An alternative method for sourceless density measurement with boron sleeve gamma detectors

Area of Science:

• Geophysics
• Nuclear Well Logging

Background:

• Neutron Gamma Density (NGD) logging is crucial for formation evaluation.
• The dual gamma detector (NGD-GD) method offers advantages but is sensitive to formation water salinity.
• Existing methods struggle with accuracy in high-brine environments.

Purpose of the Study:

• To address the limitations of NGD-GD in high-salinity formations.
• To develop an improved NGD method resilient to salinity variations.
• To enhance density measurement accuracy and precision in challenging wellbore conditions.

Main Methods:

• Investigated the influence mechanism of formation water salinity on NGD-GD.
• Designed a specialized boron sleeve gamma detector to capture boron-10 capture gamma rays.
• Developed a new NGD method (NGD-BD) utilizing pure boron-10 gamma information for density calculation.

Main Results:

• The NGD-BD method shows improved performance in high-brine, oil, and gas formations compared to NGD-GD.
• NGD-BD offers better density accuracy, precision, and environmental impact than NGD methods using hydrogen capture gamma information.
• A slight decrease in density accuracy and precision was observed compared to NGD-GD in low-salinity conditions.

Conclusions:

• The NGD-BD method is a promising, low-cost alternative to NGD-GD, especially for high-salinity formations.
• This method can be easily integrated with existing NGD tools, improving overall logging quality.
• NGD-BD enhances the reliability of density measurements in diverse geological settings.