Helical Flowpath for Oil-Water Separation
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Solution Overview
Problem
Conventional methods for purifying water produced from subterranean oil and gas wells, such as settling tanks and hydrocyclones, are inefficient and costly, particularly when dealing with high flow rates and the need for low oil and sand content to prevent well plugging and meet reinjection standards.
Innovation Solution
A method and apparatus utilizing a helical flowpath to separate multiphase fluid streams by elevating the critical Reynolds number, allowing for increased fluid velocity while maintaining a non-turbulent flow regime, which enhances the separation of lighter and heavier fluid components through centrifugal forces and subsequent vortex separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If settling tanks are used for oil-water separation, then separation of oil from water can be achieved, but the vessel requires large volume and long residence time, making it costly and unsuitable for subsea locations
Solution Approach 1:
The patent replaces the conventional gravity-based settling mechanism with a centrifugal separation mechanism. The helical flowpath generates centrifugal forces that act on the oil-water mixture, separating the phases based on density differences. This mechanical substitution allows for much shorter residence times and smaller equipment volumes while achieving the same or better separation efficiency.
Solution Approach 2:
The patent employs a helical (curved) flowpath instead of a straight or horizontal settling configuration. The curved geometry generates centrifugal forces during fluid flow, creating radial acceleration that enhances phase separation. This curvature-based approach transforms the separation mechanism from simple gravity settling to centrifugal separation, dramatically reducing the required vessel volume.
2Reliability
If hydrocyclones are used for de-oiling, then high separation efficiency is achieved, but the devices are effective only at low liquid flow rates, limiting throughput to approximately 1200 barrels per day
Solution Approach 1:
The patent employs a dynamic flowpath configuration where the helical geometry and flow conditions can be optimized for different throughput levels. The system maintains effective centrifugal separation across a wide range of flow rates by adjusting operational parameters such as inlet pressure and flow distribution, allowing the same device to handle both low and high throughput scenarios while maintaining separation efficiency.
Solution Approach 2:
The patent divides the fluid stream into multiple parallel flowpaths or uses multiple helical separation zones within the same vessel. This segmentation allows the total throughput to be distributed across several channels, each operating at optimal flow rates for effective separation. The segmented approach enables the system to handle high total throughput while maintaining the separation efficiency characteristic of lower flow rate operation.
3Reliability
If conventional settling tanks are used, then oil-water separation occurs under gravity, but the separation efficiency is low and requires excessively long residence times
Solution Approach 1:
The patent introduces preliminary centrifugal action through the helical flowpath configuration before the fluid reaches the separation zone. The curved inlet and flowpath pre-condition the oil-water mixture by initiating phase separation through centrifugal forces, so that when the fluid enters the main separation region, the separation process is already well underway. This preliminary action significantly reduces the residence time required to achieve target separation efficiency.
Solution Approach 2:
The patent replaces passive gravity settling with active centrifugal separation. Instead of relying solely on gravitational force acting vertically on the oil-water mixture, the system uses the kinetic energy of the flowing fluid and the helical flowpath geometry to generate centrifugal forces. This mechanical substitution creates much stronger separation forces, reducing the time required for phases to separate by an order of magnitude or more.
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
This approach enables high-efficiency separation of oil from water over a wide range of flow rates, allowing for the production of water suitable for reinjection with low oil content, even in challenging subsea environments, and can be modularly scaled to accommodate varying flow rates.
Implementation Method 1
causing the fluid to flow along a helical flowpath in which the critical Reynolds number of the fluid flow is elevated, the fluid stream flowing at a Reynolds number below the elevated critical number, the fluid stream flowing at a sufficient velocity to cause the fluid phases to separate
Implementation Method 2
A method and apparatus utilizing a helical flowpath to separate multiphase fluid streams by elevating the critical Reynolds number, allowing for increased fluid velocity while maintaining a non-turbulent flow regime
Data Source
AI summary
A method and apparatus are disclosed for separating a multiphase fluid stream that includes a heavier fluid component and a lighter fluid component. The fluid flows along a first helical flowpath with a first pitch. The first helical flowpath is sufficiently long to establish a stabilised rotating fluid flow pattern for the stream. The uniform rotating fluid also flows along a second helical flowpath, the second helical flowpath having a second pitch greater than the first pitch. The lighter fluid is removed from a radially inner region of the second helical flowpath. The method and apparatus are particularly suitable for the separation of oil droplets from water, especially from water for reinjection into a subterranean formation as part of an oil and gas production operation. The method and apparatus are conveniently applied on a modular basis.