Search for a command to run...
Abstract In gas storage, well integrity is a critical aspect to ensure safe conditions for storing gas and maintaining the continuity of gas supply. In northeast China, wells are commonly drilled and completed to store gas during summer and produce it for energy consumption during winter. Gas storage wells are typically drilled with production casing, intermediate casing, and surface casing sections, each cemented up to the surface and completed with tubing and pack-off of the production casing for gas injection and later production. High sustained pressure in annuli A, B, and C is a common problem during gas injection, with the worst-case scenario being gas leaks at the surface, where gas bubbles and high levels over the Lower Explosive Limit (LEL) are detected, limiting the volume of injected gas. Operators conducted various pressure tests to diagnose potential weak points and suspected multiple leaks within the complex well structure, but no leak points were identified. There was insufficient pressure build-up analysis to estimate the size of the leaks in annuli A, B and C. The extremely cold environment during winter posed additional safety concerns for logging operations, complicating data acquisition for diagnosing the well problems. Furthermore, there was tight time limitation for logging operations before gas production was scheduled to begin. To overcome these obstacles, a comprehensive methodology was proposed, including noise logging with water injections to stimulate the leaks, despite limitations due to water source availability and cost constraints. Ultimately, a thorough 8-day diagnosis program was executed with full cooperation and support from operator. The program involved both continuous and stationary modes of array noise detection tool logging in static and dynamic conditions, as well as continuous digital gauge surface pressure measurements. The integration of noise spectrum and temperature analysis indicated suspicious leak points at various depths within the tubing. Further investigation using beamforming analysis on array acoustic waveforms successfully pinpointed all the leaks located at the tubing collars and rate estimation at leak points utilizing phase flow rate estimation algorithm. The phase flow rate estimation algorithm provided estimated leak rate, enabling assessment of the severity and impact of each leak which were crucial for developing targeted and effective remediation planning. The success case study underscores the importance of reliable logging diagnosis in maintaining well integrity and ensuring the safe operation of gas storage facilities. By leveraging advanced diagnostic tools and adopting a multi-faceted approach, operators can effectively manage well integrity issues, mitigate risks, and enhance safety and efficiency of gas storage operations. Ensuring continuity of gas supply for winter energy consumption is crucial, and this case study demonstrates how a well-coordinated diagnostic and remediation strategy can achieve those goals.