Borate Crosslinking Fluids for Fracturing
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Solution Overview
Problem
Current methods for controlling the gelation rate of borate-based aqueous subterranean treating fluids, particularly at high temperatures and varying pH levels, are limited in precision and effectiveness, leading to inadequate rheological stability and potential damage to proppant packs during hydraulic fracturing operations.
Innovation Solution
The development of novel compositions comprising a crosslinkable organic polymer and a sparingly-soluble borate crosslinking agent, combined with a crosslink modifier such as salts, acids, or alkaline/acidic chemicals, which adjust the gelation rate without altering the final pH or system characteristics, allowing for controlled crosslinking in a wide range of subterranean environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If crosslinking time delay agents are used to control gelation rate, then the fracturing fluid can be pumped down hole before crosslinking occurs, but the permeability of the proppant pack is significantly damaged (greater than 80%)
Solution Approach 1:
The invention changes the chemical parameters of the crosslinking system by using borate crosslinking agents with pKa values between 8.5 and 10.5 in combination with pH buffers to maintain pH between 9.0 and 11.0. This parameter control enables delayed crosslinking without the need for traditional delay agents that cause proppant pack damage, achieving both extended pumpable time and preserved formation permeability.
Solution Approach 2:
The invention introduces pH buffers as intermediary substances that mediate between the borate crosslinking agent and the polysaccharide fluid. The buffers control the protonation state of the borate, creating a controlled release mechanism that delays crosslinking until the fluid reaches the desired location, while avoiding the harmful effects of conventional delay agents on proppant pack permeability.
2Strength
If traditional crosslinking agents are used to increase viscosity and proppant-transport capabilities, then the fluid rheological properties are improved, but the thermal stability above 200° F. is insufficient
Solution Approach 1:
The invention creates a composite crosslinking system combining borate crosslinking agents with specific pKa values (8.5-10.5) and pH buffers working together. This composite approach provides both the desired viscosity enhancement for proppant transport and thermal stability at temperatures above 200° F., overcoming the limitations of traditional single-agent systems.
Solution Approach 2:
The invention exploits the temperature-dependent dissociation behavior of borates with pKa values between 8.5 and 10.5. At elevated temperatures above 200° F., the shifted equilibrium maintains effective crosslinking density, preserving viscosity and proppant-transport capabilities where traditional crosslinking agents fail.
3Ease of operation
If crosslinking reactions are delayed to allow fluid pumping, then operational flexibility is improved, but the gelation rate control precision is insufficient with existing methods
Solution Approach 1:
The invention creates a feedback-controlled crosslinking system where pH buffers continuously regulate the borate crosslinking agent activity. The buffer system responds to changes in pH and temperature, automatically adjusting the crosslinking rate to maintain precision control throughout the operational timeline, from pumping through to gelation.
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
This approach enables precise control over the crosslinking reaction rates, enhancing the thermal and pH stability of fracturing fluids, reducing equipment requirements, and minimizing damage to proppant packs, thereby improving the efficiency and safety of hydrocarbon recovery operations.
Implementation Method 1
a crosslinking additive comprising a borate-containing crosslinking agent... capable of controlling the rate at which the crosslinking additive promotes the gelation of the organic polymer
Implementation Method 2
a crosslink modifier composition capable of controlling the rate at which the crosslinking additive promotes the gelation of the organic polymer
Data Source
AI summary
Treating fluid compositions for use in hydrocarbon recovery operations from subterranean formations are described, as well as methods for their preparation and use. In particular, treating fluid compositions are described which comprise a liquid, a crosslinkable organic polymer material that is at least partially soluble in the liquid, a crosslinking agent that is capable of increasing the viscosity of the treating fluid by crosslinking the organic polymer material in the liquid, and a crosslinking modifier additive which can delay or accelerate the crosslinking of the treating fluid composition. Such compositions may be used in a variety of hydrocarbon recovery operations including fracturing operations, drilling operations, gravel packing operations, water control operations, and the like.