Modular Downhole Tractor (MDT)

The Sondex Downhole Tractor (MDT) is a modular system that is used to transport passenger logging tools into difficult to access areas of the well when standard wireline deployment is not possible.

Description

The MDT is a wireline deployed system used to push passenger logging tools into difficult well profiles. It is modular enabling a number of sections – actuator and drive arms/wheels – to be connected together below the MDT electronics section to provide greater forces to push the tools along the well. The electronics cartridge for the MDT contains a highly efficient (97%) electric motor that controls the clutch and motor assembly of the tool; it also houses tool telemetry boards. Signals from the MDT and associated sensors are compressed downhole in the electronics cartridge for transmitting to surface enabling the logging engineer to monitor various tractor functions in real-time. There is also a surface-controlled switch mechanism, within the electronics cartridge, that isolates the tractor from its passenger tools during the logging survey.

The drive arm and wheels of the actuator section are optimized to provide the maximum tractor force to drive the MDT/logging tool combination along the well. They open when power is applied to the clutch and close when it is switched off. There is a fail-safe mechanism that automatically disengages the clutch if power is lost - completely closing the drive arms – enabling the tractor to be retrieved back to surface. The arms are available in different sizes to match the casing internal diameter; in complex completions each pair of arms can be of different lengths to suit different casing sizes. Each tool is temperature tested and qualified on a test track whilst pulling a heavy load.

Low friction four arm centralisers and knuckle joints specifically designed to operate with the MDT can be included in the tool configuration to aid access in difficult areas of the well. CCL and head tension readings are available with the MDT they are used for depth control and over-pull indication respectively.

WEST software can be use to plan MDT operations in high deviation or horizontal wells. The software can be used to identify many operational considerations such as optimum MDT configuration, the depth at which the MDT should be activated and to plot tractor and cable tension forces. WEST is designed to be used both as part of the pre-job planning and with real-time data acquisition during the logging operation.

Features

• Helicopter transportable.
• Low cost alternative to coil tubing deployment.
• Integrated CCL, head tension, tractor load, speed and position of arms.
• DC powered tractor drives both uphole and downhole.
• Modular drive sections.
• WEST simulation software assists pre-job planning.