Subsea Winch Powered Sheave Cable Descent
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Solution Overview
Problem
At depths greater than 500 meters, the wireline cable in subsea well deployment systems experiences increased frictional resistance and drag-induced upward pull due to currents, which can prevent tools from descending into the well, as the cable becomes horizontally oriented and the downward pull force is overcome by frictional resistance and drag.
Innovation Solution
A subsea winch with powered sheaves and a movable, self-aligning inlet with low friction materials or mechanisms, such as rollers or ball bearings, that increases the downhole pull force on the cable to overcome frictional resistance and drag, allowing the tool to progress down the well by enhancing the tension applied by the tool's weight or tractor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the wireline cable enters the well in a substantially vertical orientation at depths of 500 meters or less, then the frictional resistance between the cable and subsea apparatus is minimized, but at depths greater than 500 meters the cable becomes dragged into a curved shape with horizontal entry angle, causing increased frictional resistance and drag-induced upward pull that prevents tool descent
Solution Approach 1:
The patent converts the harmful drag force and frictional resistance into beneficial downward pull force by using a powered sheave system. The sheave applies frictional engagement to the cable in the downward direction, transforming the resistance forces into useful propulsion force that helps overcome the horizontal cable orientation and enables tool descent into the wellbore.
Solution Approach 2:
The powered sheave acts as an intermediary device between the tool string and the cable. It receives the cable, applies controlled frictional force through the powered surface, and transfers the amplified downward pull force back to the cable, thereby mediating the interaction between the tool weight and the resistive forces from drag and friction.
2Reliability
If a friction drive system is used to increase downhole pull force on the cable, then the tool can progress down the well despite drag and friction, but the device complexity increases with powered sheaves and low friction mechanisms
Solution Approach 1:
The housing inlet is designed to perform multiple functions: it serves as the entry point for the cable, provides a low friction interface through rollers or ball bearings, and can be oriented to optimize cable alignment. This multi-functionality reduces the need for separate components, thereby managing device complexity while maintaining reliability.
Solution Approach 2:
The low friction mechanism at the housing inlet, such as rollers or ball bearings, provides self-service by automatically reducing frictional resistance as the cable passes through, without requiring external control or adjustment. This self-adjusting feature simplifies the overall system while ensuring reliable operation under varying load conditions.
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
The subsea winch effectively counters the upward pull and frictional resistance, ensuring the tool can be lowered into the well by increasing the downhole pull force on the cable, thereby facilitating successful deployment at greater depths.
Implementation Method 1
the or each powered sheave having a surface adapted to form a frictional engagement with a cable passing between the inlet and the outlet via the at least one sheave
Implementation Method 2
The housing inlet may comprise a low fiction mechanism such as rollers or ball bearings
Implementation Method 3
The housing inlet may comprise a low fiction mechanism such as rollers or ball bearings
Data Source
AI summary
A subsea winch is described. The subsea winch comprises a housing adapted to be attached to a well intervention system, the housing having an inlet and an outlet and at least one powered sheave arranged between the inlet and the outlet, the or each powered sheave having a surface adapted to form a frictional engagement with a cable passing between the inlet and the outlet via the at least one sheave. In use, a pull force pulling the cable in a downhole direction applied to the cable by a tool string being lowered into the well intervention system is increased by the winch such that the downhole pull force on the cable at the housing inlet is greater than the downhole pull force at the housing outlet.