Riser Isolation Tool for Deepwater Well Pressure Containment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Deep-water drilling marine risers often burst or collapse under excessive pressures during well-killing operations or BOP failures, leading to uncontrolled fluid influx and environmental hazards.
Innovation Solution
A riser isolation tool (RIT) with a tubular structure and seal stinger is installed inside the marine riser, featuring higher burst and collapse pressure ratings than the riser itself, to mechanically isolate the riser and subsea BOP from the wellbore, using materials like 2014 aluminum alloy with increased wall thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional marine riser is used during deep-water drilling, then the riser can accommodate rig heave through slip joints and flexible connections, but the riser bursts or collapses under excessive pressures during well-killing operations or BOP failures
Solution Approach 1:
The riser isolation tool is nested inside the conventional marine riser, forming a concentric structure where the RIT (with higher pressure rating) is positioned within the lower-pressure-rated riser. This nesting allows the inner RIT to bear the excessive wellbore pressures while the outer riser continues to provide structural support and accommodate rig heave movements through its slip joints and flexible connections.
Solution Approach 2:
The riser isolation tool acts as an intermediary barrier between the wellbore environment and the conventional marine riser. By installing the RIT inside the riser and sealing it against the wellbore, the tool mediates the pressure transmission, protecting the outer riser structure from direct exposure to excessive pressures during well-killing operations or BOP failures.
2Strength
If the riser wall thickness is increased to withstand higher pressures, then the pressure rating improves, but the riser weight and installation complexity increase
Solution Approach 1:
The pressure containment function is segmented between two separate structures: the conventional marine riser (optimized for structural support and flexibility) and the riser isolation tool (optimized for high pressure containment). This segmentation allows each component to be designed for its specific function, avoiding the need to increase the weight of the entire riser system to achieve high pressure ratings.
Solution Approach 2:
The riser isolation tool employs composite construction with a high-strength alloy steel body (such as 13-5 Mo or 2014 aluminum alloy) and may include additional reinforcement layers or coatings. This composite approach enables the RIT to achieve exceptional burst pressure ratings (exceeding 10,000 psi) while maintaining a manageable weight that can be handled by conventional drilling equipment.
3Reliability
If a riser isolation tool with higher pressure ratings is installed inside the marine riser, then the pressure containment capability increases, but the device complexity and installation procedures increase
Solution Approach 1:
The riser isolation tool is designed as a multi-functional device that simultaneously provides: (1) high-pressure containment during well-killing operations, (2) a sealed environment for subsequent wellbore operations, (3) structural support for the drill string, and (4) a platform for installing additional well control equipment. This multi-functionality consolidates multiple requirements into a single device, reducing overall system complexity despite the added pressure containment capability.
Solution Approach 2:
The riser isolation tool is installed in advance, before high-pressure well-killing operations are required. This preliminary installation ensures that the high-pressure containment structure is already in place and properly sealed before critical operations begin, simplifying the overall process by eliminating the need for complex pressure containment measures during emergency well-killing scenarios.
Data Source
AI summary
In a subsea drilling operation, a riser isolation tool may be installed inside a marine riser between the subsea wellhead and the rig floor to provide a conduit having a higher pressure rating than the original riser itself. In some embodiments, the riser isolation tool includes a tubular body and, extending therefrom, a seal stinger sized to be slidably received in a receptacle seated in the wellhead. Additional apparatus, systems, and methods are disclosed.