Injection String Corrosion Solids Quantification for Injectivity Loss
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Solution Overview
Problem
Existing methods fail to quantify the solids generated by corrosive processes in injection strings, leading to unpredictable and irreversible injectivity loss and potential string degradation, especially in wells injecting desulfated seawater, due to the difficulty in measuring oxygen content and corrosion rates.
Innovation Solution
A method using the Perkins and Gonzalez modeling to adjust injectivity history and perform flow tests on rock samples, allowing direct quantification of suspended solids without measuring oxygen or corrosion rates, by comparing pL values from well history and plug tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If desulfated seawater is injected into the reservoir, then water quality for injection is improved and plugging should be prevented, but severe losses of injectivity still occur due to unquantified corrosion solids generated in the injection string
Solution Approach 1:
The patent introduces an intermediary measurement system that indirectly quantifies corrosion solids in the injection string by analyzing the relationship between injection pressure, flow rate, and reservoir response. This mediator approach allows detection of solids generation without direct measurement capability in the injection string, resolving the information loss problem while maintaining reliable injectivity monitoring
Solution Approach 2:
The patent implements a feedback mechanism where injectivity test results are continuously monitored and used to adjust injection operations. By establishing baseline injectivity values and comparing actual performance against these baselines, the system provides feedback on corrosion solids impact, enabling proactive management of injectivity loss before severe degradation occurs
2Measurement precision
If corrosion monitoring is performed in the injection string, then solids generation can be detected, but measurement complexity and cost increase due to difficulty in measuring oxygen content and corrosion rates
Solution Approach 1:
The patent extracts the measurement problem from the complex injection string environment and relocates it to surface-level analysis. By taking out the measurement function from the subsurface injection string and performing injectivity tests at the surface, the system achieves corrosion solids quantification without the complexity of in-string sensors, reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent creates a simplified copy of the injection system for measurement purposes. Instead of measuring directly in the complex injection string, the system uses injectivity test data that replicates the corrosion solids impact in a controlled surface environment, enabling accurate quantification without complex in-string measurement devices
3Reliability
If injectivity tests are performed frequently to monitor corrosion impact, then early detection of problems is improved, but production time is lost due to well shutdowns
Solution Approach 1:
The patent applies partial action by performing injectivity tests at optimized intervals rather than continuously or too frequently. By determining appropriate test frequencies based on corrosion risk assessment and previous test results, the system achieves early problem detection while minimizing well shutdown time, balancing reliability improvement with production time loss
Data Source
AI summary
The present invention addresses to a method for quantifying the loss of injectivity associated with corrosion products, comprising a methodology to estimate the suspended solids generated from the corrosion process of injection strings, aiming at allowing the identification of wells with problems, definition of strategies and damage removal, as well as acting preventively and avoiding severe losses of injectivity and string degradation, consequently avoiding production losses. The developed method can be applied to any well with available injectivity history, where tests are required on representative rock samples and under controlled conditions (known water quality) for reference and application of the experimental correlation.