Polymer-Coated Proppant Silane Bonding
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Solution Overview
Problem
Existing proppant coatings for hydraulic well fracturing face challenges in forming interparticle bonds effectively across a wide range of downhole temperatures and pressures, particularly due to premature curing at elevated temperatures and compatibility issues with fracturing fluids, which affects conductivity and flowback control.
Innovation Solution
A polymer-coated proppant with an outer layer comprising an organofunctional silane coupling agent that reacts to form enhanced interparticle bonding at downhole conditions, using a combination of inner and outer polymer layers and specific silane functionalities for improved thermal stability and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If partially cured phenolic coating is used to enable interparticle bonding in low temperature wells, then bonding capability is improved, but premature curing occurs at elevated temperatures before introduction into fractured strata
Solution Approach 1:
The patent changes the chemical parameters of the coating by using a two-component system (isocyanate component and polyol component) instead of traditional phenolic resin. This allows the coating to remain stable at elevated temperatures during storage and transport, then cure effectively at downhole temperatures to form interparticle bonds. The specific parameter change is the glass transition temperature (Tg) of the coating, which is adjusted to be above the storage temperature but below the downhole temperature, preventing premature curing while enabling bonding in situ.
Solution Approach 2:
The patent employs a composite coating system consisting of multiple components: an isocyanate-functional component, a polyol component, and optionally a catalyst. This composite material approach allows each component to contribute specific properties - the isocyanate provides reactivity for bonding, the polyol provides thermal stability, and the catalyst controls the curing rate. The composite nature of the coating resolves the contradiction between stability during storage and reactivity for bonding by combining materials with complementary properties.
2Productivity
If activator is added to partially cured phenolic proppant to promote consolidation and interparticle bonding, then bonding speed is improved, but compatibility issues with fracturing and breaker fluids arise
Solution Approach 1:
The patent extracts and eliminates the need for external activators by incorporating all necessary curing components directly into the coating system. The isocyanate and polyol components are applied to the proppant surface, and the curing reaction is initiated by downhole conditions (temperature and pressure) rather than requiring additional chemical activators. This removes the source of compatibility problems with fracturing and breaker fluids while maintaining rapid bonding capability.
Solution Approach 2:
The coating system is designed to self-cure under downhole conditions without requiring external activators or additives. The isocyanate and polyol components react automatically when exposed to downhole temperature and pressure, forming interparticle bonds autonomously. This self-service approach eliminates the need for additional chemicals that could cause compatibility issues, while the downhole environment itself provides the energy needed for the bonding reaction.
3Temperature
If precured phenolic coating is used for high temperature wells, then thermal stability is improved, but interparticle bonding capability is reduced
Solution Approach 1:
The patent introduces dynamic control of the coating's curing state through the use of a two-component system with a specific glass transition temperature (Tg). The coating transitions from a flexible, uncured state during storage and transport to a rigid, bonded state under downhole conditions. This dynamic behavior allows the coating to maintain thermal stability at high temperatures while still enabling interparticle bonding, as the curing reaction is triggered by the downhole temperature and pressure environment rather than occurring prematurely during handling.
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 significantly enhances interparticle bond strength across various temperature conditions, maintaining proppant conductivity and reducing flowback, while avoiding the need for external activators and improving compatibility with fracturing fluids.
Implementation Method 1
the outer layer of the proppants are mutually reactive and form enhanced interparticle bonding at the temperatures and crack closure pressures found downhole in fractured strata
Implementation Method 2
using a combination of inner and outer polymer layers and specific silane functionalities for improved thermal stability and adhesion
Implementation Method 3
A polymer-coated proppant with an outer layer comprising an organofunctional silane coupling agent that reacts to form enhanced interparticle bonding
Data Source
AI summary
Polymer-coated proppants for hydraulic fracturing of oil and gas wells have an outer layer portion that comprises an organofunctional coupling agent, preferably an organofunctional silane coupling agent. The use of an organofunctional silane coupling agent in the outer layer portion of the proppant coating is preferably chosen to expose functionalities that will be reactive towards similar functionalities of adjacent and similarly coated proppants so that, when introduced downhole, these proppants form interparticle bonds at the temperatures and crack closure pressures found downhole in fractured strata. Such enhanced interparticle bonding helps keep the proppant in the fracture and maintains conductivity with reduced flowback. The invention also helps proppants designed for low temperature well to bond more firmly and allows proppants designed for high temperature wells to bond well even at lower downhole temperatures, thereby extending their useful range.