In recent years, most producing wells in China have entered their mid-to-late production stages, with increasing occurrences of casing damage and wellbore collapse, leading to higher difficulty and costs in oil recovery. Meanwhile, the demands for detection accuracy, instrument performance, and environmental adaptability in geophysical logging continue to rise. Consequently, improving the signal-to-noise ratio of transient electromagnetic late-time signals and enhancing detection accuracy remain key challenges in transient electromagnetic casing damage detection.
Development Train of Thought The methodology involves first correcting signals acquired under instrument eccentricity conditions, establishing a combined eccentric transient electromagnetic (TEM) casing damage detection system. It effectively differentiates layer-specific information in multi-tubing strings, enabling precise casing quality assessment and rapid interpretation for both conventional and complex well conditions-thereby improving repair success rates and expanding the technology's applicability.Subsequently, leveraging eddy current diffusion characteristics, the design employs varied-sized probes to create an auxiliary-channel-based TEM downhole detection system. This advancement achieves high-accuracy multi-string evaluation, further enhancing detection precision in layered tubing environments.
Electromagnetic Casing Flaw Detection Technology for Oil-Water Wells
It is the magnetic logging series in engineering testing, It is deployed via a test winch. Multiple magnetic probes acquire casing-related data, which is transmitted to surface processing equipment through a single-core armored cable and displayed in real time as dynamic imaging. Post-testing, dedicated interpretation software analyzes the data to generate a casing integrity distribution report.
It consists of a combined eccentric probe assembly and modular components for signal generation and data acquisition. The probes (A, B, C, D) are arranged vertically, with interposed circuits for power, signal transmission, and reception. Upper and lower centralizers ensure the tool remains centered in the casing during operation.
The four probes divide the casing circumference into four equal detection zones. They are spaced longitudinally and require depth correction of their received signals to align data onto the same plane, forming a "virtual circular array." This array positions the four probes at 0°, 90°, 180°, and -90°. The probes use an integrated design with inner transmission coils and outer reception coils, shortening the tool's length and enhancing signal sensitivity and strength. This structure offers higher resolution for distinguishing multi-layer tubing information, enabling precise and rapid assessment of casing quality in complex well conditions, including high-inclination and multi-layer wells.
By applying different phase shifts to the received signals of the array probes for weighting, the phase scanning in the phased array radar is simulated, and the applied phase shifts are optimized according to the criterion of maximum signal-to-noise ratio (SNR). Different optimization weights are applied to different frequencies to obtain the optimal performance of transient electromagnetic signals at each frequency point.
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