| Popis: |
On 20Apr05, while bringing Mad Dog Slot W1 back on production after a brief shut-in, pressure developed on the A annulus and persisted despite repeated bleeds. Diagnostic pressure tests and logs eliminated a number of possible sources of the annulus pressure, eventually leading to the conclusion that the 9-7/8 in. production tieback had been breached. Further investigative logs led to the observation of ovalization of the production tubing. This study summarizes the efforts of the team assigned to investigate the causes of the production tubing and casing deformation. The outcome of the analysis suggests a subtle failure mode, ultimately related to attempts at annular pressure build-up mitigation. The subtlety emphasizes the importance of (a) design considerations in uncemented annuli opposite salt, (b) the importance of creating a complete cement sheath and (c) the inherent difficulties in converting an appraisal well into a producing well. The study concludes with a brief review of the changes implemented in the replacement well intended to eliminate a repeat of the identified failure mechanism(s). |
