Viscoelastic Surfactant for High-Temperature Self-Diverting Acid
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current viscoelastic surfactant (VES) systems for self-diverting acids are not stable under high temperatures, leading to reduced viscosity and ineffective acid-rock reaction rate control, which limits their application in high-temperature oil and gas reservoirs.
Innovation Solution
A new VES with a specific structural formula, involving a fatty acid and organic amine reaction followed by metal hydride treatment, is developed to create an ultra-long-chain surfactant that maintains stability and viscosity in high-temperature environments, allowing for effective acid solution thickening and diversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional VES systems are used in high-temperature reservoirs, then the acid solution can divert to low-permeability zones, but the VES decomposes at temperatures above 120°C causing viscosity to drop and losing diverting capability
Solution Approach 1:
The patent modifies the molecular structure parameters of VES by introducing aromatic rings, heteroatoms (N, O, S), and specific functional groups to enhance thermal stability. The structural formula shows optimized hydrophobic and hydrophilic segment ratios that maintain viscosity at 150°C while preserving diverting functionality.
Solution Approach 2:
The invention creates a composite surfactant structure combining rigid aromatic cores with flexible alkyl chains and polar head groups. This composite architecture provides both thermal resistance and surface-active properties, enabling the VES to withstand high temperatures while maintaining diverting capability.
2Strength
If acid concentration is increased to enhance etching capability, then the acid-rock reaction rate increases, but the effective acidification distance decreases due to rapid consumption
Solution Approach 1:
The VES system provides self-service by automatically adjusting its viscosity in response to pH changes during acid-rock reaction. As HCl is consumed and pH rises, the VES molecules self-associate to increase viscosity, which in turn slows further acid consumption and extends the acidification distance without requiring external control.
Solution Approach 2:
The patent employs a dynamic viscosity system where the VES concentration and molecular conformation change continuously during the acidizing process. The viscosity increases as the acid reaction progresses, creating a time-dependent flow behavior that optimizes both initial penetration and subsequent diverting.
3Reliability
If VES concentration is increased to maintain viscosity at high temperature, then thermal stability improves, but the cost and potential reservoir damage from excessive viscosity increase
Solution Approach 1:
The patent optimizes the molecular weight and structural parameters of VES to achieve maximum thermal stability at minimum concentration. The specific structural formula with optimized chain lengths and functional group distribution allows effective diverting at 0.1-5% concentration rather than requiring higher dosages.
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 new VES system achieves stable viscosity greater than 80 mPa·s at 150°C, slows acid-rock reactions, and ensures uniform acidification, reducing operational costs and environmental impact.
Implementation Method 1
viscoelastic surfactant (VES) as thickeners for conventional acid system
Implementation Method 2
the diffusion of H+ to the rock surface is slowed down
Implementation Method 3
metal ions (Ca2+) are continuously produced, which further increases the viscosity of the acid system
Implementation Method 4
the hydrophobic cores of the wormlike micelles in the viscoelastic surfactant solution will be destroyed
Implementation Method 5
transform into spherical micelles, which results in the rapid reduction of the viscosity of the system
Data Source
AI summary
A viscoelastic surfactant (VES) for a self-diverting acid under high temperature has a structural formula shown as formula (I), wherein, n is saturated hydrocarbon with 2 to 8 carbon atoms; R1 is saturated or unsaturated hydrocarbon with 18 to 28 carbon atoms; R2 and R3 are independently methyl, ethyl or hydrogen, and R2 and R3 can be the same or different; and X− is any one of Cl−, Br−, CO32−, SO42−, HCOO− and CH3COO−. The method for preparing the surfactant includes subjecting a fatty acid and an organic amine to acid-amine condensation to obtain an intermediate. The intermediate reacts with a metal hydride to obtain a fatty amine. Then, an acid solution is used to protonate the fatty amine to obtain an ultra-long-chain viscoelastic cationic surfactant. The present invention also provides use of the surfactant as a thickener for a self-diverting acid.