Subsea Riser-Less Plug and Abandonment Fluid Control
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Solution Overview
Problem
Conventional subsea well plug and abandonment methods relying on drilling rigs are expensive and time-consuming, and lack of marine risers complicates fluid volume control during vessel-based operations.
Innovation Solution
A riser-less method and apparatus for controlling fluid volume in subsea wellbore systems, utilizing a wellhead interface module, subsea flow control package, and system control module to monitor and manage fluid levels and flow, allowing for vessel-based operations without a marine riser system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drilling rigs are used for subsea well plug and abandonment operations, then full fluid volume control and wellbore re-filling capability are achieved, but operational costs and time consumption increase significantly
Solution Approach 1:
The invention extracts the essential fluid control functions from the complex drilling rig system and implements them independently using a subsea flow control package with pump and valve, eliminating the need for expensive drilling rig deployment while maintaining full volume control capability
Solution Approach 2:
A marine hose serves as an intermediary fluid conduit between the vessel and subsea wellhead, enabling fluid transfer and volume control operations without requiring a rigid marine riser system, thus reducing operational complexity and cost
2Ease of operation
If marine riser system is installed for vessel-based operations, then fluid flow control is simplified, but device complexity and installation time increase
Solution Approach 1:
The invention removes the marine riser component from the system entirely and replaces it with a flexible hose connection, extracting only the essential fluid conduit function while eliminating the complex rigid riser structure and its associated installation requirements
Solution Approach 2:
The system transitions from a rigid, fixed-geometry marine riser to a flexible hose with variable configuration, allowing the fluid conduit to adapt to different operational positions and wellhead locations while maintaining flow control capability
3Reliability
If drilling rig is deployed for plug and abandonment, then comprehensive wellbore control is achieved, but mobilization time and cost increase
Solution Approach 1:
The invention extracts the critical wellbore control functions from the drilling rig platform and implements them through a compact subsea flow control package that can be deployed independently, eliminating the lengthy drilling rig mobilization process while maintaining comprehensive wellbore control capability
Solution Approach 2:
The subsea flow control package is designed to be self-contained with integrated pump, valve, and control systems that can operate autonomously from the vessel, eliminating the need for external drilling rig support services and reducing overall operational time
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
Enables efficient and cost-effective plug and abandonment operations by providing full volume control and re-filling of the wellbore fluid, characterizing wellbore conditions, and managing fluid influx or loss, thus reducing operational costs and time.
Implementation Method 1
The subsea flow control package defines a first flow path between wellhead interface module and the fluid conduit via a pump
Implementation Method 2
The subsea flow control package defines a second flow path between the wellhead interface module and the fluid conduit via a flow control valve
Implementation Method 3
measuring, using a level sensor of the wellhead interface module, a level of the wellbore fluid in the chamber
Data Source
Figure 1
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Figure 3
AI summary
The invention provides a method and apparatus for performing a plug and abandonment operation on a subsea well. A wellhead interface module (20) is located on a wellhead (13), which accommodates a volume of wellbore fluid in fluid communication with the wellbore. A system control module (80) receives a signal from a sensor (27) in a chamber (23) of said wellhead interface module and is configured to derive volume data relating to a change in volume of wellbore fluid in the chamber and compares the derived volume data with a volume change expected due to the removal of tubing from the wellbore. In embodiments of the invention, this enables a change in wellbore conditions to be characterised, for example a fluid influx or a fluid loss, from the volume data. The method may comprise providing wellbore fluid to the chamber by means of a flow control package (40) to replace fluid which enters the wellbore to occupy the volume vacated by the tubing, and/or removing or adding fluid in fluid influx/ loss situations respectively.