GLDA Chelating Fluid for Sandstone Acidizing
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Solution Overview
Problem
Current acidizing processes using HCl in sandstone formations, particularly those containing illite, lead to degradation of clay minerals, fines migration, and reduced permeability due to the swelling and mechanical dislodgement of illite particles, causing plugging and damage to the formation.
Innovation Solution
The use of a fluid containing glutamic acid N,N-diacetic acid (GLDA) or its salts, which selectively dissolves calcium carbonate while minimizing illite degradation, thereby improving permeability and reducing fines migration, is employed in the matrix acidizing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HCl is used for matrix acidizing in sandstone formations, then carbonate dissolution and permeability improvement are achieved, but illite degradation and fines migration occur causing formation damage
Solution Approach 1:
The patent changes the chemical parameters of the acidizing fluid by using GLDA (glutamic acid N,N-diacetic acid) instead of conventional HCl. This substitution fundamentally alters the chemical interaction mechanism: GLDA selectively chelates calcium from carbonate minerals through coordination chemistry, while its milder acidity preserves illite clay structure. The patent specifies using GLDA at concentrations of 5-30 wt% in aqueous solutions, maintaining pH between 2-7, which optimizes carbonate dissolution while preventing clay degradation and fines migration.
Solution Approach 2:
GLDA acts as a chelating intermediary that mediates between the acidizing process and the formation minerals. The chelating agent forms stable complexes with calcium ions released from carbonate dissolution, facilitating the acidizing reaction while the organic structure of GLDA provides a gentler chemical environment that doesn't attack illite clay minerals. This intermediary mechanism allows carbonate removal without the harmful side effects of strong mineral acids.
2Loss of substance
If HCl is used to dissolve calcium carbonate, then scale removal is effective, but illite particles swell and dislodge causing plugging
Solution Approach 1:
The patent modifies the chemical parameters by replacing strong mineral acid (HCl) with a chelating agent (GLDA) that operates through a different chemical mechanism. GLDA removes calcium carbonate through chelation rather than simple acid dissolution, which occurs at a slower, more controlled rate. This parameter change prevents the rapid pH drop and violent reaction that cause illite particle dislodgement and swelling, thereby eliminating fines migration and plugging problems.
Solution Approach 2:
The patent converts the potential harm of acidizing-induced clay damage into a benefit by using GLDA's selective chelation properties. The chelating agent's organic structure and moderate acidity transform the aggressive acid-clay interaction into a selective calcium-chelation process. This converts what would normally be a harmful side effect (clay degradation) into a controlled process that achieves scale removal while preserving formation integrity.
3Speed
If strong acid is used for stimulation, then carbonate dissolution rate increases, but formation damage and wellbore plugging increase
Solution Approach 1:
The patent changes the kinetic parameters of carbonate dissolution by using GLDA, which provides a sustained, controlled dissolution rate through chelation mechanics. Unlike HCl that causes rapid, uncontrolled dissolution, GLDA's chelating action releases calcium ions at a moderated pace through stable complex formation. This controlled kinetics maintains formation integrity by preventing rapid pressure changes and mechanical stress that would damage the formation structure.
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 GLDA-based process enhances permeability, prevents illite degradation, and reduces wellbore damage, leading to improved oil and gas production by maintaining the integrity of the formation and minimizing the formation of damaging fines.
Implementation Method 1
a fluid that contains glutamic acid N,N-diacetic acid or a salt thereof (GLDA)... GLDA acts much more selectively on the calcium carbonate in the formation and dissolves this carbonate material
Implementation Method 2
HCI affects the structure of clay minerals commonly found in sandstone... When contacted with HCI the aluminum layer of these clays is extracted, leaving an amorphous silica gel residue
Implementation Method 3
These clay minerals can swell rapidly when contacted with fluids with a different salinity, by incorporating water into their crystal structure
Implementation Method 4
Fines migration results from mechanical dislodgement caused by the drag forces exerted on the particles by gas or fluid flowing through the pores
Data Source
AI summary
The present invention relates to a process for treating an illite-containing formation, preferably a sandstone formation, comprising introducing a fluid containing glutamic acid N,N-diacetic acid or a salt thereof (GLDA) into the formation, and relates to a fluid containing GLDA, a surfactant, and a corrosion inhibitor that can be used in such a process.