Biodegradable Acid Solution for Calcium Filter Cake Removal
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Solution Overview
Problem
Current methods for removing calcium-containing water-based filter cake from wellbores are inefficient and often require multi-step processes, leading to incomplete removal and potential damage to geological formations, with existing solutions not meeting industry standards for low steel corrosion rates and biodegradability.
Innovation Solution
A biodegradable acid solution comprising 69.5 to 93.375 wt % water, 5 to 20 wt % hydrochloric acid, 0.75 to 7.5 wt % formic acid, 0.75 to 7.5 wt % citric acid, and 0.0075 to 0.75 wt % surfactant is used to contact the filter cake at specific pressures and temperatures, achieving high removal efficiency in a single step while minimizing steel corrosion and ensuring geological formation integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional multi-step methods are used to remove calcium-containing filter cake, then removal process can be performed, but removal efficiency is incomplete and process complexity increases
Solution Approach 1:
The patent combines multiple removal mechanisms into a single acid solution formulation. The solution integrates calcium dissolution (via hydrochloric acid), organic polymer degradation (via formic and citric acids), and surfactant action into one unified treatment fluid, eliminating the need for sequential multi-step processes while achieving complete filter cake removal.
Solution Approach 2:
The invention uses a composite acid solution containing multiple active ingredients (hydrochloric acid, formic acid, citric acid, and surfactants) working synergistically. Each component targets different aspects of filter cake composition (calcium carbonate, organic polymers, and emulsified materials), and their combined effect achieves superior removal efficiency compared to single-agent treatments.
2Productivity
If strong acids are used to remove filter cake, then removal efficiency improves, but steel corrosion rate increases
Solution Approach 1:
The patent modifies the chemical parameters of the acid solution by using a combination of weaker organic acids (formic and citric) alongside hydrochloric acid, and by controlling the concentration and pH of the solution. This parameter optimization maintains effective calcium dissolution and organic polymer degradation while reducing the corrosiveness to steel equipment compared to using concentrated strong acids alone.
Solution Approach 2:
The organic acids (formic and citric) and surfactants act as intermediaries that facilitate filter cake removal through alternative mechanisms (organic polymer degradation and emulsification) that do not rely solely on strong acid corrosion. This reduces the dependence on high concentrations of hydrochloric acid, thereby reducing steel corrosion while maintaining removal efficiency.
3Productivity
If non-biodegradable chemicals are used for filter cake removal, then removal effectiveness improves, but environmental damage increases
Solution Approach 1:
The patent selects biodegradable chemical components (formic acid, citric acid, and specific surfactants) that naturally decompose in the environment. These substances maintain effective filter cake removal capabilities while undergoing biological degradation, thus eliminating persistent environmental contamination associated with non-biodegradable chemicals.
Solution Approach 2:
The invention employs biodegradable chemicals that serve their removal function and then naturally break down, analogous to using disposable rather than permanent materials. The organic acids and surfactants perform their cleaning function and then decompose through biological processes, preventing long-term environmental accumulation and damage.
4Loss of time
If single-step removal method is used, then time efficiency improves, but removal completeness deteriorates
Solution Approach 1:
The patent uses a composite acid solution containing multiple active ingredients that target different components of the filter cake simultaneously. The hydrochloric acid dissolves calcium carbonate, formic and citric acids degrade organic polymers, and surfactants emulsify remaining materials, achieving complete removal in a single application without requiring sequential treatment steps.
Solution Approach 2:
The acid solution formulation is designed to perform multiple removal functions simultaneously: calcium dissolution, organic polymer degradation, and emulsified material removal. This multi-functional approach enables complete filter cake removal through a single treatment process, eliminating the need for multiple sequential steps while maintaining removal completeness.
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 greater than 92.5% of the calcium-containing filter cake, increasing wellbore permeability by 90 to 100% and meeting OECD 301B biodegradability requirements, with a steel corrosion rate of less than 0.049 lb/ft2 per day, thus surpassing industry standards.
Implementation Method 1
contacting the calcium-containing filter cake with a biodegradable acid solution comprising 69.5 to 93.375 wt % water, 5 to 20 wt % hydrochloric acid, 0.75 to 7.5 wt % formic acid, 0.75 to 7.5 wt % citric acid
Implementation Method 2
0.0075 to 0.75 wt % of a surfactant, each based on a total weight of the biodegradable acid solution
Data Source
AI summary
A method of removing calcium-containing water-based filter cake from a wellbore involving contacting the calcium-containing filter cake with a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, and a surfactant. The method is performed at a pressure of 200 to 400 psi and a temperature of 50 to 125° C. The method removes calcium-containing filter cake made of water, calcium carbonate, a polymer or starch and a clay. The method meets industry standard steel corrosion rates of less than 0.049 lb/ft2 per day. Also disclosed is a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, and a surfactant that meets OECD 301B thresholds for ready biodegradability.