Casing Conductor Installation with Auger Drilling to Secure Uncompacted Surface Formation

Abstract

There are two main hazards in surface hole section in Mutiara and Pamaguan fields, loss circulation and shallow gas. Blowout incident due to both hazards occurred in Pamaguan in 2012. While influx was moving, the conductor shoe was unable to withstand the differential pressure and cracked due to influx coming up through weak area around conductor shoe (broaching). Hence conductor must be set deeper to make sure the shoe is strong enough to withstand the pressure in case any occurrence of unscheduled events. Independent Well Integrity Assessment Team (IWIAT) recommends minimum conductor depth is 250 ft. In Mutiara and Pamaguan Fields, conductor piling limited to 250 blow/ft can reach an average depth of 50 ft below ground level. It is either additional surface casing must be run or new method must be used. One of the methods that might potentially be used is auger drilling which has been used in construction industry to install conductor as a base foundation until 450 ft depth with max 59″ diameter. To implement this in field with loss circulation and shallow gas hazard (later known as dual hazards), modification of procedure is needed by adding sequences before auger drilling. Pilot slim hole drilling complete with diverter, kill mud and LCM were prepared to mitigate these dual hazards prior to enlarge the hole with auger. Auger drilling with above mitigation is well proven and thus most reliable method to reach minimum 250 ft in depth. It is the safest method since pilot slim hole is drilled using mini diverter prior to enlarge hole with auger. Auger drilling method also eliminates surface loss circulation during rig operation in shallow and uncompacted formation, casing collapse due to driven to refusal in order to reach required depth, and other subsequent well NPT that might happen in surface section. Using auger drilling to install conductor can eliminate the needs to drill additional surface section and set additional surface casing by rig to strengthen the conductor section. Saving 1 section means 3 days faster on drilling operation which means cost reduction, eliminate operational risk in surface section, and opportunity to reach deeper TD. With this saving days, one additional well can be delivered in one-year operation in Mutiara and Pamaguan Field.