Downhole Flow Control Choke With Wear-Decoupled Seal Surfaces
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Solution Overview
Problem
Existing flow control chokes in drilling systems suffer from abrasion and erosion wear, leading to premature failure and loss of flow restriction capability, which compromises the reliability and performance of hydraulic systems in directional drilling.
Innovation Solution
The design separates abrasion and erosion wear mechanisms by decoupling the contact surfaces, using a rotating choke and stationary seat with angled flow ports and a biasing mechanism to control bypass flow, allowing for independent material selection for abrasion and erosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flow control choke with metal-to-metal contact surfaces is used to control bypass flow, then flow restriction capability is achieved, but abrasion and erosion wear occur at the contact surfaces and flow ports, leading to premature failure
Solution Approach 1:
The choke assembly is segmented into distinct functional zones: a seal contact surface area where the rotating choke carrier contacts the stationary seat, and a flow restriction area with flow ports. This segmentation separates the wear mechanisms - abrasion occurs at the seal contact surface while erosion occurs at the flow ports, preventing combined wear acceleration and extending service life.
Solution Approach 2:
The flow restriction function is extracted from the metal-to-metal contact surface and relocated to separate flow ports in the stationary seat. This extraction prevents the contact surface from being subjected to both abrasion and erosion, as the high-velocity fluid flow is directed through dedicated flow ports away from the seal contact area.
2Reliability
If radial bearing gaps are used to control bypass flow, then some flow restriction is achieved, but rapid wear of radial bearings occurs, causing excessive flow loss
Solution Approach 1:
The flow control function is segmented from the radial bearing gaps and assigned to a dedicated choke assembly with controlled flow ports. This separates the bearing's lubrication function from the flow restriction function, allowing the bearings to wear at a normal rate while the choke assembly provides stable, long-term flow control through its hardened seal surfaces and flow restriction geometry.
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
This separation significantly increases the lifespan and reliability of the flow control choke, maintaining hydraulic pressure for pad extension and enhancing the overall performance of the drilling system.
Implementation Method 1
a friction surface of the rotating choke contacts a friction surface of the stationary seat to restrict the amount of bypass fluid
Implementation Method 2
a biasing mechanism applying a biasing force to press the rotating choke against the stationary seat
Implementation Method 3
erosion wear may be formed at or near the same location... erosion at the flow ports/orifices which are right at the metal-to-metal contact surface
Implementation Method 4
accelerated abrasion (or 3-body abrasion—two metal and abrasive particles in the mud)
Data Source
AI summary
Shown and described herein is a choke assembly for use with a downhole drill string. The choke assembly may include a rotating choke carrier, a stationary seat disposed on the rotating choke carrier and a rotating choke positioned adjacent to the stationary seat to create a seal surface. The choke assembly may further comprise a biasing mechanism applying a biasing force to press the rotating choke against the stationary seat and a flow port within the stationary seat which controls drilling fluid to allow some drilling fluid to become a bypass fluid and pass through the stationary seat.