Load Cross-Over Slip-Joint Mechanism for Downhole Tool Assembly
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Solution Overview
Problem
The existing methods for assembling and disassembling lengthy tool assemblies in oil and gas operations are cumbersome and time-consuming, particularly on the rig floor, due to the need for making up both the inner mandrel and external cylinder assemblies, which often requires pressure testing that can be difficult or impossible to conduct effectively.
Innovation Solution
A downhole tool assembly design featuring a mandrel assembly that bears tensile and rotational loads, with a displacement assembly providing relative movement, and a load cross-over joint that transfers loads between the upper and lower mandrels, allowing for easier assembly and disassembly without the need for pressure testing, by reversing the loading of inner and outer members through a crossover body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the external cylinder assembly and internal mandrel assembly are made up separately with seals on the rig floor, then the tool assembly can be assembled on location, but the process becomes cumbersome and time-consuming requiring pressure testing
Solution Approach 1:
The tool assembly is divided into an outer assembly and an inner assembly that can be made up separately and independently. The outer assembly includes the outer piston assembly and outer bonnet, while the inner assembly includes the inner piston assembly and inner bonnet. These segmented assemblies can be prepared separately on the rig floor without requiring complex sealing operations, and then coupled together through a simplified connection process at the crossover body.
Solution Approach 2:
The crossover body serves as an intermediary component that couples the inner and outer assemblies. It provides a simplified connection interface where the inner bonnet connects to the outer bonnet through a straightforward mechanical coupling rather than requiring complex sealed joints. This intermediary structure eliminates the need for pressure testing during assembly while ensuring proper load transfer between the inner and outer components.
2Adaptability or versatility
If a non-load bearing external cylinder is used for setting the tool, then relative motion for setting is achieved, but the make-up process becomes cumbersome requiring seals and pressure testing
Solution Approach 1:
The patent inverts the traditional arrangement by making the outer cylinder assembly load-bearing rather than non-load bearing. The outer piston assembly and outer bonnet are designed to carry tensile and rotational loads, while the inner assembly provides the setting motion. This inversion eliminates the need for complex sealed connections between separate assemblies, as the load paths are clearly defined and the crossover body provides a simple mechanical coupling interface.
Solution Approach 2:
The outer bonnet serves multiple functions: it acts as the external cylinder for setting operations, provides structural support for load-bearing, and serves as the coupling interface for the inner bonnet through the crossover body. This multi-functionality reduces the overall complexity by eliminating dedicated sealed connections, as the outer bonnet's structural role integrates with its setting function.
3Reliability
If pressure testing is required after assembly on rig floor, then sealing integrity can be verified, but the process becomes awkward and time-consuming or even impossible
Solution Approach 1:
The patent extracts the sealing requirements from the connection between separate outer and inner assemblies. By designing the crossover body with a simplified mechanical coupling interface, the need for complex sealed joints is eliminated. The connection between the inner bonnet and outer bonnet through the crossover body does not require seals, thereby removing the need for pressure testing while maintaining structural integrity and load transfer capability.
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
A downhole tool assembly is presented for use in a wellbore, the tool having a mandrel assembly for substantially bearing the tensile and rotational loads placed on the tool assembly during run-in to the wellbore, a displacement assembly for substantially bearing displacement loads and for providing relative movement to the mandrel assembly, the displacement assembly for actuating a actuable tool attached to the mandrel assembly. The mandrel assembly has an upper mandrel positioned radially outward of the displacement assembly and a lower mandrel positioned radially inward of the displacement assembly. A load cross-over mandrel transfers the tensile and rotational loads between the upper and lower mandrels. The load cross-over mandrel has a plurality of passages which allow corresponding rods of the displacement assembly to slide therethrough. The rods transfer the displacement loads from actuators above the rods to an actuable tool below the rods.