Subsea Annular Preventer Containment for Abandonment Operations
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Solution Overview
Problem
In offshore drilling, there is a need for effective environmental containment during upper abandonment operations, particularly when removing tubing and casing strings, as conventional methods may not prevent the release of trapped hydrocarbons or hazardous brines into the ocean.
Innovation Solution
A subsea containment system utilizing an annular preventer and running tool to engage and seal targets like tubing hangers, allowing for controlled fluid circulation and removal of contaminants, which can be adapted for various subsea operations including casing and wellhead systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a riser based subsea blowout preventer stack or Intervention Riser System is used for upper abandonment, then environmental containment is improved, but the system cannot be used when the outside diameter of tubing and casing strings prohibits riser installation
Solution Approach 1:
The containment system is divided into separate functional modules: an annular preventer for sealing, a running tool for engagement, and a circulation system for contaminant removal. This segmentation allows the system to be adapted to different well configurations without requiring a full riser stack.
Solution Approach 2:
The annular preventer acts as an intermediary device that provides sealing capability without requiring a physical barrier like a riser. It seals around the tubing or casing string directly, enabling containment in configurations where risers cannot be installed.
2Device complexity
If conventional abandonment methods are used without specialized containment equipment, then device complexity is reduced, but the risk of hydrocarbon and contaminant release into the environment increases
Solution Approach 1:
The annular preventer is deployed and sealed around the tubing or casing string before the actual abandonment operations begin. This preliminary sealing action ensures that any hydrocarbons or contaminants are contained before removal operations start, preventing environmental release.
Solution Approach 2:
The system uses hydraulic circulation to flush and remove contaminants from the wellbore under controlled conditions. Fluid is circulated through the well to carry contaminants to the surface for proper disposal, preventing direct environmental release.
3Reliability
If the annular preventer is closed to seal the running tool, then environmental containment is improved, but the running tool cannot be rotated or manipulated
Solution Approach 1:
The annular preventer is designed with dynamic sealing capabilities that allow it to maintain sealing effectiveness while accommodating the rotation and manipulation of the running tool. The sealing element can flex and adjust to maintain contact with the tool during operational movements.
4Productivity
If tubing and casing strings are removed during upper abandonment, then well completion is achieved, but trapped hydrocarbons and hazardous brines may be released into the ocean
Solution Approach 1:
The system converts the potential harm of trapped contaminants into a beneficial controlled removal process. By maintaining the seal with the annular preventer and using hydraulic circulation, contaminants that would otherwise be released are instead flushed to the surface in a controlled manner for proper disposal.
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 the safe and controlled removal of contaminants from subsea environments, ensuring environmental containment and compliance with regulations by effectively sealing and circulating fluids around tubing and casing components.
Implementation Method 1
closing the annular preventer
Implementation Method 2
circulating fluid about the target
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method and system of subsea containment which includes the steps of lowering the running tool into a subsea containment system, wherein the subsea containment system comprises an annular preventer, engaging the running tool to a target, closing the annular preventer, pulling up the target, and circulating fluid about the target. In a preferred method, rotating the running tool, cutting tubing, circulating the fluid at of the circulation line through the outlet, pulling the running tool out of the subsea containment system, and/or opening the annular preventer also performed. The target may be any item found in a subsea environment including a tubing hanger, a casing hanger, a tubing, a seal assembly, a component of a wellhead, or a component of the downhole completion.