Borate-Modified Hydroxyethyl Cellulose for Shear-Rehealable Wellbore Fluids

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Solution Overview

Problem

Subterranean treatment fluids made with metal-crosslinked cellulosic polymers are not re-healable, leading to irreversible viscosity degradation under shear, which is not resilient for drilling and downhole operations, and they are not thermally stable.

Innovation Solution

Crosslinking modified hydroxyethyl cellulose polymers with borate crosslinking agents to form borate hydroxyethyl cellulose crosslinked complexes that provide rehealable and heat-tolerant viscosifying properties for use in downhole fluids, suitable for both oil-based and water-based fluids.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If metal ions such as zirconium and titanium are used to crosslink cellulosic polymers to provide sufficient viscosity, then the viscosity is maintained, but the fluid becomes not re-healable and viscosity degrades irreversibly under shearing

Engineering Contradiction:

Improveviscosity stabilityVSAvoidre-healability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent changes the chemical parameter of the crosslinking agent from metal ions (zirconium, titanium) to borate ions. This parameter change transforms the crosslinking mechanism from irreversible metal-polymer coordination to reversible borate ester formation, enabling the fluid to heal after shear degradation while maintaining sufficient viscosity through the crosslinked network structure.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the chemical mechanism of crosslinking from metal ion coordination (which creates permanent bonds) to borate ester formation (which creates dynamic, reversible bonds). This substitution allows the system to transition from a rigid, irreversible structure to a dynamic, self-healing structure that can reform crosslinks after shear stress.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Stability of the object's composition

If cellulosic polymers are crosslinked using metal ions to provide sufficient viscosity, then the viscosity is maintained, but the fluid is not thermally stable

Engineering Contradiction:

ImproveviscosityVSAvoidthermal stability

Core Design Contradiction:

Stability of the object's compositionVSTemperature

Solution Approach 1:

The patent changes the thermal stability parameter by replacing metal ion crosslinking with borate crosslinking. The borate ester crosslinks formed through this substitution exhibit superior thermal stability compared to metal-polymer complexes, allowing the fluid to maintain its viscosity and crosslinked structure at elevated downhole temperatures without degradation.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If naturally-derived polymeric viscosifying agents such as cellulose derivatives are used to reduce cost, then cost savings are achieved, but the viscosifying agent cannot maintain sufficient viscosity under downhole conditions

Engineering Contradiction:

ImprovecostVSAvoidviscosity maintenance

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The patent creates a composite system by combining naturally-derived hydroxyethyl cellulose polymer with borate crosslinking agents. This composite approach allows the inexpensive natural polymer to form a crosslinked network structure that maintains sufficient viscosity under downhole conditions, achieving both cost-effectiveness and performance reliability.

Inventive Principle:

Principle #40Composite materials

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 borate-crosslinked complexes maintain sufficient viscosity under shear and elevated temperatures, offering improved resilience and thermal stability, enabling effective fluid loss control and suspension properties in downhole applications.

Implementation Method 1

Crosslinking modified hydroxyethyl cellulose polymers with borate crosslinking agents to form borate hydroxyethyl cellulose crosslinked complexes

Methodology Applied

Scientific EffectCrosslinking: Chemical Bonding

Implementation Method 2

the viscosity of these fluids degrades irreversibly under shearing, and, therefore, is not resilient in drilling operations or other downhole operations that involve changes in shear

Methodology Applied

Scientific EffectViscoelasticity: Viscoelasticity

Implementation Method 3

the borate-crosslinked complexes maintain sufficient viscosity under shear and elevated temperatures, offering improved resilience and thermal stability

Methodology Applied

Scientific EffectThermal stability:

Data Source

PatentUS9879172B2Modified hydroxyethyl cellulosic polymers for improved well bore fluids and related uses

Publication Date: 2018.01.30 HALLIBURTON ENERGY SERVICES INC

AI summary

A method includes placing a downhole fluid including an aqueous base fluid and a viscosifying agent that includes a crosslinked borate-modified hydroxyethyl cellulose (mHEC) polymer in a wellbore penetrating a subterranean formation. Viscosifying agents include those whereby modified hydroxyethyl cellulose is crosslinked with a borate crosslinking agent to form a complex that has sufficient viscosifying and suspension properties to enable their use in downhole fluids.