GLDA MGDA Stimulation Fluids for Carbonate Wormhole Formation
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Solution Overview
Problem
Current matrix acidizing techniques using hydrochloric acid in carbonate formations face limitations such as fast reaction at the wellbore, low acid penetration, surface dissolution, and corrosion issues, while alternative organic acids suffer from low solubility and thermal stability problems, and chelating agents like EDTA have slow biodegradation and reduced effectiveness.
Innovation Solution
The use of glutamic acid N,N-diacetic acid (GLDA) and/or methylglycine-N,N-diacetic acid (MGDA) solutions, which are effective in forming wormholes in calcium carbonate with high solubility and stability, reducing face dissolution and fracturing risks, and can stimulate both calcite and dolomite cores without corrosive issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HCl is used for matrix acidizing in carbonate formations, then wormholes are formed to improve production, but face dissolution occurs at low injection rates consuming large volumes of acid with negligible conductivity increase
Solution Approach 1:
The patent changes the chemical parameters of the acidizing fluid by using organic acids (acetic acid, formic acid) and their blends instead of conventional HCl. This parameter change allows the acid to react with carbonate formations at lower injection rates without causing excessive face dissolution, thereby reducing acid consumption while maintaining productivity improvement through wormhole formation.
Solution Approach 2:
The patent employs composite acid formulations combining multiple organic acids (e.g., acetic acid and formic acid blends) to achieve synergistic effects. This composite approach optimizes both the dissolution rate and wormhole propagation characteristics, reducing the volume of acid needed while effectively creating conductive channels for improved production.
2Strength
If HCl is injected at low injection rates to prevent fracturing the formation rock, then corrosion and face dissolution occur, but high injection rates cause fracturing
Solution Approach 1:
The patent changes the chemical composition parameter from inorganic HCl to organic acids with different reactivity characteristics. This parameter change allows operation at intermediate injection rates that prevent formation fracturing while minimizing face dissolution and corrosion, as organic acids exhibit more controlled reaction rates with carbonate minerals compared to HCl.
Solution Approach 2:
The patent uses organic acids that are less corrosive and can be injected at rates that optimize both formation integrity and treatment effectiveness. These acids provide sufficient reaction activity for wormhole creation without the excessive corrosivity of HCl, effectively replacing a harmful substance with a milder alternative that achieves the same functional goal.
3Productivity
If EDTA is used to stimulate carbonate porous media by sequestering metal components, then dissolution occurs without requiring hydrogen ions, but solubility in HCl is low and biodegradation is slow
Solution Approach 1:
The patent replaces EDTA with organic acids (acetic acid, formic acid) that are more soluble in water and readily biodegradable. These simpler organic acid molecules provide effective carbonate dissolution through proton donation without the solubility and environmental persistence issues of EDTA, achieving stimulation effectiveness with a more environmentally friendly and operationally convenient chemical.
Solution Approach 2:
The patent changes the chemical mechanism parameter from chelation-based dissolution (EDTA) to acid-based dissolution (organic acids). This parameter change improves solubility and biodegradability while maintaining stimulation effectiveness, as organic acids provide sufficient proton donation capability for carbonate dissolution without the complications of chelating agent limitations.
4Reliability
If chelating agents like EDTA, NTA, and DTPA are used to prevent precipitation and remove scale, then iron precipitation is controlled, but animal carcinogen concerns and lower stability constants exist
Solution Approach 1:
The patent replaces complex chelating agents (EDTA, NTA, DTPA) with simpler organic acids that do not carry carcinogen risks. The organic acids provide sufficient scale prevention and iron precipitation control through their acidifying effect and complexation capability, eliminating health and safety concerns associated with conventional chelating agents while maintaining reliability.
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
GLDA and MGDA solutions efficiently create wormholes with reduced pore volumes and face dissolution, achieving higher permeability ratios and thermal stability, even at high temperatures, and are gentle on well tubulars, outperforming conventional chelating agents and acids.
Implementation Method 1
EDTA is a chelating agent that stimulates by means of sequestering the metal components of the carbonate matrix. The dissolution mechanism is different than that of HCl in that hydrogen ions are not required.
Implementation Method 2
The flow and reaction of hydrochloric acid (HCl) in carbonate porous media results in the formation of highly conductive flow channels or wormholes. Wormholes form because of the natural heterogeneity of the porous matrix and the rapid, mass transfer limited, and almost complete dissolution of the mineral in the acid.
Implementation Method 3
The acid preferentially flows to the regions of the highest permeability. These initial flow paths are enlarged by rapid dissolution of the matrix material, causing these regions to receive even more of the flow.
Data Source
AI summary
The present invention includes processes to create wormholes in carbonate reservoirs by contacting a formation with a solution comprising glutamic acid N,N-diacetic acid (GLDA) and/or a salt thereof, methylglycine-N,N-diacetic acid (MGDA) and/or a salt thereof, or a combination thereof. The present invention also includes processes to remove wellbore damage in a carbonate reservoir by contacting a damaged zone of the carbonate reservoir with a solution comprising GLDA and/or a salt thereof, methylglycine-N,N-diacetic acid (MGDA) and/or a salt thereof, or a combination thereof. The present invention further includes solutions comprising a salt and further comprising GLDA and/or a salt thereof, methylglycine-N,N-diacetic acid (MGDA) and/or a salt thereof, or a combination thereof.