Crosslinked Fluids for Viscosity Stability
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Solution Overview
Problem
Conventional treatment fluids used in subterranean operations, such as hydraulic fracturing and sand control, face challenges in maintaining viscosity stability, particularly at higher temperatures, where mixtures of xanthan and guar gum become unstable, leading to over-viscosification and undesirable rheological properties.
Innovation Solution
The use of treatment fluids comprising an aqueous base fluid, a crosslinking agent, and a gelling agent that includes a crosslinkable polymer and a biopolymer with a backbone comprising glucose and pyranose-type monosaccharide units, such as diutan, which provides enhanced viscoelastic properties and improved proppant transport without syneresis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If xanthan and guar gum are used as gelling agents in treatment fluids, then viscosity is increased for particulate transport, but the mixture becomes unstable at higher temperatures leading to over-viscosification and syneresis
Solution Approach 1:
The patent changes the chemical parameters of the gelling agent by using hydrolyzed polyacrylamide with specific degrees of hydrolysis (30-80%) instead of conventional xanthan and guar gum mixtures. This parameter change enables the fluid to maintain stable viscosity across a broader temperature range (up to 200°F) without over-viscosification or syneresis, while still providing adequate viscosity for particulate transport
Solution Approach 2:
The patent creates a composite gelling system by combining hydrolyzed polyacrylamide with crosslinking agents (such as borax, zinc chloride, or calcium chloride) to form a crosslinked gel structure. This composite approach provides temperature-stable viscosity while avoiding the harmful effects of conventional polymer mixtures, achieving both viscosity stability and resistance to over-viscosification
2Productivity
If crosslinking agents are added to increase viscosity and improve proppant transport, then proppant transport capability is enhanced, but the fluid may become too viscous and difficult to break for recovery
Solution Approach 1:
The patent introduces an intermediary substance (starch or cellulose) that acts as a breaker for the crosslinked gel structure. This intermediary allows the crosslinked network to be selectively broken down after completing its proppant transport function, enabling the fluid to be easily recovered from the formation without requiring excessive breaking agents
Solution Approach 2:
The patent creates a dynamic gel system where the crosslinked structure can adapt its properties based on environmental conditions. The gel maintains its crosslinked structure at downhole temperatures to provide proppant transport capability, but can be broken down when exposed to specific breakers (starch, cellulose, or enzymes) that alter the crosslinking chemistry, thus providing both high productivity and ease of operation
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 achieves stable viscosity and improved proppant transport with extended relaxation times, reducing syneresis and maintaining effective fluid properties across varying conditions, including higher temperatures.
Implementation Method 1
a gelling agent that includes a crosslinkable polymer and a biopolymer... and a crosslinking agent
Implementation Method 2
a gelling agent that includes a crosslinkable polymer and a biopolymer wherein the biopolymer provides enhanced viscoelastic properties
Implementation Method 3
a biopolymer wherein the biopolymer provides enhanced viscoelastic properties... stable viscosity... maintaining effective fluid properties across varying conditions, including higher temperatures
Data Source
AI summary
Treatment fluids comprising gelling agents that comprise crosslinkable polymers and certain biopolymers, and methods of use in subterranean operations, are provided. In one embodiment, the present invention provides a treatment fluid comprising: an aqueous base fluid; a crosslinking agent; and a gelling agent comprising a polymer that is a crosslinkable polymer, and a polymer that is a biopolymer wherein a molecule of the biopolymer (1) consists only of glucose, or (2) has a backbone comprising one or more units that comprise at least (a) one glucose unit and (b) one linear or cyclic pyranose-type monosaccharide unit, wherein (a) and (b) have different molecular structures.