Why mud monitors are essential for radiation safety during logging while drilling operations?

In the oil and gas industry, radiation-based well logging technologies play a critical role in understanding subsurface formations. During Logging While Drilling (LWD) operations, sealed radioactive sources and neutron generators are often embedded in the drill string to deliver real-time formation data on density, porosity, and lithology.

However, these radioactive sources are exposed to mechanical stress and downhole conditions that can compromise their structural integrity. When a breach occurs, there is a risk that radioactive material may leak into the drilling mud, creating a significant radiation safety concern for rig personnel.

Limitations of standard LWD tools

While the LWD system may continue to transmit data to surface, it typically lacks any built-in capability to detect radiation leaks. If a source is damaged or its containment is breached, the system won’t alert the site team. As a result, contaminated drilling mud may continue circulating through surface systems without detection, leaving personnel unaware of the potential exposure.

This is particularly concerning during operations such as fishing, where the retrieval of stuck tools can involve high mechanical force. If a radioactive source is embedded in the tool being retrieved, there is a heightened risk of housing damage and radiation release.

Addressing the safety gap with mud monitors

To overcome this risk, many operators are turning to mud monitors as a dependable, independent method for radiation monitoring. Installed on the mud return line and mud tank, these systems offer real-time detection of gamma radiation in circulating drilling mud.

Unlike downhole tools, mud monitors are not affected by source failure or communication issues. They provide constant surveillance at surface level, ensuring any radiation event is detected immediately and helping protect rig personnel from undetected exposure.

How the mud monitor system works

The mud monitor system uses Geiger-Müller (GM) tubes to continuously measure radiation levels. Installed in pairs, the system sends a calibrated 4–20 mA output signal (with a background of 10 µSv/h) that can be connected to the rig’s control system or a stand-alone alarm. If radiation levels rise above set thresholds, alarms trigger instantly.

The system also supports WITS communication protocols, making it suitable for remote oversight and centralised monitoring. It is portable, easy to install, and ideal for relocation between rigs, enhancing flexibility across multiple LWD operations.

Industry practice and operational considerations

The installation of mud monitors is now widely recognised as best practice and is increasingly being adopted by leading drilling companies. Many consider it a standard safety requirement wherever radioactive sources are deployed.

Key operational points include:

• Ensuring monitor selection is based on the type and activity of the radioactive source
• Seamless integration into existing wellsite control systems
• Compatibility with 4–20 mA analogue signals and WITS protocols
• Following industry guidelines for the number of monitors per rig, in line with principles used for allocating portable radiation survey meters

Conclusion

Mud monitors are a critical component of modern radiation safety management during LWD operations. They provide an independent layer of protection to:

• Safeguard personnel
• Maintain operational integrity
• Ensure compliance with international radiation protection standards

For any site where radioactive sources are used, mud monitors should be regarded as an essential part of the safety system.

Want to learn more about how our mud monitors improve radiation safety during logging while drilling (LWD) operations? Download our fact sheet.

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