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<p>Failure by burst is rare, and the burst failure of 140&#xa0;V ultra-high-strength special casing is even rarer, but this special grade of casing failed during the multiple pressure tests in a well. In this study, various experiments were conducted to analyze the burst 140&#xa0;V ultra-high-strength special casing. The experiments included macroscopic observation, outside diameter and wall thickness measurement, magnetic particle inspection, physical and chemical inspection, Rockwell hardness test, optical microscopy, scanning electron microscopy and internal pressure strength inspection. Furthermore, the theoretical analysis of pipe string mechanics and hydrostatic test simulating downhole working conditions was carried out. The results revealed the failure mode of the burst casing was ductile fracture. The burst failure reason of the 140&#xa0;V ultra-high-strength special casing was that the internal pressure of the pipe body exceeded its self-bearing pressure capacity. Based on the on-site pressure testing operations, further analysis and instantaneous pressure values generated by water hammer calculation were conducted on the sources of abnormal internal pressure. The results indicated that frequent and repeated pressure tests, as well as the instantaneous closure of the valve, resulted in the water hammer effect, causing the internal pressure of the casing to exceed its own compressive strength, resulting in instantaneous burst failure. The burst failure occurred 482.6&#xa0;meters below mud line which was a loose shallow section, because of the thin and relatively loose layers and poor cementing quality between 9.5 and 731.4&#xa0;m underground, as well as the highest dog leg degree from the wellhead to the cement return height section. Water hammer effect is common in many of the oil and gas wells, but a burst failure during the pressure tests is rare. To prevent such accidents from recurring, it is recommended to check and control the opening and closing speed of the water valve correctly during multiple pressure tests in the wellbore, to avoid the water hammer effect.</p>

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Burst Failure Analysis of 140 V Ultra-High-Strength Special Casing

  • 期刊论文

  • 发表日期：

    2025年6月6日

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  • Jinlan Zhao,
  • Zhaoxi Shen,
  • Tingting Qu,
  • Xiaolong Li,
  • Li Wang

摘要

Failure by burst is rare, and the burst failure of 140 V ultra-high-strength special casing is even rarer, but this special grade of casing failed during the multiple pressure tests in a well. In this study, various experiments were conducted to analyze the burst 140 V ultra-high-strength special casing. The experiments included macroscopic observation, outside diameter and wall thickness measurement, magnetic particle inspection, physical and chemical inspection, Rockwell hardness test, optical microscopy, scanning electron microscopy and internal pressure strength inspection. Furthermore, the theoretical analysis of pipe string mechanics and hydrostatic test simulating downhole working conditions was carried out. The results revealed the failure mode of the burst casing was ductile fracture. The burst failure reason of the 140 V ultra-high-strength special casing was that the internal pressure of the pipe body exceeded its self-bearing pressure capacity. Based on the on-site pressure testing operations, further analysis and instantaneous pressure values generated by water hammer calculation were conducted on the sources of abnormal internal pressure. The results indicated that frequent and repeated pressure tests, as well as the instantaneous closure of the valve, resulted in the water hammer effect, causing the internal pressure of the casing to exceed its own compressive strength, resulting in instantaneous burst failure. The burst failure occurred 482.6 meters below mud line which was a loose shallow section, because of the thin and relatively loose layers and poor cementing quality between 9.5 and 731.4 m underground, as well as the highest dog leg degree from the wellhead to the cement return height section. Water hammer effect is common in many of the oil and gas wells, but a burst failure during the pressure tests is rare. To prevent such accidents from recurring, it is recommended to check and control the opening and closing speed of the water valve correctly during multiple pressure tests in the wellbore, to avoid the water hammer effect.