Drill String Stiction Control via Periodic Pulsing

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Solution Overview

Problem

During subterranean drilling, the transition from a static frictional regime to a dynamic frictional regime often results in sudden jerking of the drill string, leading to overshoot and potential damage to the drill bit or drilling rig, due to the higher forces required to overcome static friction.

Innovation Solution

A closed-loop system is implemented that uses sensors to measure physical parameters such as weight on bit and friction coefficients, allowing for controlled pulsing of the drill string in predetermined longitudinal increments to gradually transition from static to dynamic friction, reducing the overshoot distance through precise axial movement control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a force is applied to overcome static friction, then the drill string can transition to dynamic movement, but the drill string experiences sudden jerking and overshoot that can cause damage

Engineering Contradiction:

Improvedrill string safetyVSAvoiddrill string movement control

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent applies periodic pulsing action to the drill string, creating a series of controlled force impulses that gradually overcome static friction. Instead of a single large force that causes jerking, the system uses multiple smaller pulsing forces applied in sequence, allowing the drill string to move incrementally from static to dynamic state without sudden shocks or overshoot.

Inventive Principle:

Principle #19Periodic action

2Productivity

If the drill string is weighted to optimize rate of penetration, then drilling speed increases, but friction forces become more pronounced and can cause stiction

Engineering Contradiction:

Improverate of penetrationVSAvoidfriction force

Core Design Contradiction:

ProductivityVSForce

Solution Approach 1:

The system uses periodic pulsing to counteract the increased friction forces resulting from higher drill string weight. The pulsing mechanism delivers controlled force impulses that overcome the elevated static friction without requiring proportionally higher continuous weight, thus maintaining optimized rate of penetration while preventing stiction during pauses.

Inventive Principle:

Principle #19Periodic action

3Ease of operation

If a large force is applied to break out of static friction, then the drill string can move, but the overshoot can damage the drill bit or drilling rig

Engineering Contradiction:

Improvedrill string movement initiationVSAvoidovershoot damage risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent implements a cushioning effect by using pulsing forces that build up movement gradually. Each pulse is controlled to deliver just enough force to advance the drill string a predetermined increment, preventing excessive force accumulation that would cause overshoot. The pulsing sequence acts as a cushion, distributing the breakout force over time and preventing sudden shocks to the drill bit and rig.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

By applying forces periodically through pulsing rather than continuously or in a single large impulse, the system breaks down the static friction overcome process into controlled stages. This periodic application allows the system to monitor and control the transition from static to dynamic movement, preventing the accumulation of excess force that would result in damaging overshoot.

Inventive Principle:

Principle #19Periodic action

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 approach minimizes drill string overshoot, reducing the risk of damage and enhancing drilling efficiency by maintaining a controlled force application, thus lowering operational costs and improving drilling precision.

Implementation Method 1

the forces required to overcome static friction are typically greater than that necessary to affect continued relative movement of the drill string

Methodology Applied

Scientific EffectStatic friction: Static Friction

Implementation Method 2

One particular force of concern during subterranean drilling is the force of friction resulting from relative movement (or lack thereof) between the inner surface of the wellbore and the outer surface of the drill string

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 3

This sudden jerking can cause the drill string to overshoot on a downhole control parameter

Methodology Applied

Scientific EffectInertia: Inertia

Data Source

PatentUS9771788B2Stiction control

Publication Date: 2017.09.26 CANRIG DRILLING TECHNOLOGY LTD

AI summary

A system for use in subterranean operations comprising a drill string positioned within a wellbore, a sensor adapted to sense a physical parameter in relation to the drill string and generate a signal representing the physical parameter, and a control member adapted to affect subterranean longitudinal movement of the drill string in a predetermined longitudinal sequence of increments within the wellbore in response to the signal.