Monitoring Liquid Slugs Using Distributed Acoustic Sensing and an Air Gun

Area of Science:

• Geophysics
• Petroleum Engineering
• Sensing Technology

Background:

• Distributed acoustic sensing (DAS) uses fiber optic cables to detect acoustic signals.
• Liquid slugs in vertical wells can complicate well monitoring and flow management.
• Existing methods relying on flow-induced noise may lack sufficient signal strength for reliable slug detection.

Purpose of the Study:

• To evaluate the effectiveness of DAS stimulated with acoustic pulses for real-time liquid slug tracking.
• To compare acoustic pulse-stimulated DAS with passive noise monitoring for slug detection.
• To estimate slug parameters like velocity, location, and body length using DAS.

Main Methods:

• Induced liquid slugs in a 427 m vertical test well using surface-controlled gas lift valves.
• Applied acoustic pulses via a fluid level gun to enhance DAS monitoring.
• Analyzed backscattered light from DAS signals using frequency band energy plots and phase shift measurements.

Main Results:

• DAS successfully tracked liquid slug movement in real-time.
• Acoustic pulse stimulation significantly improved signal strength for slug detection compared to flow-induced noise alone.
• Estimated slug velocity, location, and body length with the enhanced DAS method.

Conclusions:

• DAS stimulated with acoustic pulses is a viable technique for real-time liquid slug detection and characterization.
• This approach offers improved well monitoring and flow management capabilities.
• Acoustic pulse stimulation overcomes limitations of relying solely on ambient noise in multiphase flows.