Delayed HF Acid Composition for Deeper Sandstone Penetration
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Solution Overview
Problem
Conventional acidizing fluids react too quickly with subterranean formations, leading to shallow penetration, formation damage, and reduced permeability due to rapid reaction with clays and silicates, especially in sandstone formations.
Innovation Solution
An aqueous delayed acid system containing an organic bifunctional compound, urea or urea derivative, organophosphonate, and optionally zirconium or boric acid compounds is used to retard the reaction of HF with the formation, enhancing wormhole creation and penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional acidizing fluids (HCl-HF) are used to stimulate sandstone formations, then the acid reacts quickly with silica and silicates to create conductive channels, but the reaction rate is too rapid causing shallow penetration and formation damage
Solution Approach 1:
The patent introduces an organophosphonate compound as an intermediary substance that forms a protective film on clay surfaces. This mediator allows the HF acid to react with silica and silicates while preventing excessive reaction with clays, thereby enabling deeper penetration without sacrificing reaction effectiveness. The organophosphonate acts as a controlled interface between the acid and formation minerals.
Solution Approach 2:
The patent modifies the chemical composition parameters of the acidizing fluid by adding organophosphonate compounds and adjusting the HF concentration. This parameter change slows the reaction rate sufficiently to allow deeper penetration while maintaining effective stimulation of the formation. The modified fluid composition enables controlled reaction kinetics.
2Productivity
If HF reacts quickly with clays and silicates, then conductive channels are formed, but precipitation of alumina and silicate complexes occurs plugging pore spaces
Solution Approach 1:
The organophosphonate compound serves as a mediator that prevents direct excessive interaction between HF and clay minerals. By forming a protective film, it eliminates the harmful precipitation reaction while preserving the beneficial conductive channel formation. This intermediary approach resolves the contradiction between productivity enhancement and harmful precipitate formation.
Solution Approach 2:
The patent converts the potentially harmful rapid reaction with clays into a beneficial controlled process. The organophosphonate modifies the reaction pathway so that clay interaction becomes controlled and productive rather than harmful and precipitate-forming. The harmful effect is transformed into a controlled, beneficial contribution to formation stimulation.
3Reliability
If HF dissolves clay in cementitious materials, then near-wellbore permeability is enhanced, but the sandstone matrix becomes unconsolidated and damaged
Solution Approach 1:
The patent applies local quality control by using organophosphonate to selectively modify the reaction at different locations. Near the wellbore, controlled clay dissolution enhances permeability, while the protective film prevents excessive dissolution that would weaken the matrix. This spatially differentiated reaction control resolves the contradiction between permeability enhancement and matrix strength preservation.
Solution Approach 2:
The organophosphonate compound acts as a protective intermediary that prevents uncontrolled clay dissolution. It allows sufficient clay removal to enhance permeability while preventing the matrix from becoming unconsolidated. The mediator ensures that the strengthening and permeability enhancement functions are both achieved without compromising formation integrity.
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 system allows deeper and more effective wormhole formation, reducing formation damage and increasing permeability, even at elevated temperatures, without the need for polymers.
Implementation Method 1
by forming a temporary protective film on clay surfaces during reaction of the HF
Implementation Method 2
The presence of the organic bifunctional group and urea or urea derivative in the fluid delays the reaction of the fluid with bentonite clay in the formation
Implementation Method 3
The acid or acid-forming material reacts with minerals in the formation and forms conductive highly branched flow channels or wormholes
Data Source
AI summary
A polymer-free fluid may be used to delay reaction of hydrofluoric acid with a subterranean formation. The fluid contains an organic compound having a bifunctional group, HF or a HF-generating compound, urea and an organophosphonate.