Sandstone Acid Treatment Composition for Injectivity
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Solution Overview
Problem
Traditional acid treatments for sandstone formations often fail to maintain reservoir integrity and result in the formation of precipitated products, leading to rapid decline in injectivity due to the use of hydrofluoric acid, which causes formation damage and skin effects near the wellbore.
Innovation Solution
A method involving a well treatment composition comprising an aqueous solution of an ammonium salt, a non-hydrofluoric inorganic acid, and an organic acid, along with a pre-flush and post-flush fluid, is introduced to treat sandstone formations, which includes a pre-flushing step, a flushing step, and a soaking step to maintain the well treatment composition's interaction with the sandstone formation, thereby removing formation damage and enhancing injectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hydrofluoric acid is used in acid treatment, then penetration into porous rock is improved, but reservoir integrity deteriorates and precipitated products form
Solution Approach 1:
The patent changes the chemical parameters of the acid treatment by using a combination of organic acid (formic acid) and inorganic acid (hydrochloric acid) instead of hydrofluoric acid. This parameter change maintains the acid's ability to penetrate and dissolve formation damage while eliminating the harmful precipitation effects that compromise reservoir integrity.
Solution Approach 2:
The patent introduces ammonium salts as intermediary substances that mediate between the acid and the formation. The ammonium salts prevent the direct formation of harmful precipitates by interfering with the chemical reactions that would otherwise occur between the acid and formation minerals, thus protecting reservoir integrity while allowing acid treatment to proceed.
2Productivity
If hydrofluoric acid is used in acid treatment, then formation damage removal is improved, but skin effects near wellbore increase
Solution Approach 1:
The patent converts the potentially harmful effect of acid treatment into a beneficial outcome by using an acid system that dissolves formation damage without creating skin effects. The organic acid component provides effective damage removal while the absence of hydrofluoric acid prevents the formation of precipitated skin near the wellbore.
Solution Approach 2:
The patent changes the chemical composition parameters from hydrofluoric acid-based to a combination of organic and inorganic acids with ammonium salts. This parameter change maintains the effectiveness of formation damage removal while eliminating the generation of skin effects, thus improving productivity without the harmful side effects.
3Productivity
If traditional acid treatment is used, then injectivity improvement is achieved, but treatment complexity increases due to flowback stage requirement
Solution Approach 1:
The patent extracts and eliminates the flowback stage from the traditional acid treatment process. By using an acid system that does not require flowback to prevent precipitate formation, the treatment process is simplified while maintaining injectivity improvement benefits.
Solution Approach 2:
The patent segments the treatment into simpler components: pre-flush pill, well treatment composition, and post-flush fluid, eliminating the need for the complex flowback stage. This segmentation reduces treatment complexity while achieving the desired injectivity improvement through the specialized composition of each segment.
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 method effectively removes formation damage, maintains reservoir integrity, and increases well injectivity by dissolving calcium carbonate and clays, reducing clay disturbance and precipitated products, and eliminates the need for a flowback stage, resulting in improved long-term injectivity and reduced treatment complexity.
Implementation Method 1
The composition may consist essentially of an aqueous solution of an ammonium salt, an inorganic acid, and an organic acid... effectively removes formation damage, maintains reservoir integrity, and increases well injectivity by dissolving calcium carbonate and clays
Implementation Method 2
introducing a pre-flush pill comprising an aqueous solution of a first brine, a first ammonium salt, and a first mutual solvent... introducing a post-flush fluid comprising an aqueous solution of a second brine, a second ammonium salt, and a second mutual solvent
Implementation Method 3
reducing clay disturbance and precipitated products
Data Source
AI summary
Provided is a method for treating a sandstone formation with a well treatment composition. The method may include introducing a pre-flush pill, introducing the well treatment composition, introducing a post-flush fluid, and maintaining the wellbore such that the well treatment composition interacts with the sandstone formation. Further provided is a method that may introduce the well treatment composition as two pills, such as an organic acid pill and an inorganic acid pill. The well treatment composition may include an aqueous solution of an ammonium salt, an inorganic acid, an organic acid, and optionally one or more of a pH adjuster, a mutual solvent, a surfactant, and a corrosion inhibitor.