Viscous Wellbore Fluids Using Cucurbituril 8 Inclusion Complexes
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Solution Overview
Problem
Current wellbore fluids used in hydrocarbon recovery and fracturing lack efficient viscosity control mechanisms, particularly in hydraulic fracturing, where viscosity needs to be reduced after fracture formation to facilitate fluid removal and prevent filtercake formation at the fracture boundary.
Innovation Solution
A wellbore fluid comprising a viscosifying polymer formed through the inclusion complex of cucurbituril 8 (CB[8]) with guest molecules, which self-assemble into longer, cross-linked chains upon reaching subterranean temperatures, providing reversible viscosity enhancement and reduction capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a viscosifying polymer is used to enhance fluid viscosity for proppant transport, then proppant transport efficiency is improved, but fluid removal difficulty increases due to high viscosity after fracture formation
Solution Approach 1:
The patent applies dynamic viscosity control by using a polymer that changes its viscosity state over time. The polymer starts with high viscosity to transport proppants effectively, then gradually degrades to reduce viscosity for easy fluid removal. This temporal dynamic transformation resolves the contradiction between needing high viscosity during injection and low viscosity during production.
Solution Approach 2:
The patent changes the molecular weight parameter of the polymer over time through controlled degradation. The polymer begins with high molecular weight for viscosity and proppant transport, then degrades to lower molecular weight fragments that provide reduced viscosity and improved fluid mobility while maintaining proppant suspension capabilities.
2Strength
If polymer cross-linking is used to increase viscosity for fracture proppant support, then fracture proppant support is improved, but filtercake formation increases at the fracture boundary
Solution Approach 1:
The patent controls the molecular weight parameter of the polymer to optimize performance. By using moderate molecular weight polymers rather than high molecular weight cross-linked polymers, the fluid provides sufficient viscosity for proppant support while reducing excessive polymer concentration at the fracture boundary, thereby minimizing filtercake formation.
3Temperature
If high molecular weight polymer is used to provide viscosity for fluid transport, then viscosity is improved, but polymer degradation time increases extending fluid retention in wellbore
Solution Approach 1:
The patent optimizes the molecular weight parameter to achieve balanced performance. Rather than using very high molecular weight polymers that maintain viscosity too long, the patent uses moderately high molecular weight polymers that provide sufficient viscosity for transport but degrade within an optimal time frame to allow timely fluid removal and wellbore clearance.
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 enables controlled viscosity adjustment, allowing for effective transport of proppants and subsequent reduction in viscosity for easy fluid removal, while maintaining viscosity at the fracture site to prevent closure, thus optimizing hydraulic fracturing efficiency and reducing pumping costs.
Implementation Method 1
portions of the polymer are connected through formation of an inclusion complex involving cucurbituril 8
Implementation Method 2
effective transport of proppants
Data Source
AI summary
A wellbore fluid contains a viscosifying polymer in which portions of the polymer are connected through formation of an inclusion complex involving cucurbituril 8 (i.e. CB[8]) as host molecule. The fluid contains guest molecules with first and second guest groups covalently attached wherein at least one of the guest molecules comprises a polymer chain. The CB[8] host and the guest molecules attach together through reception of first and second guest groups within CB[8] host cavities, thereby connecting polymer chains together as a larger, supramolecular polymer and enhancing viscosity of the fluid. Polymer molecules may be synthetic polymers and guest groups may be attached to monomers before polymerization. Alternatively guest groups may be attached to existing polymers which may be polysaccharide.