Degradable Buoyant Plug for Casing Drag Reduction

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Solution Overview

Problem

In hydrocarbon wells, especially horizontal and deviated wells, the friction between the casing and the wellbore creates significant drag, making it difficult to run the casing to great depths due to insufficient weight in the vertical section, and existing solutions like rupture disc assemblies can damage equipment with debris and restrict the casing's inner diameter.

Innovation Solution

A degradable plug assembly is used within the casing string to create a buoyant chamber by trapping a lightweight fluid, reducing the overall weight and drag of the casing, while preventing debris from obstructing the casing's inner diameter by containing and removing the degradable plug fragments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If a rupture disc assembly is used to reduce casing weight, then the casing can be run to greater depths, but debris is generated that damages equipment and restricts the casing's inner diameter

Engineering Contradiction:

Improvedepth to which casing can be runVSAvoiddebris damage and inner diameter restriction

Core Design Contradiction:

Length of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent employs a degradable plug made of biodegradable material that is intentionally designed to break down after serving its temporary purpose of providing buoyancy. This disposable approach eliminates the need for complex retrieval mechanisms and prevents long-term debris issues, as the material degrades naturally into harmless substances.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the physical and chemical parameters of the plug material over time. The biodegradable material transitions from a solid, structurally intact state during casing installation to a degrading state, eventually becoming a slurry or liquid that can be pumped through the casing. This parameter change resolves the contradiction by transforming the potential harmful debris into a beneficial fluid.

Inventive Principle:

Principle #35Parameter changes

2Length of moving object

If the casing weight is increased to overcome friction in vertical sections, then the casing can be run deeper, but the drag in horizontal and deviated sections increases due to insufficient weight distribution

Engineering Contradiction:

Improvedepth to which casing can be runVSAvoiddrag force in wellbore

Core Design Contradiction:

Length of moving objectVSForce

Solution Approach 1:

The patent introduces a buoyant force as a counterweight to the gravitational force acting on the casing. By filling a portion of the casing with a lightweight fluid and sealing it with a degradable plug, the system creates an upward buoyant force that offsets the downward weight, reducing the net force and frictional drag between the casing and wellbore, particularly in horizontal and deviated sections.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

3Length of moving object

If a degradable plug is used to create buoyancy, then the casing can be run to greater depths, but the plug must be reliably contained and removed without obstructing the casing

Engineering Contradiction:

Improvedepth to which casing can be runVSAvoidreliable containment and removal of plug fragments

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The degradable plug is designed to automatically degrade and transform into a pumpable slurry or liquid through exposure to downhole conditions such as temperature, pressure, and chemical environment. This self-service mechanism eliminates the need for manual intervention or complex retrieval systems, as the plug autonomously transitions from a solid barrier to a fluid that can be circulated through the casing without obstruction.

Inventive Principle:

Principle #25Self-service

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 the casing to be run to greater depths and non-vertical distances without damaging debris or restricting the casing's inner diameter, facilitating completion of wells by reducing frictional forces and maintaining operational integrity.

Implementation Method 1

A degradable plug assembly is used within the casing string to create a buoyant chamber by trapping a lightweight fluid

Methodology Applied

Scientific EffectBuoyancy: Archimedes' Principle (Buoyancy)

Implementation Method 2

The degradable plug portion can be made of a material that degrades, deteriorates and/or dissolves upon exposure to a fluid (e.g., water, well fluid, or other substance present in the wellbore)

Methodology Applied

Scientific EffectDissolution: Solvation

Data Source

PatentUS11639641B2Degradable in-line buoyant system for running casing in a wellbore

Publication Date: 2023.05.02 KLX ENERGY SERVICES LLC

AI summary

A tool for running a casing string assembly into a wellbore includes a degradable plug assembly that temporarily isolates light fluid trapped in a lower portion of the casing string from heavier fluid in the upper portion of the casing string, thereby reducing the horizontal weight of the casing string by an amount sufficient to overcome a drag force. After the casing string is landed at a final location in the wellbore, fluid is introduced to the degradable plug assembly to degrade the plug and clear the axial passageway of the casing string so that tools or other equipment can pass therethrough.