Subsea Pipeline Shutdown Hydrate Prevention via Gel Segmentation
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Solution Overview
Problem
Existing methods for managing subsea oil production pipes face challenges during shutdowns, particularly at great depths, where temperature drops lead to increased viscosity, precipitation of paraffins and asphaltenes, and formation of gas hydrates, causing blockages and making pipe maintenance difficult and costly.
Innovation Solution
A method involving selective depressurization and replacement of production fluid with an inert fluid, combined with the use of a separation gel to isolate and separate production fluids, preventing hydrate formation and allowing for efficient pipe maintenance without fluid replacement, thereby reducing operational risks and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If production is stopped in deep-sea pipes, then the production process can be maintained or restarted, but the temperature drops cause increased viscosity, paraffin precipitation, and hydrate formation leading to pipe blockages
Solution Approach 1:
The patent applies preliminary action by performing depressurization and fluid replacement before shutdown, and by preparing separation gel barriers in advance. The method proactively manages the transition to shutdown conditions by pre-treating the production fluid and establishing protective barriers (gel sections) that prevent hydrate formation during the shutdown period, rather than reacting to blockages after they occur.
Solution Approach 2:
The patent replaces production fluid with an inert fluid (such as nitrogen or carbon dioxide) that cannot form hydrates under the given conditions. This creates an inert environment in the pipe during shutdown, eliminating the harmful factor of hydrate formation while maintaining pipe pressure and temperature conditions that prevent paraffin precipitation and viscosity increase.
2Object-affected harmful factors
If thermal insulation and heating are used to maintain temperature, then hydrate formation is prevented, but energy consumption increases and cooling delay occurs during shutdown
Solution Approach 1:
The patent changes the fundamental parameter of the fluid in the pipe from production fluid (which forms hydrates) to an inert fluid (which does not form hydrates). This parameter change eliminates the need for thermal insulation and heating to prevent hydrate formation, as the inert fluid inherently resists hydrate formation across a wide temperature and pressure range, significantly reducing energy consumption during shutdown.
Solution Approach 2:
The patent extracts and removes the harmful component (production fluid capable of forming hydrates) from the pipe system during shutdown, replacing it with an inert fluid. This extraction eliminates the root cause of hydrate formation rather than merely managing its symptoms through heating, thereby reducing energy consumption while maintaining protection against blockages.
3Manufacturing precision
If mechanical scrapers are used to clean paraffin and asphaltene deposits, then pipe internal diameter is restored, but operational complexity and maintenance cost increase
Solution Approach 1:
By maintaining an inert fluid environment in the pipe during shutdown, the patent prevents the conditions that lead to paraffin and asphaltene precipitation and deposition. The inert fluid stabilizes the production fluid properties and prevents harmful phase separations, thereby eliminating the need for mechanical scraping operations and reducing maintenance complexity.
Solution Approach 2:
The patent converts the potential harm of shutdown (which would normally cause deposits) into a beneficial opportunity to flush the pipe with inert fluid that prevents deposition. The shutdown period, which traditionally requires costly mechanical cleaning, becomes a time when the inert fluid actively protects the pipe interior, transforming a harmful situation into a protective one and eliminating the need for complex scraper operations.
4Object-affected harmful factors
If the entire production line is depressurized to prevent hydrates, then hydrate formation is avoided, but production restart becomes difficult due to fluid column weight and pressure recovery issues
Solution Approach 1:
The patent segments the pipe system into sections separated by gel barriers. The separation gel creates distinct zones that allow selective pressure management - the upper section can be depressurized to prevent hydrates while the lower section near the wellhead maintains production pressure. This segmentation enables controlled restart by progressively repressurizing sections rather than requiring complete system pressurization, easing operational difficulty.
Solution Approach 2:
The separation gel acts as an intermediary substance between the inert fluid and any remaining production fluid or gas. This gel barrier allows pressure differentials to exist across it, enabling the upper pipe section to be depressurized while maintaining pressure in the lower section. The gel mediator facilitates controlled pressure management and simplifies restart operations by allowing gradual pressure equalization without causing hydrate formation.
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 effectively prevents hydrate formation and maintains pipe integrity during shutdowns and restarts, reducing the need for extensive fluid replacement and mechanical scrapers, thus saving time and resources while ensuring safe and efficient production resumption.
Implementation Method 1
introduction of a separation gel into said first pipe section, said separation gel forming a section of gel pushing said cold production fluid contained in said first pipe section towards said second pipe section
Implementation Method 2
said hot production fluid behind said section of gel heating said degassed cold production fluid contained in said first pipe section in front of said section of gel, thereby raising its temperature above a temperature point below which hydrates form
Data Source
Figure 1
Figure 1A
Figure 1B
AI summary
The invention relates to a method for shutting down production and securing a subsea production pipeline (1) comprising a first pipeline section (1-1) resting on the seabed (16) from a wellhead (17) to the lower end (1-2a) of a second pipeline section (1-2) rising to a vessel or floating support (10) on the surface, wherein after the shutdown of production, a first depressurization of the entire subsea production pipeline (1) is carried out by allowing only a portion of the gas contained in the production fluid contained in said production pipeline (1) to escape to the surface through its upper end (1-2b), characterized in that the following steps are then carried out, in which: a) said first production pipeline section (1-1) is isolated from said second pipeline section (1-2),and the production fluid is left in the said first part of the production line (1-1), and not in the said second part of the line (1-2) which is drained, and b) a further depressurization is carried out of the first part of the production line (1-1) filled with production fluid, by reducing the pressure in the said first part of the line (1-1) and by more completely evacuating the gas contained in the production fluid it contains.