Monobore Expandable Liner Extension Saves Well With Problematic Drilling Programme from Abandonment

Abstract

Abstract To circumvent or minimize non-productive time (NPT) in wells where drilling programs with problematic drilling sections would be expected, the Monobore Expandable Liner Extension System (MELES) was developed. A recent exploration project in Egypt predicted costly and time consuming drilling hazards in their well programme and planned the MELES as a contingency system should these situations be realized. While drilling the 12.25-in. hole section below the 13-3/8-in. casing, situations with caving, sloughing, and swelling shale sections, combined with lost returns were encountered. Before the 12.25-in. hole section was completed, shales packed off the drillstring and part of the bottomhole assembly (BHA) was left in the hole. The MELES was no longer a contingency, but would now be required in the casing design to reach the target evaluation depth with a sufficient hole size of 6.0-in. Casing (9-5/8-in.) was run as deep as hole conditions allowed, with a recess shoe to enable the monobore expandable liner extension below. Following drillout of the recess shoe, open hole conditions presented the same challenges previously experienced. The 8-in.outside diameter (OD) liner extension system was run, but well conditions prevented getting the expandable liner to depth and it was pulled out of the hole. Conditioning trips with increased mud weight up to 12.3 pounds per gallon (ppg), reaming and backreaming, along with an open hole cementing effort, were performed for stabilization. A second attempt was made to run in the hole. The hanger located in the recess shoe profile of the 9-5/8-in. casing and the system was expanded to the same inside diameter as the casing above. The expanded liner's shoe was now located just above the previously left BHA, but the trouble zone sections were isolated with no reduction in hole size from the previous casing. The expanded liner was pressure tested to 1,000 psi before cementing. Recess shoe ports were enabled and initial circulation established, and the wellbore did indeed pack off and build pressure, preventing full annular cement. Pressure inside the casing was applied and 15 barrels (bbl) of cement were squeezed into the hole. A casing exit was milled in the expanded monobore liner to enable bypassing the BHA that was left in the hole from previous drilling operations. The case history explored in this paper highlights overcoming substantial issues using expandable drilling liner technology via a monobore liner extension that resulted in successful installation and circulation. The preplanning, installation considerations, expansion process, lessons learned and post-deployment results will be discussed.