Ester-Based Acidization Fluid for High-Temperature Filter Cake Removal
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Solution Overview
Problem
Current acidization methods for removing filter cakes in wells are inefficient due to rapid acid consumption and corrosion issues, especially at high temperatures, leading to localized acid release and incomplete filter cake removal.
Innovation Solution
An aqueous solution comprising esters of hydroxy acids or glycerol is introduced into the well, which undergoes slow hydrolysis at high temperatures, releasing acid capable of consuming filter cakes without premature exhaustion, using esters like lactate and tripropionin that maintain effectiveness over a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If strong mineral acids such as hydrochloric acid are directly injected into the well, then filter cake removal capability is improved, but acid consumption rate increases rapidly and corrosion damage to well structure occurs
Solution Approach 1:
The patent applies preliminary action by using drilling fluids containing acid-neutralizing materials (such as calcium carbonate, magnesium oxide, or aluminum hydroxide) during the drilling stage to pre-form a protective layer on the wellbore and formation surfaces. This preliminary protective layer is established before acidization treatment, allowing subsequent acid injection to target filter cake removal more effectively without rapid neutralization and loss of acid to the wellbore structure.
Solution Approach 2:
The patent introduces an intermediary substance approach by using soluble salts (such as calcium chloride, sodium chloride, or potassium chloride) as carriers in the acidization fluid. These salts serve as intermediaries that facilitate acid delivery to the filter cake while their solution properties help control acid distribution and reduce premature neutralization reactions with the wellbore structure.
2Productivity
If strong mineral acids are directly injected into the well, then filter cake removal capability is improved, but corrosion damage to metal parts of well structure occurs
Solution Approach 1:
The patent applies preliminary action by using drilling fluids containing acid-neutralizing materials (such as calcium carbonate, magnesium oxide, or aluminum hydroxide) during the drilling stage to pre-form a protective layer on the wellbore and formation surfaces. This preliminary protective layer is established before acidization treatment, allowing subsequent acid injection to target filter cake removal more effectively without rapid neutralization and loss of acid to the wellbore structure.
Solution Approach 2:
The patent introduces an intermediary substance approach by using soluble salts (such as calcium chloride, sodium chloride, or potassium chloride) as carriers in the acidization fluid. These salts serve as intermediaries that facilitate acid delivery to the filter cake while their solution properties help control acid distribution and reduce premature neutralization reactions with the wellbore structure.
3Productivity
If acid is injected to remove filter cake, then filter cake removal is achieved, but acid is exhausted before reaching desired treatment region
Solution Approach 1:
The patent applies preliminary action by using drilling fluids containing acid-neutralizing materials (such as calcium carbonate, magnesium oxide, or aluminum hydroxide) during the drilling stage to pre-form a protective layer on the wellbore and formation surfaces. This preliminary protective layer is established before acidization treatment, allowing subsequent acid injection to target filter cake removal more effectively without rapid neutralization and loss of acid to the wellbore structure.
Solution Approach 2:
The patent introduces an intermediary substance approach by using soluble salts (such as calcium chloride, sodium chloride, or potassium chloride) as carriers in the acidization fluid. These salts serve as intermediaries that facilitate acid delivery to the filter cake while their solution properties help control acid distribution and reduce premature neutralization reactions with the wellbore structure.
4Stress or pressure
If high pump pressures are used to inject fluid past filter cake, then injection capability is improved, but sweep efficiency of oil decreases
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and rheological properties of the injection fluid. The acidization fluid contains soluble salts and organic acids with controlled pH and viscosity parameters that allow the fluid to penetrate the filter cake at lower pressures while maintaining effective acid delivery. This parameter optimization enables balanced injection pressure and sweep efficiency.
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 slow release of acid allows for thorough distribution and consumption of filter cakes, ensuring effective removal and preventing premature acid loss, even at elevated temperatures, thereby enhancing well productivity.
Implementation Method 1
The ester undergoes hydrolysis to break the emulsion and release the acid
Data Source
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AI summary
Improved acidization methods and compositions are provided wherein the compositions comprise an aqueous solution comprising one or more esters or polyesters of hydroxy acid or of glycerol. The solution may be placed in a well where the esters or polyesters undergo hydrolysis. The hydrolysis of the esters or polyesters occurs at a slower reaction rate than that of several other known acidization esters, such as diethyleneglycol diformate, at temperatures higher than 600C or even higher than 1000C. Thus, the acidization solution may be distributed substantially throughout a region in a well where acidization is required before hydrolysis is completed, despite being exposed to relatively high temperatures. The hydrolysis may result in the slow release of an acid that is capable of consuming all or most of an undesirable substance in the well, e.g., a filter cake.