Milling Rod Guide with Sacrificial Anode for Corrosion Mitigation

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Solution Overview

Problem

Current industry practices for oil wells with sucker rods and tubing do not effectively disintegrate sludge and flush out resulting grit, leading to corrosion and wear of tubing and rod strings.

Innovation Solution

The implementation of a milling rod guide system, which includes milling rod guides with hardened milling heads and a sacrificial anode, to disintegrate sludge and reduce grit particle size, thereby facilitating the flushing of grit out of the well while mitigating corrosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If current industry practices use steel rods and tubing with softer components, then the system is easier to manufacture and operate, but corrosion and wear from grit and sludge accelerate component degradation

Engineering Contradiction:

Improvecomponent lifeVSAvoidcorrosion and wear

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful grit and sludge into a beneficial abrasive medium by introducing hardened milling heads that utilize the grit particles to mill and clean the rod and tubing surfaces. The previously harmful abrasives become the tool for surface conditioning and corrosion prevention.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the hardness parameter of specific components by introducing hardened milling heads (60-65 HRC) and abrasive elements, transforming the soft steel-on-steel contact into a controlled abrasive process that prevents corrosion while managing wear through material selection.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If milling rod guides with hardened milling heads are installed, then sludge disintegration and grit flushing effectiveness improve, but device complexity increases

Engineering Contradiction:

Improvesludge disintegration efficiencyVSAvoidsystem structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The milling rod guide serves multiple functions simultaneously: it guides the rod string, mills sludge and grit, conditions rod and tubing surfaces, and prevents corrosion. This multi-functionality justifies the added complexity by delivering several benefits from a single integrated component.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses the rod string's own reciprocating motion to power the milling action, requiring no external power source. The rod string serves itself by providing both the driving force and the object to be conditioned, simplifying the overall system despite the added milling components.

Inventive Principle:

Principle #25Self-service

3Reliability

If corrosion inhibitor is applied to steel surfaces, then corrosion protection is provided, but the inhibitor film is mechanically scraped off during rod reciprocation exposing bare steel to corrosion

Engineering Contradiction:

Improvecorrosion protectionVSAvoidinhibitor film integrity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent replaces the mechanical corrosion protection method (inhibitor film) with an electrochemical method (cathodic protection). The sacrificial anode provides continuous corrosion protection without relying on a mechanical film that can be scraped off, fundamentally changing the protection mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The sacrificial anode acts as an intermediary between the corrosive environment and the protected steel components. It preferentially corrodes to protect the rods and tubing, serving as a mediator that sacrifices itself to preserve the primary system components.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 milling rod guide system effectively disintegrates sludge, reduces grit particle size, and flushes out grit from the well, thereby prolonging the life of the well and reducing corrosion and wear on tubing and rod strings.

Implementation Method 1

providing galvanic protection with a sacrificial anode when a corrosion inhibitor film is mechanically scraped off an inner surface of the tubing

Methodology Applied

Scientific EffectGalvanic protection: Galvanometer

Data Source

PatentUS12221838B1Milling rod guides and methods

Publication Date: 2025.02.11 COPELAND CARTER D

AI summary

Milling rod guide (MRG) systems for oil wells include one or more relatively short rods with hardened milling heads (couplings) and sacrificial anode material located centrally on the body rod body between the milling heads. When driven in a reciprocating motion inside conventional or hardened tubing, the interfaces between the MRGs and the tubing repeatedly crush, grind, and tumble grit into smaller particles. At some smaller size, the solids can then be lifted out of the well with the production. The sacrificial anode section provides cathodic protection of metal surfaces when corrosion inhibitor films are removed. Channels within the anode allow solids to pass through the MRG for further milling or to be produced. MRGs distribute and reduce the radial and shear stresses at the interfaces of the of the rod string and the tubing in vertical, deviated, inclined, or horizontal sections of the pumping system, thereby mitigating wear.