Hang-off sub for steam injection rod suspension
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Solution Overview
Problem
Existing wellhead systems require sealing rams and stuffing boxes to prevent fluid flow during steam injection, which can be damaged by high temperatures and necessitate costly and time-consuming removal and replacement of the rod string, leading to operational inefficiencies and increased costs.
Innovation Solution
A hang-off sub system is used to suspend the sucker-rod string within the well, allowing steam injection without sealing rams or a stuffing box, using hang-off rams to support the rod string and a crossover for easy installation and removal, thereby avoiding seal degradation and reducing rig-time and operating costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sealing rams and stuffing boxes are used to prevent fluid flow during steam injection, then well control is improved, but the sealing components are damaged by high temperatures and require costly and time-consuming removal and replacement
Solution Approach 1:
The patent removes sealing rams and stuffing boxes from the system entirely, replacing them with a hang-off sub that suspends the rod string from the wellhead. This extraction eliminates the harmful interaction between high-temperature steam and temperature-sensitive sealing components, while well control is maintained through the hang-off mechanism that allows the well to be shut in without these components.
2Reliability
If sealing rams and stuffing boxes are installed to maintain well control, then fluid flow prevention is improved, but operational time and costs increase due to frequent removal and reinstallation
Solution Approach 1:
By removing sealing rams and stuffing boxes from the system and replacing them with a hang-off sub, the patent eliminates the need for repeated installation and removal cycles. The hang-off sub remains in place permanently, allowing steam injection operations to proceed without time-consuming interventions, thus reducing rig time and operational costs.
Solution Approach 2:
The patent replaces expensive, durable sealing components (sealing rams and stuffing boxes) with a simpler, more economical hang-off sub system. While the hang-off sub serves the same functional purpose, it is designed to be left in place indefinitely, eliminating the cyclical costs of removal, replacement, and reinstallation that characterize the traditional sealing component approach.
3Reliability
If sealing rams are used to control fluid flow during steam injection, then wellhead sealing is improved, but the sealing components degrade and require frequent replacement
Solution Approach 1:
The patent extracts sealing rams and stuffing boxes from the wellhead system, replacing them with a hang-off sub that achieves wellhead sealing through a different mechanism. This elimination prevents the thermal degradation that would otherwise limit the service life of sealing components during repeated steam injection operations.
Solution Approach 2:
The patent fundamentally changes the operational parameters of the wellhead system by transitioning from a sealing-based approach (relying on rubber or polymer seals that degrade at high temperatures) to a mechanical suspension approach (using metal-to-metal contact and gravity-based suspension). This parameter change allows the system to withstand high-temperature steam injection indefinitely without component degradation.
Data Source
AI summary
A hang-off system for suspending a rod string within a well is provided. In one embodiment, such a system includes a hang-off ram of a blowout preventer and a hang-off sub sized to fit within a bore of the blowout preventer. The hang-off ram and the hang-off sub have complementary surfaces that enable the hang-off ram to engage the hang-off sub within the blowout preventer to facilitate suspension of a sucker-rod string in a well from the hang-off sub. Additional systems, devices, and methods are also disclosed.