Flexible Pipe Annulus Drainage for CO2 Pressure Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pre-salt oil reservoirs with high CO2 content lead to CO2 stress corrosion cracking in flexible offshore pipelines due to gas permeation and water condensation in the annular space, causing pressure buildup and potential rupture, which poses risks to operational continuity and safety.
Innovation Solution
A system and method using a ROV with a cylinder and plunger assembly, anti-collapse hose, and vacuum pump to reduce annulus pressure to atmospheric levels, eliminating condensed water and reducing CO2 partial pressure, thereby mitigating corrosion and facilitating safer and faster pipe collection operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the annular space is left sealed with permeated gases and water vapor, then the tightness and containment of the pipe are maintained, but pressure build-up occurs leading to CO2 stress corrosion cracking and potential rupture
Solution Approach 1:
The patent extracts harmful substances (gases and water vapor) from the annular space through a drainage system. The system includes a drainage conduit connected to the annular space that allows removal of permeated gases and condensed water, thereby eliminating the source of CO2 stress corrosion while maintaining pipe integrity
Solution Approach 2:
The patent introduces an intermediary substance (inert gas or liquid) to displace harmful gases from the annular space. This intermediary fills the annular space after drainage, creating a protective atmosphere that prevents CO2 corrosion while maintaining pressure balance
2Productivity
If the collection speed is increased during pipe operations, then productivity is improved, but the risk of outer cap explosion increases due to pressure build-up in the annulus
Solution Approach 1:
The patent performs preliminary drainage of the annular space before pipe collection operations. By removing gases and water vapor in advance, the system prevents pressure build-up during subsequent high-speed collection operations, enabling faster productivity without compromising outer cap integrity
3Ease of manufacture
If water vapor permeation is allowed through the polymeric barrier, then the natural permeation process occurs, but water condensation builds up in the annulus causing pressure increase
Solution Approach 1:
The patent extracts condensed water from the annular space through the drainage system. The drainage conduit removes accumulated water vapor condensation, preventing pressure build-up while allowing the polymeric barrier to maintain its natural permeation functionality
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 solution effectively reduces the risk of corrosion and rupture, enabling continuous operation of pre-salt pipes by maintaining low annulus pressure, reducing collection time, and minimizing exposure to harmful gases during pipe handling.
Implementation Method 1
The invention further provides for the application of vacuum in the annular space, in order to drain the water that may be present therein
Implementation Method 2
The system consists of a cylinder and plunger assembly that is installed in the recess where the relief valve of the flexible pipe connector is present
Implementation Method 3
The presence of water in the annular space can also occur by the condensation of permeated water vapor. This occurs when the fluid produced contains water. The water vapor permeates through the polymeric barrier of internal sealing of the pipe
Implementation Method 4
In this type of pipe, part of the produced gases permeates through the polymeric layer of internal sealing of the flexible pipe until they reach the metallic layers
Data Source
AI summary
The invention presents a system and method for reducing pressure and draining the annulus of submerged flexible pipes, with application in all flexible pipe structures and in any industry that uses these types of pipes. Its objectives are to eliminate condensed water and reduce the partial pressure of CO2, thus restoring the integrity of the pipes. In addition, with the reduction of the pressure of the annulus gases, the operations of collection of the pipes can be carried out with greater speed, that is, in less time. The previous relief of the annulus pressure further reduces the risk of rupture of the outer cap during the operation, thus reducing the risk of exposing operators to the presence of harmful gases, when the pipe reaches the deck of the PLSV vessel.