Borate Crosslinked Polysaccharide Fluids for High TDS Produced Water

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Solution Overview

Problem

Hydraulic fracturing operations face challenges in maintaining stable viscosity of fracturing fluids with high total dissolved solids (TDS) due to pH instability, leading to reversible boron crosslinking and decreased effectiveness, especially at elevated bottom-hole temperatures.

Innovation Solution

A composition comprising a boron-crosslinked polysaccharide polymer and an alkylamine pH buffer, such as diethylenetriamine, is used to maintain stable crosslinking and viscosity in fracturing fluids with high TDS levels, preventing pH reversal and precipitation issues caused by calcium and magnesium ions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If produced water with high TDS is used as fracturing fluid, then water cost is reduced and fresh water resources are conserved, but pH stability deteriorates leading to reversible boron crosslinking and viscosity loss

Engineering Contradiction:

Improveproduced water usageVSAvoidpH stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

A pH buffer system comprising carbonate, bicarbonate, and hydroxide ions is introduced as an intermediary to mediate between the high TDS produced water and the boron crosslinking agent. This buffer system maintains pH within the optimal range of 8.0-10.0, preventing premature reversal of boron crosslinking while allowing the use of produced water with high calcium and magnesium content.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the pH parameter control strategy by using a multi-component buffer system that maintains pH in the range of 8.0-10.0. This parameter control ensures stable boron crosslinking in high TDS produced water, preventing viscosity loss while enabling the use of produced water as a cost-effective fluid source.

Inventive Principle:

Principle #35Parameter changes

2Strength

If boron crosslinking is used to increase viscosity, then proppant transport capability is improved, but crosslinking reversibility occurs at elevated temperatures reducing fluid stability

Engineering Contradiction:

ImproveviscosityVSAvoidcrosslinking stability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The pH buffer system acts as a feedback mechanism that continuously maintains pH within the optimal range for boron crosslinking stability. By monitoring and adjusting pH through the carbonate-bicarbonate-hydroxide buffer system, the patent prevents crosslinking reversal at elevated bottom-hole temperatures, ensuring reliable viscosity and proppant transport capability throughout the fracturing operation.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The pH buffer system provides beforehand cushioning by pre-establishing a chemical buffer capacity that anticipates and prevents pH drops that would cause crosslinking reversal. This protective buffer system is incorporated into the fracturing fluid formulation to cushion against temperature-induced pH changes and maintain crosslinking stability throughout the wellbore temperature gradient.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Stability of the object's composition

If pH is elevated above 8.0 to maintain boron crosslinking, then crosslinking stability is improved, but calcium and magnesium precipitation increases

Engineering Contradiction:

Improvecrosslinking stabilityVSAvoidprecipitation

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent optimizes the pH parameter to a specific range of 8.0-10.0, which is high enough to maintain boron crosslinking stability but controlled to minimize excessive calcium and magnesium precipitation. This parameter optimization, combined with the buffer system, achieves crosslinking stability while managing precipitation issues in high TDS produced water.

Inventive Principle:

Principle #35Parameter changes

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 solution ensures stable viscosity and effective transport of proppants, reducing leak-off and maintaining fluid stability at elevated temperatures, even in fluids with high TDS levels, thereby enhancing the efficiency and cost-effectiveness of hydraulic fracturing operations.

Implementation Method 1

a boron compound and pH buffer to improve the functionality and stability of the viscosity of the fluid

Methodology Applied

Scientific EffectBoron crosslinking: Chemical Bonding

Implementation Method 2

When hydrated, these polymers form gels that increase the viscosity of the fracturing fluid

Methodology Applied

Scientific EffectGel formation: Gel

Implementation Method 3

Methodology Applied

Scientific EffectpH buffering:

Data Source

PatentUS10808166B2Produced water borate crosslinking compositions and method of use

Publication Date: 2020.10.20 ENERGY SOLUTIONS US LLC

AI summary

A composition and method for treating a fracturing fluid comprising produced water with high levels of dissolved solids using a polymer crosslinked with a boron compound and a high pH alkylamine buffer. The composition improves the viscosity stability of the fracturing fluid at elevated bottom-hole temperatures, particularly when the fluid has high levels of calcium and magnesium. The composition is particularly useful with polysaccharides, including galactomannan gums, such as guar gum, locust bean gum, and karaya gum, and allows for the use of the preferred boron compound crosslinkers in high total dissolved solids fracturing fluids without the pH destabilization problems encountered with the prior art.