Wellhead Assembly for Injection Tubing String
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Solution Overview
Problem
Traditional wellhead assemblies for coiled tubing strings are expensive and require costly and time-consuming processes to install, maintain, and remove, especially when dealing with injection tubing strings, as they often necessitate severing the tubing and mobilizing workover rigs to manage back pressure and master valve operations.
Innovation Solution
A wellhead assembly comprising a flange, mandrel, and hanger with polished bore receptacles and seals, allowing for secure and leak-proof communication between the injection tubing string and the wellhead, enabling fluid injection without disrupting existing flow lines or requiring extensive modifications, and allowing for the use of a live swivel to prevent rotation transmission to the tubing string.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a Y-body Christmas tree is used for injection tubing string installation, then convenient access for injecting coiled tubing is achieved, but the tree becomes more expensive and operational flexibility is reduced
Solution Approach 1:
The invention divides the wellhead system into separate functional components: a conventional Christmas tree structure and a独立的 injection tubing hanger assembly. This segmentation allows the injection function to be added without modifying the main tree structure, avoiding complexity while maintaining operational convenience.
Solution Approach 2:
The injection tubing hanger is nested within the conventional Christmas tree structure, with the hanger landing in the production tubing hanger's polished bore receptacle. This nesting approach allows the injection system to be integrated into the existing tree without adding external complexity, while still providing convenient injection access.
2Reliability
If the lower master valve is closed to obtain a double barrier, then safety is improved, but the injection tubing string must be severed requiring expensive fishing operations
Solution Approach 1:
The invention segments the tubing system into production tubing and injection tubing as separate strings. The injection tubing has its own dedicated hanger and polished bore receptacle, allowing it to be independently installed and removed. This segmentation enables the lower master valve to be closed for safety without affecting the injection tubing, eliminating the need for costly fishing operations.
Solution Approach 2:
The injection tubing hanger acts as an intermediary component that provides a dedicated interface for injection tubing installation. This hanger with its polished bore receptacle allows the injection tubing to be suspended independently from the production tubing system, enabling safe valve operations without compromising the injection string integrity.
3Reliability
If the back pressure valve preparation in the tubing hanger is used, then back pressure control is achieved, but the injection tubing string must be removed first
Solution Approach 1:
The invention creates separate functional zones: the production tubing system with its back pressure valve preparation, and the injection tubing system with its own hanger and polished bore receptacle. This segmentation allows both functions to coexist independently, enabling back pressure valve installation without removing the injection tubing string, thereby improving operational efficiency.
4Ease of repair
If workover rig is mobilized to remove injection tubing string, then master valve repair is enabled, but time and cost increase significantly
Solution Approach 1:
By segmenting the injection tubing into a separate string with its own hanger assembly, the invention allows the injection tubing to remain in place while the production tubing system is accessed for master valve repairs. This eliminates the need to mobilize workover rigs for routine valve maintenance, significantly reducing downtime and costs.
Data Source
AI summary
A wellhead assembly for an injection tubing string is provided which allows a master valve to be closed without damaging the injection tubing string while still allowing for the use of a back pressure valve to isolate the tree. Wellhead assemblies and related methods of the present invention include a wellhead apparatus adapted to be connected to a wellhead. The assembly also includes a mandrel adapted to being inserted into the longitudinal bore of the wellhead apparatus, the mandrel having a port for communicating with an injection port which extends radially through the wellhead apparatus. The assembly further includes a hanger adapted to connect to the upper end of the injection string, wherein the hanger is further adapted to land in the longitudinal bore of the mandrel. The hanger includes a communication passageway for facilitating fluid communication between the port of the mandrel and the injection tubing string.