Riser Slug Control via Gas-Liquid Cyclone Separation
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Solution Overview
Problem
Existing systems for controlling slugging in offshore risers, particularly severe slugging, are inefficient and costly, often requiring impractical separator size increases, increased backpressure, or additional energy, which can lead to production losses and equipment damage due to large flow rate and pressure fluctuations.
Innovation Solution
A riser-based slug control system utilizing a gas-liquid separator, such as a gas-liquid cylindrical cyclone (GLCC), that separates production fluid into gas and liquid phases and recombines them to create a homogeneous mixture, allowing unobstructed gas flow and reducing the likelihood of severe slugging by using the gas to lift the liquid efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional slugging control methods are used (increasing separator size, increasing backpressure, or adding energy), then slugging can be controlled, but production losses and equipment damage occur due to large flow rate and pressure fluctuations
Solution Approach 1:
The liquid level sensor detects liquid accumulation in the riser before severe slugging occurs. The control system activates the submersible pump in advance to remove the liquid, preventing the blockage from developing into severe slugging. This preliminary intervention maintains production flow while avoiding the large pressure fluctuations that cause equipment damage and production losses.
Solution Approach 2:
The system uses the production fluid's own liquid phase as the control agent. When liquid accumulates in the riser, the sensor detects this and triggers the pump to remove the liquid, using the system's own components rather than requiring external control systems. This self-regulating approach maintains reliability while minimizing production disruption.
2Reliability
If separator size is increased to handle slugs, then slugging control is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts the slugging control function from the separator and relocates it to the riser. The liquid level sensor and submersible pump are installed directly in the riser, separating the slug detection and removal functions from the separator. This allows the separator to remain compact while achieving effective slugging control through the distributed control system in the riser.
3Reliability
If backpressure is increased to control slugging, then slugging control is improved, but production losses occur
Solution Approach 1:
The system uses hydraulic principles by installing a submersible pump in the liquid-filled riser to actively remove accumulated liquid. This hydraulic control method replaces the pneumatic approach of increasing backpressure, allowing liquid removal without creating the large pressure fluctuations that would reduce production flow and cause equipment damage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively prevents liquid blockages, maintains a uniform flow rate and pressure, and delays the need for external energy sources, reducing the occurrence of severe slugging and enhancing the efficiency of fluid transport through the riser.
Implementation Method 1
separates the production fluid into a gas phase and a liquid phase... with the liquid from the production fluid collecting in a lower portion of the volume and the gas from the production fluid collecting in an upper portion of the volume
Implementation Method 2
The pressure drop from gas flowing through the orifices in the upper section creates a low pressure in the tubular passage which draws liquid from the lower portion
Implementation Method 3
allowing unobstructed gas flow and reducing the likelihood of severe slugging by using the gas to lift the liquid efficiently
Data Source
AI summary
A riser-based slug control system and a method of controlling slugging in a fluid flowing through a riser are provided. The system includes a gas-liquid separation separator that has a housing defining an internal volume. An inclined inlet is connected to the housing and configured to receive a flow of multiphase fluid and direct the flow of fluid into the housing so that the fluid flows spirally in the volume and separates, with gas from the fluid collecting in an upper portion of the volume and liquid from the fluid collecting in a lower portion of the volume. A tubular passage, which extends at least partially through the internal volume of the housing, defines a plurality of orifices. The tubular passage is configured to receive liquid from the lower portion of the volume and gas from upper portion of the volume, and deliver the mixture of the combined liquid and gas through an outlet.