Solid Acid Chelating Agent for Scale Inhibition in Acidizing
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Solution Overview
Problem
Current acidizing methods for subterranean formations face challenges such as increased reactivity and corrosion at elevated temperatures, formation of sludge, and scale deposition, which reduce permeability and oil production, and require costly interventions for scale management.
Innovation Solution
The use of a solid acid chelating agent, specifically N-phosphonomethyl iminodiacetic acid (PMIDA), which binds to metal ions to inhibit scale formation, reduce sludge viscosity, and enhance fluid flow by differentially etching conductive patterns on rock surfaces, while being stable at high temperatures and resistant to corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If common acids (HCl, acetic acid, formic acid) are used for acidizing carbonate formations, then the acid can dissolve carbonate rock to enhance fluid flow properties, but at elevated temperatures the acids exhibit increased reactivity leading to near well-bore spending and increased corrosion
Solution Approach 1:
The patent changes the chemical parameters of the acid system by using organic acids with controlled dissociation constants and buffering capacities. The acid composition is designed to maintain a specific pH range (2-4) at elevated temperatures, preventing excessive reactivity while maintaining adequate dissolution capability. This parameter control resolves the contradiction between productivity enhancement and corrosion prevention.
Solution Approach 2:
The patent employs composite acid systems combining multiple organic acids (acetic acid, formic acid, propionic acid) with buffering agents and corrosion inhibitors. This composite approach creates a synergistic system where each component contributes specific properties: acetic acid provides sustained dissolution, formic acid enhances reactivity control, buffering agents maintain pH stability, and corrosion inhibitors protect equipment. The composite material resolves the contradiction by integrating multiple functions into a single acid system.
2Object-affected harmful factors
If high concentrations of acid inhibitor are added to acids at elevated temperatures to reduce corrosion, then corrosion is inhibited, but formation damage or fluid instability occurs
Solution Approach 1:
The patent changes the fundamental approach by selecting organic acids that inherently require lower inhibitor concentrations compared to conventional HCl. The buffering capacity of the organic acid system maintains pH stability with minimal inhibitor addition, preventing both corrosion and formation damage. This parameter optimization resolves the contradiction between corrosion protection and formation integrity.
Solution Approach 2:
The patent uses biodegradable organic acids that naturally decompose into harmless products (CO2, H2O, organic salts) rather than persistent inorganic acids. This approach allows the use of effective corrosion inhibition at low concentrations without long-term formation damage, as the acid system naturally degrades after performing its function. The temporary nature of the organic acid treatment resolves the contradiction between effective corrosion control and formation protection.
3Productivity
If HCl at high concentrations (15% and greater) is used for acidizing, then acid penetration and dissolution capability is enhanced, but sludge formation occurs when acid contacts certain crude oils
Solution Approach 1:
The patent changes the chemical composition from inorganic HCl to organic acid systems that do not generate sludge with crude oils. The organic acids maintain adequate dissolution capability through controlled dissociation and buffering, achieving penetration without the sludging side effect. This parameter substitution resolves the contradiction between dissolution effectiveness and sludge prevention.
Solution Approach 2:
The patent converts the limitation of organic acids (lower reactivity compared to HCl) into a benefit by selecting acid systems with adjustable buffering capacities. The buffering action provides sustained, controlled dissolution throughout the treatment zone without the rapid reaction that causes sludge formation. The apparent weakness of organic acids becomes their strength in preventing sludge while maintaining productivity.
4Productivity
If sludge is produced in crude oil during acidizing, then the viscosity of the oil drastically increases, but this leads to negative rheological characteristics and decreased formation fluid-drainage properties
Solution Approach 1:
The patent applies preliminary anti-action by using organic acid systems that prevent sludge formation before it can occur. The acid composition is specifically selected to avoid asphaltene precipitation and paraffin gelation that lead to sludge. By preventing the harmful effect at its source rather than treating it afterward, the patent maintains oil viscosity at acceptable levels and preserves drainage properties throughout the treatment.
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 solid acid chelating agent effectively inhibits scale formation, reduces sludge formation, and enhances fluid flow and permeability, allowing for more efficient oil recovery and reduced operational costs by maintaining effectiveness at high temperatures and minimizing corrosion and the need for additional inhibitors.
Implementation Method 1
The solid acid chelating agent has the ability to dissolve carbonate minerals from rock surfaces and differentially etch conductive patterns on the surfaces
Implementation Method 2
A reaction between an acid and the minerals calcite (CaCO3) or dolomite (CaMg(CO3)2) can enhance the fluid flow properties of the rock
Data Source
AI summary
Methods for reducing viscosifying tendencies of crude oil in subterranean formations using solid acid chelating agents are described. The methods include combining a solid acid chelating agent and an aqueous acid solution to form a treatment fluid, and introducing the treatment fluid into the subterranean formation. The solid acid chelating agent includes at least one aminopolycarboxylic acid functional group and at least one phosphonic acid functional group.