Role of Geology Operation Facing the Subsurface Uncertainties, in Mitigation, While Drilling and Logging in The Mahakam Delta

Abstract

Operation in mature fields as Mahakam Delta becoming more complex and challenging. It’s due to reservoir connectivity & pressure uncertainty where some reservoirs already depleted while others might still be virgin or high pressure condition, and both condition could be drilled in same drilling phase. It will create risk of drilling kick, drilling BHA (bottom hole assemble) or wireline tool string stuck during drilling and logging, and tight drilling window. This complexity also caused by the distance between reservoir target and platform is too far that make well become highly deviated. Continuous improvement has been done by Pertamina Hulu Mahakam (PHM) including for pore pressure and geomechanic model. Since 2013 dedicated in house pore pressure and geomechanic team has been built to support drilling preparation and operation. Some study has been performed to minimize the uncertainty, such as combination of anamorphous of stress and Eaton calculation to create more accurate shale pressure prediction, methodology to calculate effect of depletion to fracture pressure in reservoirs, digitalization model for quick pressure evaluation and calculation pump stroke vs connection gas peak to estimate more accurately source of ballooning during drilling operation. With dedicated integrated geoscience team, the result of prediction is become more accurate due to knowledge and integration between all entities could be optimized to create the pore pressure and fracture gradient (PPFG) prediction. It has been proven where drilling problem due to pressure has been reduced and optimization for well design also could be implemented. Many efforts have also been conducted in data acquisition aspects. For wireline logging operation, improvement for probe type, displacement unit, high tension cable, advance fluid analysis sensor, modification of bottom tool wireline string to allow the tool run smoothly in high deviated well, and also cable creep for probe positioning has been implement in Mahakam operation. For mudlogging, some techniques are improving and optimizing such as constant volume degasser is mandatory for gas out to have accurate gas reading, gas while drilling (GWD) analysis to support fluid interpretation. All the efforts and continuation for improvement are really needed to keep the well can be delivered safely, efficient and economic.

AAPG Datapages/Search and Discovery Article #90354 © 2019 AAPG Asia Pacific Technical Symposium, The Art of Hydrocarbon Prediction: Managing Uncertainties, Bogor, (Greater Jakarta), Indonesia, August 7-8, 2019