Industrialization One Phase Well Perforation in Marginal Shallow Reservoir while Maintaining Proper Well Integrity Aspect: Successful Milestone in Tunu Field, Delta Mahakam, East Kalimantan.

Abstract

Delta Mahakam facing continues production decline, the marginal stake in shallow reservoir is currently considered to be produced in order to combat production decline. A break thru innovation by implementing One Phase Well (OPW) is the simplest well design in Pertamina Hulu Mahakam regards to marginal shallow reservoir stake and cost optimization. Well architecture is only consisting of cemented tubing up to surface and conductor pipe. Perforation job is considered as the most challenging ever in well design context, it can be considered as the first perforation without any surface casing existence in the well in Indonesia. The most challenging part is implementation of simple well design to be justified as dual barrier concept during completing the well which has to be mitigated by proper risk assessment. Therefore, the objective of this project is to ensure safely perforate and produce OPW wells by implementing robust and fit for purpose mitigation. The method used is by performing specific risk assessment to determine robust mitigation and thoroughly justification in order to perforate and produce OPW with respecting well integrity aspect and dual-barriers concept. Highlight mitigation such as justification conductor pipe as external envelope containment by installing annulus bleed-off line completed with pressure safety valve, ensuring good cement quality as competence barrier, detailed and robust perforation decision tree, noise log for specific well case to ensure no communication behind casing/tubing, review formation strength and shale thickness above perforation depth, initial punch reservoir zone prior fully perforated and also intensive well monitoring during initial production phase until well is considered stable. Dedicated mitigation is then socialized and discussed with operation team on site/barge to ensure proper execution. Supervisor and team
on site also performing debriefing to team to ensure step by step job operation communicated and executed as per plan. The project can be performed safely, with 35 one phase wells (OPW) have been executed, industrialized and contributed instantaneous production gain more than 60 MMscfd without jeopardizing safety and well integrity aspect. The collaboration between engineering in town and operational in site thru effective communication and socialization of mitigation based on risk assessment is one of the key of successful and safely operation. All mitigation stated in risk assessment has been implemented properly. No integrity issue observed during perforation, sand treatment and production by robust mitigations. Well integrity assurance is continuously performed and monitored which also synchronized in online well integrity monitoring system.