Device To Control Liquid Slugs

The development of deepwater and marginal fields requires accurate hydraulic and mechanical prediction of the pipeline/riser system to ensure the optimum sizing of pipework and associated topsides equipment.  An essential element is the accurate prediction of slug characteristics as this often determines pipe and process equipment design.

BHR was engaged to look at the feasibility of a limited number of concepts to detect and control the speed of slugs of liquids in multiphase pipelines.  The work covered both establishing the market need and potential as well as building and testing an early prototype of the device.

Project Goals

• Determine the functional requirements of the conceptual device (eg pipeline configurations, flow, fluids and pressure operating environment, speed of response, accuracy, etc) by talking to both equipment vendors and pipeline operators (users)
• Decide which type of detection (eg photoelectric, capacitance, pressure, acoustic, ultrasonic, etc) and control processes to use – the prototype comprised a flow splitting device that could alter the size and speed of ‘problem’ slugs
• Build an early prototype of the system using where possible off-the-shelf components (sensors, control equipment, monitoring and analysis components).
• Adapt a two-phase (air/water) flowloop suitable to test the device over a range of operating conditions and slug regimes
• measure the characteristics of the slugs (velocity, length, frequency, holdup) generated in the flowloop over a range of gas and liquid superficial velocities
• Benchmark the performance of the device by determining how well the detection device both measured these slugs and controlled their length if they were considered problematic (a doppler acoustic device was chosen for detection)
• Present the result to the customer ahead of deciding how to proceed onto the next product development stage.

Applications

• On-line measurement and control of slug flow regime upstream of offshore and onshore process facilities
• The slug control system will support the installation of minimum process facilities making remote or marginal field developments more economically viable
• The system comprises a non-intrusive detector that can be retro fitted and used to perform flow regime diagnostics on multiphase pipelines and so is a decision support tool for determining production performance.