Cesium Formate Brine pH Control for Hydrogel Delay
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Solution Overview
Problem
Xanthan-viscosified cesium formate brines tend to form solid or solid-like hydrogels over time, making them difficult to pump and use in well treatment operations such as gravel packing, due to their high viscosity.
Innovation Solution
Lowering the pH of cesium formate brine solutions containing xanthan gum helps prevent solid-like hydrogel formation, allowing for the creation of pourable gels that can be easily pumped, by mixing xanthan polymer with cesium formate brine and adjusting the pH to specific levels, typically below 11.4, and adding acid to maintain pumpability during treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If xanthan polymer is mixed in cesium formate brine to increase viscosity, then the brine can be used for gravel packing and well treatment operations, but the brine forms solid or solid-like hydrogels over time, making it difficult to pump
Solution Approach 1:
The patent applies parameter changes by adjusting the pH of the cesium formate brine to below 11.4 (preferably between 7-11) to prevent the formation of solid hydrogels. This pH adjustment maintains the fluid's viscosity for gravel packing while preventing gelation that would compromise pumpability, thus resolving the contradiction between maintaining strength and ensuring ease of operation
Solution Approach 2:
The patent applies preliminary action by adding acid to lower the pH of the brine before mixing in the xanthan polymer. This pre-adjustment of pH prevents hydrogel formation from occurring during storage or transport, ensuring the fluid remains pumpable throughout the treatment operation while still providing the necessary viscosity
2Strength
If xanthan-viscosified cesium formate brine is prepared for gravel packing, then the fluid has sufficient viscosity for the treatment, but the fluid takes too long to remain pourable due to hydrogel formation
Solution Approach 1:
The patent changes the pH parameter of the brine to below 11.4, which fundamentally alters the chemical environment to prevent xanthan polymer from forming solid hydrogels. This parameter change extends the time window during which the fluid remains pourable and pumpable while maintaining adequate viscosity for gravel packing operations
3Quantity of substance
If high density brine (at least 1.44 g/cm³) is used for subterranean treatment, then the brine has sufficient density for the application, but adding xanthan polymer causes rapid hydrogel formation that compromises fluidity
Solution Approach 1:
The patent applies parameter changes by controlling the pH of the high density cesium formate brine to below 11.4. This pH control prevents the xanthan polymer from undergoing the chemical changes that lead to solid hydrogel formation, thereby maintaining both the required high density (at least 1.44 g/cm³) and the stability of the fluid composition over time
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 method effectively delays the onset of hydrogel formation, ensuring the fluid remains pourable for extended periods, facilitating its use in subterranean treatments like gravel packing and hydraulic fracturing by maintaining fluidity and pumpability.
Implementation Method 1
hydrating the xanthan polymer
Implementation Method 2
Xanthan gum is often used to viscosify brines to prepare gravel packing fluids
Implementation Method 3
xanthan-viscosified cesium formate brines can form solid or solid-like hydrogels over a period of time
Implementation Method 4
lowering the pH of the brine
Implementation Method 5
lowering the pH comprises adding acid to the brine, e.g., an organic acid such as formic acid, or a mineral acid
Data Source
AI summary
A method of treating a subterranean formation with a xanthan-viscosified cesium formate brine wherein the pH and/or another characteristic selected from density, xanthan loading, sodium formate loading, potassium formate loading and combinations thereof are modified to delay solid hydrogel formation and maintain pumpability. Also disclosed is a method of delaying onset of solid hydrogel formation, in a gel comprising cesium formate brine viscosified with xanthan polymer, comprises introducing acid into the brine in an amount effective for a pH from 7 to 11, wherein the acid introduction is before, during or after xanthan viscosification and prior to hydrogel formation, wherein the hydrogel formation in the acidified gel occurs at a later time relative to the same gel at a natural pH.