Crosslinked Guar Fluid Loss Pill for High-Temperature Stability
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Solution Overview
Problem
Conventional fluid loss pills degrade quickly at high temperatures and high pressures, leading to reduced viscosity and formation damage in subterranean formations, especially when using high-density brines like calcium and zinc salts.
Innovation Solution
A fluid loss pill comprising a brine and a crosslinked polymer of underivatized guar or derivatized guar with a puffed boron or ulexite crosslinking agent, along with glycerol and a copolymer of sulfonated acrylamide and vinyl lactam, which maintains high viscosity and stability even at temperatures above 275°F, reducing fluid loss and formation impairment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cellulosic polymers (HEC) are used in fluid loss pills, then the pills can be formulated with high-density brines for deep well applications, but the polymers degrade quickly at high temperatures above 250°F, causing reduced viscosity and formation damage
Solution Approach 1:
The patent changes the polymer chemistry from cellulosic derivatives to guar-based polymers, which have different thermal stability characteristics. This parameter change in polymer composition allows the fluid to maintain viscosity at temperatures above 250°F where conventional HEC degrades. The crosslinking mechanism using boron or ulexite with guar hydroxyl groups creates a thermally stable gel structure that preserves viscosity under high-temperature downhole conditions.
Solution Approach 2:
The invention creates a composite system combining guar polymer, crosslinking agent (boron or ulexite), and high-density brine. This composite material approach integrates multiple components that work synergistically: the guar polymer provides the base structure, the crosslinking agent creates thermal stability through crosslinked networks, and the brine provides density for deep well applications. This composite structure maintains both the density requirement and temperature stability simultaneously.
2Temperature
If high-density brines containing divalent salts (calcium, zinc) are used, then the fluid can handle high temperature and pressure conditions in deep wells, but calcium and zinc cations form stable acid-insoluble compounds that damage formation permeability when the polymer degrades
Solution Approach 1:
The patent changes the polymer chemistry from cellulosic to guar-based, which fundamentally alters the degradation behavior. Guar polymers with crosslinking agents maintain structural integrity at high temperatures, preventing the release of calcium and zinc cations that would otherwise form harmful precipitates. This parameter change in polymer selection eliminates the source of cation release while preserving the ability to use high-density brines for high-temperature applications.
Solution Approach 2:
The invention converts the potential harm of divalent cations into a benefit by using crosslinked guar polymers that are stable in their presence. Instead of the cations causing degradation and precipitate formation (as with HEC), the crosslinked guar structure resists degradation, and the cations remain in solution, maintaining fluid density without forming formation-damaging compounds. The system transforms a harmful interaction into a stable, beneficial configuration.
3Ease of operation
If conventional HEC-based fluid loss pills are used, then they can be pumped into wells, but they become unstable and lose viscosity rapidly in environments above 250°F, resulting in fluid leak-off into the formation
Solution Approach 1:
The patent changes the polymer from HEC to crosslinked guar, which has superior thermal stability. This parameter change maintains viscosity stability at temperatures above 250°F while preserving pumpability. The crosslinked guar polymer solution remains stable during pumping and injection, then maintains its viscosity and sealing capability at the high-temperature downhole environment where conventional HEC would degrade and leak.
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 fluid loss pill exhibits enhanced stability and viscosity, minimizing fluid loss and formation damage, and can be stored for later use, maintaining effectiveness for extended periods in high-temperature wells.
Implementation Method 1
a crosslinked polymer of underivatized guar or a derivatized guar and a puffed boron or ulexite crosslinking agent
Implementation Method 2
The viscosity of the fluid loss pill is increased under in-situ operating conditions at a targeted location within the well
Implementation Method 3
The viscosity of the fluid loss pill is increased under in-situ operating conditions at a targeted location within the well
Data Source
AI summary
A fluid loss pill containing a brine and a crosslinked polymer of underivatized guar or a derivatized guar and puffed boron or ulexite crosslinking agent. The brine may be a heavy brine having a density greater than 11.0 ppg.