Subsea Tubing Hanger Alignment Ring Orientation
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Solution Overview
Problem
The subsea installation of a tubing hanger often results in misalignment due to manufacturing tolerances, incorrect guiding pin actuations, and operator errors, making it challenging to achieve proper orientation for subsequent Christmas tree installation.
Innovation Solution
A system utilizing an alignment ring with coarse and fine alignment features, secured to the subsea wellhead, guides the subsea tree into proper rotational orientation, eliminating the need for a conventional orientation helix and allowing real-time orientation control via a gyroscopic heading apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a guiding pin and helix interface is used to orient the tubing hanger, then rotational orientation is achieved, but misalignment occurs due to tolerance stack-up errors, incorrect actuation, and operator error
Solution Approach 1:
The alignment system is divided into two independent stages: coarse alignment using an alignment ring with alignment dogs, and fine alignment using a key and keyway mechanism. This segmentation allows each stage to perform its specific function within achievable tolerances, with the coarse alignment establishing a preliminary orientation and the fine alignment providing precise final positioning, thereby eliminating the cumulative tolerance stack-up errors of a single-stage system
Solution Approach 2:
The alignment ring is installed and secured to the wellhead before the tubing hanger is landed. This preliminary action establishes a fixed reference framework in advance, allowing the tubing hanger to be oriented relative to this pre-positioned structure rather than relying on post-installation adjustments, thus preventing misalignment from incorrect actuation and operator error
2Ease of operation
If a guiding pin and helix interface is used, then rotational orientation is attempted, but reliability is low due to multiple failure modes
Solution Approach 1:
The key and keyway mechanism is designed to automatically engage and self-align when the key is inserted into the keyway during tubing hanger rotation. This self-service mechanism eliminates the need for external actuation systems that can fail, ensuring reliable orientation achievement through inherent mechanical guidance and automatic engagement
Solution Approach 2:
The complex actuated guiding pin and helix interface is replaced with a simpler, more reliable mechanical system consisting of an alignment ring with alignment dogs for coarse alignment and a key-keyway mechanism for fine alignment. This substitution eliminates multiple potential failure points related to actuation systems while maintaining the essential rotational orientation function
Data Source
AI summary
A technique is provided for properly orienting a subsea tree with respect to a tubing hanger landed in a subsea wellhead. An alignment ring is rotationally positioned on the subsea wellhead such that a coarse alignment feature of the alignment ring is at a desired angular orientation with respect to a fine alignment feature on the tubing hanger. The alignment ring is then secured to the subsea wellhead. Subsequently, a subsea tree may be rotationally oriented with respect to the tubing hanger as the subsea tree is landed on the subsea wellhead. As the subsea tree engages the coarse alignment feature, the coarse alignment feature guides the subsea tree into engagement with the fine alignment feature of the tubing hanger to ensure proper rotational orientation as landing of the subsea tree is completed.