What are the best practices for correcting environmental effects on well logs?

3 Adjust for mud properties

The mud properties, such as density, viscosity, salinity, and resistivity, can also affect the well log measurements, especially for resistivity, sonic, and nuclear logs. Mud properties can vary due to drilling operations, formation interactions, and contamination. Therefore, it is important to monitor and adjust for mud properties using mud logs, samples, and sensors, and to apply suitable mud corrections to the well logs. Mud corrections can be done using charts, tables, or equations, depending on the mud type and the logging tool.

4 Compensate for tool response

The tool response is another factor that can influence the well log quality. Tool response refers to the physical characteristics and limitations of the logging tool, such as geometry, configuration, depth of investigation, and vertical resolution. Tool response can cause errors and uncertainties in the log measurements, such as shoulder effects, borehole effects, dispersion effects, and multiple reflections. Therefore, it is necessary to compensate for tool response using correction curves, deconvolution techniques, or modeling methods, depending on the tool design and the log type.

5 Validate the log data

The final step in correcting environmental effects on well logs is to validate the log data. Validation is the process of checking and verifying the log data for quality, consistency, and accuracy. Validation can be done using various methods, such as crossplots, overlays, statistical analysis, and comparison with core data, test data, or other logs. Validation helps to identify and eliminate any remaining errors or anomalies in the log data, and to confirm or revise the correction methods applied.

By following these best practices, drilling engineers can correct environmental effects on well logs and improve their interpretation and analysis. Correcting environmental effects on well logs can enhance the understanding of the formation properties and the well performance, and enable better decision making and optimization for drilling operations.