Complex Well Intervention Activities to Restore the Integrity of Single Barrier High Risk Gas Well

Abstract

Abstract This paper will present one of the challenging deep gas well integrity restoration within Petroleum Development of Oman (PDO). The well showed indications of parted 4 ½" tubing post frac operations. The failure resulted in compromising the well integrity and pressure communication was found on the Annulus behind the tubing (Annulus A). Moreover, access to the bottom part of the well was lost due to tubing miss alignment which made the intervention more complicated. Downhole information were gathered using Lead Impression Block (LIB) and special Camera Runs. After Concept Design Selection utilizing engineering simulation software, an external casing patch (ECP) was found the best fit to restore the integrity of the 4 ½" cemented tubing. A specific design of the external patch including connections qualification and material selection was prepared based on gas production envelop. Unit selection was done based on intervention simulations to select a fit per purpose unit, increase the chance of success and optimize unit technical cost (UTC) The integrity of the wells is assured by PDO barrier policy which dictate 2 barriers at all times of the well cycle life for any flow path from the reservoir. Risk assessment to identify the integrity code of the well resulted in a code 9 (out of 10) classification which means that the well needed to be restored or abandoned as soon as possible. Radial Cutting Tool (RCT) was used to cut the upper part which was fished out with 2 fishing assembles. Moreover, access to the wellbore was essential to isolate the reservoir. It was successfully gained by running a 4 ½" Overshot. The isolation plugs were run via slick line at different stages of the intervention for well control reasons To verify the casing patch installation, a customized load design calculations for current reservoir conditions were performed. The integrity of the well was successfully restored and the well was put back to production after running the ECP. The ECP design was done for the first time within similar scope of work which unlocked potential for future opportunities. As well, the intervention was done for the first time using light workover unit which minimized the cost impact. Unique integrity repair plan with integrated risk assessment for high risk well interventions was done successfully to restore integrity of single barrier gas well. The idea of selecting a light workover unit underwent a thorough risk assessment and detailed engineering design to prove the concept.