Ultra-High Temperature Multi-Sensor Memory Tool (UHT-MSM)


The Ultra-High Temperature Multi-Sensor Memory Tool (UHT-MSM), developed by the Geophysical Research Corporation for the University of Miami under NSF funding, is a slim-hole memory tool capable of measuring pressure and temperature in hot boreholes. It was deployed for the first time during ODP Leg 169. The UHT-MSM contains internal and external temperature measuring devices, a pressure gauge, a multi-sensor memory unit, and a dewar flask that acts as an insulator to maintain a stable temperature and cool-down rate for the tool. The heat shield is aircraft-grade aluminum bound at both ends by brass heat sinks. The dewar flask can maintain an internal temperature suitable for tool operation for 4-5 hours at an external temperature of about 750° F (400° C). Operations are possible for up to 10 hours if the temperature does not exceed 450° F (232° C).




Hydrogeology. It is used to identify regions of fluid inflow or outflow.

Geothermics. Provides an estimate of the vertical fluid flow regime.

Safety. It provides an evaluation of fluid temperature prior to deploying heat sensitive tools.

Environmental Effects

Tool response can be affected by borehole size and circulation of fluids during drilling operations. Down flow of colder and denser ocean bottom water after drilling into the borehole can affect the temperature profiles.

Log Presentation


Tool Specifications

Temperature rating: 750° F (400° C) for 4-5 hours 
Pressure rating: 10 kpsi (69 MPa)
Diameter: 2.2 in (5.58 cm)
Length: 8.75 ft (2.66m)
Weight: 75 lbs (34.1 kg)
Sampling Rate: From 20 msec to 65 days
Memory: 1 Mb
Power source: Lithium batteries
Battery life: >8 hrs

Measurement Specifications 

    Range: 32-932° F (500° C)
    Resolution: 15.6 Hz/° F (28 Hz/° C)
    Accuracy: 3° F (1.67° C)
    Range: 0-10 kpsi (0-69 MPa)
    Accuracy: <0.01 psi (68.94 Pa)
    Resolution: 0.04 % of full scale