Marlin Failure Analysis and Redesign; Part 1, Description of Failure

Abstract

Abstract The Marlin Field is located in the Gulf of Mexico, Viosca Knoll Blocks 871/915, and was originally intended to be produced from a TLP via five dry tree penetrations. First production from the A-2 well began in November, 1999. Shortly thereafter a minor, but persistent tubing leak occurred. Between November 7 and November 20, Well A-2 was alternately flowing and shut-in, depending on shakedown of the surface equipment and availability of the pipeline. On November 20, the casing pressure jumped to shut-in tubing pressure, signifying a major tubing failure. This first of three related papers describes the actions of an incident investigation team formed to evaluate the failure of Well A-2. Possible failure modes investigated by the team include: Helical buckling of the production tubing, with or without the combined loss of a tubing centralizer; Crushing of the tubing by ratcheting displacement from a failed centralizer; Lateral deflection of the subsea wellhead; Collapse of the production (and/or intermediate) casing onto the tubing due to one or a combination of: Hydrate formation outside the intermediate casing due to gas migration from a shallow hydrocarbon zone, with subsequent dissolution during initial production; Non-uniform loading of the production casing due to the geometry of the sub-mudline pack-off tubing hanger; Leak of the production casing connection; Annular fluid expansion; Formation of a heat pipe in the production tubing by production casing / riser annulus; Casing wear on the intermediate casing; Excessive initial pressure resulting from setting the casing hanger seal assembly in the subsea wellhead; Inadequate performance of the tubing or casing, either due to an incorrectly run or inadequately manufactured joint. The current installment will, by deduction from both analysis and the physical evidence, narrow the field of candidate failure modes to a small subset. The application of these results and analytical techniques as incorporated into the re-design of the subsequent completions is to be addressed in the second paper of the series1. The final paper describes the implementation of the redesign as an insulated tubing completion2.