This paper presents a case history of a systematic approach to extending the typical open-hole section length seen in ExxonMobil Exploration & Production Malaysia Inc (EMEPMI) wells offshore the east coast of Peninsular Malaysia. Incremental improvements in shallower wells have allowed acceleration of the learning curve for use in the deeper, more complex wells. This approach was successfully completed at the Larut Platform with project wells breaking Malaysian records for open-hole section lengths and total measured depth, while minimizing the casing strings required and overall well cost.
With prior drilling experience limited to relatively shallow wells of about 4000 meters (m) measured depth (MD), there was a concern that Malay Basin formations would not support open-hole sections with lengths greater than 2200m. To meet this challenge, successive Larut wells were planned with incremental increases in open-hole section length of up to 200m. Drilling parameters were monitored and documented in these wells to calibrate predicted torque and drag values for future extended reach wells in the development program.
Drilling the first well in Larut Field resulted in little non-productive time associated with open-hole length or other related problems. As the open-hole section was systematically lengthened in subsequent wells, clean up time associated with circulation and back reaming operations at connections was optimized to compensate for the increased hole section length. Drilling data from the early wells provided credible friction factors which when used to model torque and drag in future extended reach wells did not predict any significant increase in risk for extending the open-hole sections.
The documented data in the early step-out wells allowed the team to refine and execute best practices in hole cleaning and operational practices to suit even longer hole section drilling. The Larut program successfully pushed the envelope and produced two Malaysian record breaking wells with total depths (TD) greater than 5900m initially and then 6300m, both with a horizontal displacement (HD) to true vertical depth (TVD) ratio of 2.5. The project savings associated with pushing the envelope exceeds $4,000k USD to date.