployment events are derived from the onboard DVTPP Downhole Tool Data Sheet (see the “DOWNHOLE” folder in “Supplementary material”) and the pressure and temperature profiles.

As the probe was pushed into the formation, the temperature and pressure increased (Table AT9). After penetration, the pressure decreased to a value significantly below hydrostatic pressure and then slowly rebounded to a final value of 12.72 MPa. The pressure data may be explained by either a slow tool pullout after penetration or penetration in a dilatant sediment. Core photos show that the sediment at this location is clayey silt to silt. Probe penetration could generate an annular dilation zone around the probe, which could have significant negative excess pore pressure. The drop to subhydrostatic pressure may reflect this negative excess pore pressure migrating to the pressure port. The temperature record looks very good, and the last temperature reading was 13.4°C.

Deployment 8: Hole U1324B, 521.9 mbsf

Table AT10 and FIGUREA8_1324B64.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 8. The measured pore pressure was less than the hydrostatic pressure throughout the deployment, and there was no record of penetration. As a result, during the next DVTPP deployment, the DVTPP3 was deployed and the DVTPP2 was rebuilt.

The temperature record was reasonable. The last temperature reading was 13.84°C. However, the DVTPP Downhole Tool Data Sheet (see the “DOWNHOLE” folder in “Supplementary material”) documented a tool pullout operation 5 min after the end of the penetration. At this time, the BHA moved upward 4 m and the hookload increased. The BHA then moved upward 2 m and lowered and raised again. All of this occurred during the dissipation phase. The raising and lowering of the BHA were recorded by increases and decreases in the hookload and the accelerometer record. The thermistor did not record any significant temperature change during those operations. A second pullout occurred 41 min after the penetration. These observations suggest that the first “pullout” and the following bit movements were within the retraction/​extension limit of the CDS and thus did not cause significant tool movement.

Deployment 9: Hole U1324B, 541.1 mbsf

A programming error occurred during this deployment and no data were recorded.

Deployment 10: Hole U1324B, 560.4 mbsf

Table AT11 and FIGUREA9_1324B68.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 8. Pressure and temperature both increased sharply during penetration. When the BHA was lifted to decouple the BHA, the pressure decreased rapidly by ~1 MPa and then decayed to a value of 20 MPa while the tool was in the formation. The pressure decayed linearly with time, which was unusual. Additionally, the pressure did not decrease to atmospheric pressure when the DVTPP was raised to the rig floor. In situ pressure may not be inferred from this deployment. The temperature decreased to 15.69°C prior to pullout.

Deployment 11: Hole U1324B, 589.2 mbsf

Table AT12 and FIGUREA10_1324B72.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 11. The temperature and pressure sensors both recorded unreliable data during this deployment.

Deployment 12: U1324B, 608.2 mbsf

Deployment 12 was completed at the base of the hole. Table AT13 and FIGUREA11_1324B74.XLS in the “APP_A” folder in “Supplementary material”present the sequence of operations and the tool response to particular events for this deployment. The pressure increased during penetration and then quickly declined, followed by a rapid recovery. The bit movement and acceleration record suggest that the quick pressure drop was related to the decoupling of the tool from the drill string after the insertion, and the rapid recovery was due to reset of the tool on its own weight. The pressure then followed a dissipation profile to a final pressure of 18.9 MPa. The temperature record continuously decayed to a low value of 17.2°C and then slightly increased to 17.34°C. The last temperature reading was 17.15°C. The accelerometer recorded tool movements throughout the dissipation phase. We interpret a coupling between the BHA and the tool. The oscillating pressure and the odd temperature record were caused by tool movements.

Deployment 13: Hole U1324C, 250 mbsf

Table AT14 and FIGUREA12_1324C05.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 13. Similar to Deployment 12, this deployment also recorded tool movement during the dissipation phase. No sharp pressure drop was recorded when the drill bit was raised after insertion. The temperature record increased slightly during the dissipation phase, and the last temperature reading was 11.01°C. This reading may not reflect the formation temperature due to the influence of the tool movement. The pressure also slightly increased during dissipation and then subsided to an end value of 14.7 MPa. This pressure increase may affect the estimate of the formation pressure.

Deployment 14: Hole U1324C, 405 mbsf

Table AT15 and FIGUREA13_1324C07.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 14. The tool insertion generated a relatively small pressure pulse for this depth. The pressure dropped rapidly when the drill bit was lifted. The pressure then rebounded to a final value of 15.82 MPa, which was very close to the recorded pressure at BOH prior to the penetration. The temperature increased when the drill bit was lifted and then decreased rapidly to a value close to the borehole fluid temperature. Near the end of the deployment, the temperature increased to a final value of 11.38°C. The temperature increase was most likely due to tool movement, which can be identified on the acceleration data. We interpret that tool dislodgement weakened the seal around the probe and created communication with the borehole fluid. The sensors recorded the pressure and temperature of the borehole fluids instead of in situ conditions.

Deployment 15: Hole U1324C, 505 mbsf

Table AT16 and FIGUREA14_1324C08.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 15. Similar to Deployment 14, the tool insertion generated a relatively small pressure pulse for this depth. The pressure decreased rapidly when the drill bit was lifted. The pressure then rebounded to a nearly constant value. The temperature only slightly decreased after penetration and then increased to a high value (higher than its penetration temperature) at the end of the deployment. We interpreted that the tool surface temperature was lower than the formation temperature during penetration. The tool temperature had to increase to equilibrate with the formation. The end temperature was 13.5°C.

Deployment 16: Hole U1322B, 166.7 mbsf

Table AT17 and FIGUREA15_1322B19.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 16. The temperature and pressure increased when the CDS latched in position. This suggests that the tip went into the formation slightly while the CDS was latching in. When the drill bit was lowered to insert the tool, it recorded a second temperature and pressure increase. Pressure decreased rapidly when the drill bit was lifted. The pressure then quickly rebounded to a near-constant value that was very close to the recorded pressure at BOH prior to penetration. There may have been communication with the borehole fluid. The temperature dropped rapidly and then slowly increased to 9.06°C. The end temperature of 9.06°C was not representative of in situ conditions.

Deployment 17: Hole U1322C, 100 mbsf

Table AT18 and FIGUREA16_1322C02.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 17. The bit depth dramatically shifted during this deployment, and the block position data are not available. The pressure decreased rapidly after the insertion spike and then slowly dissipated to a final value of 14.73 MPa. This dissipation curve may be extrapolated to estimate in situ pressure. The temperature record had good insertion spike and continuous decay curve. The last temperature reading was 7.04°C.

Deployment 18: Hole U1322C, 220 mbsf

Table AT19 and FIGUREA17_1322C03.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 18. The pressure increased during penetration and then decreased abruptly when the drill bit was lifted. The pressure then rebounded slowly to a final value of 16.36 MPa. Modeling of the rebound curve may constrain the in situ pressure. The temperature record had good insertion spike and continuous decay curve. The temperature decayed to 9.11°C at the end of deployment.

Deployment 19: Hole U1322C, 238 mbsf

Table AT20 and FIGUREA18_1322C04.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 19. The pressure increased during penetration and decreased abruptly when the bit was picked up off BOH. Pressure then slowly dissipated to a final value of 16.55 MPa. Extrapolation of the pressure record may provide an estimate of the in situ pressure. The temperature record had good insertion spike and continuous decay curve. The temperature decayed to 10.03°C at the end of deployment.

Deployment 20: Hole U1322D, 175 mbsf

Table AT3 and FIGUREA1_1322D04.XLS in the “APP_A” folder in “Supplementary material” present the sequence of operations and the tool response to particular events for DVTPP Deployment 20. Both pressure and temperature profiles had good insertion spikes and continuous decay curves. The pressure dissipated to 16.37 MPa and the temperature dissipated to 8.68°C at the end of the deployment. Extrapolation of the pressure record will provide estimate of the in situ condition.