Rotary Steerable Pad Control for Constant Wellbore Curvature
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Solution Overview
Problem
Conventional 'push-the-bit' rotary steerable systems (RSS) face issues with passive steering member retraction, leading to undesired consumption of lateral force and inability to control steering rate, resulting in non-constant wellbore curvature.
Innovation Solution
A rotary steerable system (RSS) with a steering section, hydraulics section, and instrumentation section, featuring a rotationally geostationary primary valve and secondary valve, which provides dependent control of steering member extension and active retraction, using a fluid manifold to manage fluid flow for precise wellbore profiling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive steering member retraction is used, then the system structure is simpler, but lateral force is consumed undesirably and steering rate cannot be controlled
Solution Approach 1:
The steering member uses its own stored elastic energy to retract automatically after pushing against the wellbore wall. The elastic element deforms during extension and then restores, pulling the steering member back without requiring external hydraulic pressure or complex active retraction mechanisms.
Solution Approach 2:
The patent removes the need for active hydraulic retraction systems by extracting the retraction function and implementing it through passive elastic recovery. This eliminates the complexity of additional actuators and control systems while maintaining effective steering member retraction.
2Device complexity
If passive steering member retraction is used, then the system is simpler, but steering rate cannot be controlled resulting in non-constant wellbore curvature
Solution Approach 1:
The system uses inclination sensors to detect the actual wellbore trajectory and feeds this information back to the control system. The control system then adjusts the extension timing and duration of steering members to achieve the desired wellbore curvature profile, enabling precise control of steering rate and wellbore geometry.
Solution Approach 2:
The patent implements dynamic control by varying the extension timing and duration of steering members based on real-time wellbore conditions. The system adapts the steering action continuously during drilling to maintain the desired curvature profile, transitioning from static to dynamic steering control.
3Ease of operation
If steering member extension is controlled independently, then ease of operation is improved, but lateral force consumption increases and steering efficiency decreases
Solution Approach 1:
The patent merges the control of multiple steering members into a coordinated system where members are extended and retracted in sequence rather than independently. This synchronized operation ensures that only the necessary number of steering members are active at any time, reducing redundant lateral force application and improving overall steering efficiency.
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 quicker and more controlled steering member retraction, allowing for precise wellbore curvature and improved steering rate management, reducing unwanted contact with the wellbore and enhancing drilling efficiency.
Implementation Method 1
Each steering member has a contact surface that is contoured for contacting engagement with the generally cylindrical wall of the wellbore being drilled. These steering members can be selectively extended or deflected radially outward from the rotating steering head (typically by means of hydraulic pressure provided by drilling fluid flowing downward through the drill string to the drill bit) to exert laterally compressive forces against the wellbore wall.
Implementation Method 2
a rotationally geostationary primary (or 'main') valve and a secondary valve that controls fluid flow to the primary valve
Data Source
AI summary
A push-the-bit steering tool for drilling deviated wellbores comprises a steering head mountable to the bottom of a drill string and having steering pads extendable and retractable by fluid-actuated pistons; a fluid manifold co-rotatingly mounted to the steering head for delivering fluid to the pistons; a rotationally geostationary primary valve for delivering fluid to the fluid manifold; and a secondary valve for delivering fluid to the primary valve. The primary valve has a flow restrictor for regulating fluid flow to the pistons such that the steering pads will be sequentially actuated as the drill string rotates, and the steering force exerted against the wellbore by each sequentially-actuated steering pad will be in a constant selected direction. All of the pistons are hydraulically connected, thereby enabling dependent control of steering pad extension and dependent and positive control of steering pad retraction.