Time-Release Metal-Complexing Agent for Slick-Water Fracturing
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Solution Overview
Problem
The effectiveness of slick-water fracturing operations in hydrocarbon-bearing shales is reduced due to interactions between metal ions in the shale and friction-reducing polymers, leading to decreased performance and difficulties in removing the polymer from the fracture and wellbore after completion.
Innovation Solution
A time-release form of a metal-complexing agent, such as citric acid or EDTA, is encapsulated with a hydrophobic coating and a porous cross-linked hydrophilic polymer to prevent premature dissolution, ensuring it binds with metal ions in the shale only when needed, thereby maintaining the polymer's friction-reducing effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal-complexing agent is added to the fracturing fluid to bind with metal ions in the shale, then the polymer's friction-reducing effectiveness is improved, but the metal-complexing agent dissolves prematurely and loses effectiveness before reaching the target formation
Solution Approach 1:
The metal-complexing agent is encapsulated in a coating that prevents premature dissolution during pumping and injection. The coating is designed to break down or become permeable only after the fluid reaches the target formation, allowing the metal-complexing agent to become active at the precise moment and location needed to bind with metal ions and protect the polymer
Solution Approach 2:
The encapsulating coating acts as an intermediary barrier between the metal-complexing agent and the surrounding fracturing fluid. This intermediate layer protects the metal-complexing agent from premature interaction with other fluid components while allowing controlled release at the destination, ensuring the agent remains stable during transport but active when needed
2Reliability
If the metal-complexing agent is released early in the wellbore, then it can bind with metal ions, but it interacts with the polymer and reduces its friction-reducing capabilities before the fluid reaches the formation
Solution Approach 1:
The encapsulation system ensures that the metal-complexing agent is delivered to the target formation in an inactive, protected state. Only after reaching the formation does the coating break down, allowing the agent to become active and bind with metal ions. This preliminary protection prevents any premature interaction with the polymer that would reduce pumping efficiency
Solution Approach 2:
The fracturing fluid system is segmented into distinct functional zones: the polymer provides friction reduction during pumping, while the encapsulated metal-complexing agent remains isolated and inactive during transport. The segmentation is maintained through the encapsulation barrier, allowing each component to perform its primary function without interference until the fluid reaches the formation
3Reliability
If higher concentrations of metal-complexing agent are used to ensure sufficient binding with metal ions, then the polymer protection is improved, but the cost of the fracturing treatment increases
Solution Approach 1:
The encapsulation technology enables precise delivery of the metal-complexing agent directly to the target formation, preventing loss during transport. This ensures that nearly 100% of the added agent reaches where it is needed, allowing lower overall concentrations to achieve the same protective effect compared to unencapsulated agents that would dissolve or degrade before reaching the formation
Solution Approach 2:
The encapsulated metal-complexing agent is designed to automatically release its contents in response to specific conditions at the target formation, such as pH changes or mechanical stress from fracture propagation. This self-activating mechanism ensures efficient utilization of the agent, reducing the need for excessive concentrations to achieve adequate metal ion binding
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 use of a time-release metal-complexing agent improves the performance of slick-water fracturing by preventing undesirable interactions with metal ions, allowing the polymer to maintain its friction-reducing capabilities and facilitating easier removal, thus enhancing the fracturing process and subsequent oil and gas recovery.
Implementation Method 1
A time-release form of a metal-complexing agent, such as citric acid or EDTA, is encapsulated with a hydrophobic coating
Implementation Method 2
A time-release form of a metal-complexing agent, such as citric acid or EDTA, is encapsulated with a hydrophobic coating and a porous cross-linked hydrophilic polymer
Implementation Method 3
a time-released form of a metal-complexing agent... ensuring it binds with metal ions in the shale
Data Source
AI summary
In a slick-water fracturing operation, a composition is used to prevent the interaction between a polymer in a water-based fracturing fluid and naturally-occurring metal ions. The composition includes a metal-complexing agent, such as a chelating agent. The chelating agent can also be biodegradable and is citric acid in embodiments. The metal-complexing agent can be coated with one or two coatings to create a time-released form. The time -released form prevents loss of the agent prior to delivery at the shale.