Telescopic Riser Closure for Offshore Drilling Pressure Control
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Solution Overview
Problem
Existing drilling systems for offshore drilling struggle to maintain constant fluid pressure in the riser annulus during drilling, especially when the rig moves with tidal and wave movements, which can cause pressure spikes and make it difficult to contain fluid pressure while the drill string is rotating.
Innovation Solution
A drilling system with a telescopic joint and a riser closure device above the slip joint, including a damper system with a pressure regulator and flow control system, which allows for maintaining fluid pressure and controlling fluid flow to manage pressure spikes and rotation of the drill string.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional riser assembly with diverter is used, then fluid pressure can be contained when drilling is stopped, but fluid pressure cannot be contained whilst the drill string is rotating
Solution Approach 1:
The riser assembly is divided into functional segments: a telescopic joint section for length adjustment, a closure device section for pressure containment, and a diverter section for kick management. This segmentation allows each component to perform its specific function independently, enabling pressure containment during rotation while maintaining the ability to respond to kicks.
Solution Approach 2:
A closure device is introduced as an intermediary component between the drill string and the riser annulus. This closure device can seal against the drill string when rotation needs to be stopped for pressure containment, while allowing rotation to continue when drilling operations are active, thus mediating between the conflicting requirements of continuous operation and pressure containment.
2Adaptability or versatility
If the rig moves with tidal and wave movements, then the riser can accommodate movement through telescopic joint, but pressure spikes occur in the riser annulus
Solution Approach 1:
A damper system is installed in the riser annulus to provide beforehand cushioning against pressure spikes. The damper absorbs pressure fluctuations caused by rig movement through the telescopic joint, preventing these fluctuations from propagating as harmful pressure spikes through the drilling system, thus protecting the system while maintaining movement accommodation capability.
3Reliability
If a riser closure device is positioned below the telescopic joint, then pressure containment is achieved, but installation and maintenance become complex
Solution Approach 1:
The riser assembly is segmented with the closure device positioned in a specific section above the telescopic joint, separating the pressure containment function from the movement accommodation function. This segmentation allows the closure device to be installed and maintained independently of the telescopic joint mechanism, simplifying both installation procedures and maintenance operations while maintaining effective pressure containment.
4Productivity
If managed pressure drilling or mud cap drilling is implemented, then drilling efficiency improves, but the system requires complex pressure control capabilities
Solution Approach 1:
The riser assembly integrates multiple functions into a unified system: the telescopic joint handles rig movement, the closure device provides pressure containment, the damper system manages pressure fluctuations, and the diverter handles kicks. This multi-functional integration enables managed pressure drilling and mud cap drilling operations without requiring separate complex pressure control systems, thus improving drilling efficiency while avoiding excessive system complexity.
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 maintains constant fluid pressure in the riser annulus, simplifies installation and maintenance, and allows for real-time pressure regulation, reducing the risk of pressure spikes and enabling efficient drilling operations during managed pressure drilling or mud cap drilling.
Implementation Method 1
a damper system which comprises a vessel which is divided into first and second substantially fluid tight chambers by means of a movable divider, the first chamber being connected to the fluid flow line and the second chamber being connected to a pressurised fluid reservoir
Implementation Method 2
Seals are provided between the outer and inner tube sections, and these substantially prevent leakage of fluid from the riser whilst allowing the inner tube section to slide relative to the outer tube section
Implementation Method 3
the damper system further including a pressure regulator device which is operable to control the pressure of fluid in the second chamber
Data Source
Figure 1
Figure 2
AI summary
A drilling system (10) including a drill string (13) which extends from a floating drilling rig to a well bore, and a tubular riser (12) which surrounds at least part of the portion of the drill string (13) between the well bore and drilling rig, the riser (12) having a telescopic joint (20) between a first tubular portion and a second tubular portion of the riser, the first tubular portion extending down to a well head at the top of the well bore and the second tubular portion extending up towards the drilling rig, the telescopic joint (20) comprising an inner tube part (20b) which is mounted within an outer tube part (20a), the drilling system (10) further including a riser closure device (26) which is mounted in the second tubular portion of the riser (12) and which is operable to provide a substantially fluid tight seal between the riser (12) and the drill string (13) whilst permitting the drill string (13) to rotate relative to the riser (12).