Reverse Emulsion Fracturing Fluid for High Salinity
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Solution Overview
Problem
Current friction reducers for hydraulic fracturing fluids are ineffective in high salinity conditions, particularly with high levels of divalent salts, which limits their ability to reduce friction and enhance permeability in unconventional oil and gas reservoirs.
Innovation Solution
A water-in-oil reverse emulsion comprising a cationic polymer with specific molecular mass and monomer composition, along with a reversing agent and emulsifying agent, is used to create a fracturing fluid that effectively reduces friction in high salinity environments by optimizing the weight ratio of reversing to emulsifying agents and incorporating a water-soluble cationic copolymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional friction reducers are used in high salinity fracturing fluids, then friction reduction is effective in low salinity conditions, but the friction reduction performance deteriorates significantly in high salinity conditions with high levels of divalent salts
Solution Approach 1:
The patent changes the chemical parameters of the polymer by using a cationic copolymer with specific monomer composition (15-30 mol% cationic monomers with positive charges) and high molecular weight (10-50 million Daltons). The charge density and molecular structure parameters are optimized to maintain effectiveness in high salinity environments where conventional polymers fail.
Solution Approach 2:
The invention uses a composite copolymer structure combining hydrophobic monomers (for friction reduction) and cationic monomers (for salt tolerance). This composite material approach creates a polymer that simultaneously provides friction reduction performance and adaptability to high salinity conditions with divalent salts.
2Loss of energy
If water-soluble polymers are used to reduce friction, then friction reduction is achieved in low salinity conditions, but the polymer becomes ineffective and precipitates in very high salinity conditions
Solution Approach 1:
The patent transforms the polymer from water-soluble to oil-soluble by incorporating hydrophobic monomers and structuring the polymer as a reverse emulsion. The cationic copolymer is dispersed in oil phase rather than water phase, fundamentally changing the solubility parameter to prevent precipitation in high salinity brines while maintaining friction reduction capability.
Solution Approach 2:
Instead of using water-soluble polymers that fail in high salinity, the invention inverts the approach by using oil-soluble cationic copolymers in a reverse emulsion system. The polymer is dissolved in oil phase and then emulsified, reversing the conventional water-based polymer approach to achieve stability in high salinity conditions.
3Reliability
If reverse emulsion is used with high ratio of reversing agent to emulsifying agent, then friction reduction performance is improved in high salinity conditions, but the emulsion stability and processing complexity increase
Solution Approach 1:
The patent optimizes the weight ratio parameter of reversing agent to emulsifying agent to be greater than 1.5 (preferably 2.0-3.0). This parameter change in the emulsion formulation achieves the right balance between friction reduction performance in high salinity and adequate emulsion stability, avoiding excessive complexity while maintaining effectiveness.
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 provides superior friction reduction performance even in very high salinity conditions, enhancing the efficiency of hydraulic fracturing operations by maintaining low viscosity during injection and high viscosity to suspend propping agents, thereby reducing hydraulic power requirements and improving permeability.
Implementation Method 1
polymers known as friction reducers are used. By using such polymers, pressure losses due to internal friction in the fluid can be reduced by up to 70%
Implementation Method 2
maintaining low viscosity during injection and high viscosity to suspend propping agents
Implementation Method 3
a water-in-oil reverse emulsion comprising an oil, water, at least one water-soluble cationic copolymer, at least one reversing agent and at least one emulsifying agent
Implementation Method 4
the reverse emulsion is reversed, so that the polymer contained in the water phase of the reverse emulsion is released
Implementation Method 5
at least one water-soluble cationic copolymer... stable under very high salinity conditions... containing between 18 and 32 mole % of cationic monomers
Data Source
AI summary
The present application relates to a water-in-oil reverse emulsion comprisingan oil;water;at least one water-soluble cationic copolymer with an average molar mass of more than 3 million daltons, containing between 18 and 32 mole % of cationic monomers and 68 and 82 mole of nonionic monomers;at least one reversing agent and at least one emulsifying agent, the weight ratio R of the total amount of reversing agent to the total amount of emulsifying agent being greater than 1.8,the reversing agent being selected from an ethoxylated nonylphenol, preferably having between 4 and 10 ethoxylations; an ethoxylated/propoxylated alcohol, preferably having ethoxylations/propoxylations so as to have a total carbon number between C12 and C25, an ethoxylated tridecyl alcohol and an ethoxylated/propoxylated fatty alcohol.the emulsifying agent being selected from sorbitan monooleate, polyethoxylated sorbitan esters or diethanolamide of tall oil fatty acids,and its use in hydraulic fracturing.