903 Well Site Completion and Servicing Safety

Well Logging

Well logging is the process of collecting and recording information about subsurface geologic formations encountered during drilling. These records help describe the physical and chemical characteristics of the rocks and fluids beneath the surface. Well logs may include information recorded by the driller, mud and cuttings analyses, core analyses, drill stem test results, and measurements obtained through electric, acoustic, and radioactivity-based logging procedures.

The primary purpose of well logging is to identify the characteristics of formations surrounding the wellbore. Logging data helps determine rock type, formation thickness, porosity, permeability, fluid content, formation pressure, and other downhole properties. This information is used to evaluate the potential for oil, gas, groundwater, or other resources, as well as to support decisions about well completion and production.

Well logging may be performed while drilling (logging-while-drilling or LWD) or after drilling operations have paused or been completed using wireline logging tools. The type of logging method selected depends on the information needed and the stage of the drilling operation.

Well logging tools include a variety of specialized instruments designed to measure specific formation properties. Common tools include:

• Radioactive tools that measure natural or induced radiation to estimate formation density and porosity.
• Electric tools that measure electrical resistivity and conductivity to help identify rock types and the presence of hydrocarbons or water.
• Mechanical tools that measure wellbore diameter, formation dip, or other physical characteristics.
• Sonic (acoustic) tools that measure the travel time of sound waves through formations to evaluate rock properties, porosity, and well integrity.
• Temperature and pressure tools that monitor downhole conditions to help evaluate reservoir performance and well conditions.

Because some logging operations use radioactive sources or high-voltage electrical equipment, they present unique hazards. Workers involved in well logging should follow established safety procedures, maintain effective communication with the drilling crew, use appropriate personal protective equipment (PPE), and follow site-specific controls for handling, transporting, and securing logging equipment and radioactive sources.

Potential Hazards

• being exposed to radiation
• getting injured due to an unexpected release of pressure

Possible Solutions

• Keep non-essential workers away from the rig floor and marked-off areas where radiation hazards may be present.
• Wear appropriate personal protective equipment (PPE).
• Allow only authorized and qualified logging company personnel to handle the logging tools.
• Report any damage to radioactive logging tools.
• Check for the presence of trapped pressure before opening the tool housing.

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