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Downhole logging tools

FMS/Sonic Tool String

General Purpose Inclinometry Tool (GPIT*)


The GPIT* General-Purpose Inclinometry Tool provides inclinometer measurements. Tool orientation is defined by three parameters: tool deviation, tool azimuth, and relative bearing. The GPIT tool uses both a three-axis inclinometer and a three-axis magnetometer to make measurements for determining these parameters.

The basic principle of downhole inclinometer measurements is to define accurately the tool system axis with respect to the Earth's gravity (G) and magnetic field (F). Because both vectors are well defined within the Earth system, a relation can be established between the tool and Earth systems. The magnetometer determines Fx, Fy, and Fz, and the inclinometer determines Ax, Ay, and Az for the acceleration due to G. The MAXIS Multitask Acquisition and Imaging System computes deviation, azimuth, and relative bearing from these values


Borehole azimuth, deviation and relative bearing
Orientation of UBI images
Paleomagnetic studies

GPIT data can be used for paleomagnetic studies of oceanic basement. In highly magnetized formations the three-axis magnetometer records the magnetic anomalies caused by the magnetization of the rocks surrounding the borehole.

Environmental Effects

When the GPIT tool is used in an open wellbore, the tools above and below it must have nonmagnetic housings. In a cased hole the tool can be used only for deviation and relative bearing measurements.

Tool Specifications

Temperature rating: 350° F (177° C)
Pressure rating: 20 kpsi (13.8 kPa)
Diameter: 3.625 in (9.2 cm)
Length: 4 ft (1.22 m)
Weight: 55 lbs (25 kg)

Measurement Specifications

Logging speed: 3600 ft/hr
Range of measurement: 0° - 360°
Vertical resolution: 6 in (15.24 cm)
  Azimuth: ±2%
  Deviation: ±2%

Major Outputs

FX: Magnetic field on X Axis (oersted)
FY: Magnetic field on Y Axis (oersted)
FZ: Magnetic field on Z Axis (oersted)
FINC: Magnetic field inclination (degrees)
FNOR: Magnetic field total moment (oersted)
AX: Acceleration X Axis (ft/s2)
AY: Acceleration Y Axis (ft/s2)
AZ: Acceleration Z Axis (ft/s2)

Deployment Notes

The GPIT is typically run with the DSI, FMS, HNGS and UBI.

* ®trademark of Schlumberger