Nitrate Treatment for Subterranean Wellbore Injectivity
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Solution Overview
Problem
Water injectivity decline due to formation damage in subterranean wells, leading to reduced reservoir pressure and oil recovery efficiency, often requiring costly continuous stimulation or halting operations.
Innovation Solution
A nitrate treatment method utilizing nitrate-reducing bacteria to convert nitrate anions into nitrogen gas, improving reservoir pressure and permeability, while controlling sulfate-reducing bacteria-induced corrosion, using compositions with varying nitrate concentrations and optionally adding specific bacteria or inhibitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If water is injected into the reservoir to maintain pressure and improve oil recovery, then reservoir pressure and oil recovery are improved, but formation damage occurs due to incompatibility between reservoir fluids and injected water, reducing well injectivity
Solution Approach 1:
The patent applies nitrate treatment to convert harmful sulfate-reducing bacteria into beneficial nitrate-reducing bacteria. The nitrate anions are reduced by bacteria to nitrogen gas, which improves well injectivity and reduces formation damage. This transforms the harmful effect of bacterial corrosion into a beneficial microbial treatment that restores injectivity.
Solution Approach 2:
The patent changes the chemical composition parameters of the injected fluid by adding nitrate anions at specific concentrations (first composition with higher concentration, second composition with 20-70% of the first, third composition with 20-70% of the second). This parameter change enables the nitrate reduction process to occur, improving injectivity while maintaining oil recovery.
2Reliability
If nitrate treatment is applied to improve well injectivity, then water injectivity is enhanced and corrosion is reduced, but additional treatment compositions and bacterial cultures must be injected into the wellbore
Solution Approach 1:
The patent segments the nitrate treatment into multiple compositions with different nitrate concentrations. The first composition has a higher nitrate concentration, while the second and third compositions have progressively lower concentrations (20-70% of the previous). This segmentation allows for controlled nitrate delivery and reduces the complexity of managing a single high-concentration treatment.
Solution Approach 2:
The patent utilizes naturally present bacteria in the subterranean wellbore to perform the nitrate reduction process. Instead of requiring external addition of nitrate-reducing bacteria, the treatment leverages the existing microbial population, simplifying the treatment process while maintaining effectiveness.
3Productivity
If multiple nitrate compositions are injected at different concentrations, then nitrate reduction is optimized and injectivity is improved, but the treatment process becomes more complex with multiple injection stages
Solution Approach 1:
The patent implements a dynamic injection strategy where nitrate compositions are injected at varying concentrations rather than a single fixed concentration. The second composition contains 20-70% of the nitrate concentration of the first, and the third composition contains 20-70% of the second. This dynamic approach optimizes nitrate reduction while managing injection complexity through systematic concentration reduction.
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
Enhances water injectivity by up to 15% and reduces sulfide production, providing a cost-effective, environmentally friendly, and reversible solution applicable at high temperatures, maintaining well injectivity and reducing corrosion.
Implementation Method 1
The nitrate treatment method may include nitrate reduction to nitrogen gas by nitrate utilizing bacteria (NUB) or nitrate reducing bacteria (NRB)
Implementation Method 2
In the methods of enhancing water injectivity into a subterranean wellbore, the nitrate anions are reduced by bacteria present in the subterranean wellbore
Data Source
AI summary
Methods of enhancing water injectivity into a subterranean wellbore may include injecting a first composition comprising nitrate anions having a nitrate concentration into a target zone of the subterranean wellbore; injecting a second composition comprising nitrate anions into the target zone of the subterranean wellbore, where the second composition has a nitrate concentration of from about 20% to about 70% the nitrate concentration of the first composition; optionally injecting a third composition comprising nitrate anions into the target zone of the subterranean wellbore, where the third composition has a nitrate concentration of from about 20% to about 70% the nitrate concentration of the second composition; and injecting water, where the water injection pressure is reduced by about 5% to 25% compared to the water injection pressure in an untreated subterranean wellbore, where the nitrate anions are reduced by bacteria present in the subterranean wellbore.