Unlock Very Shallow Reservoir in Safe Manner by Ensure Well Integrity Status: Success Story Pilot Well at Tunu

This is the authors' abstract. We don't add key points for this paper.

Tunu is giant mature gas and condensate producer. As a part of achieving the national production target, stakes in the Tunu Very Shallow layer which were not previously booked as a reserve, will become a zone of interest for production. The definition of very shallow development itself is a reservoir with target depth limited above 500 mSS (300 - 499 mSS). General risks in very shallow reservoir such as; excessive sustained casing pressure due to cement channeling from reservoir target to surface, crossflow from reservoir target to shallowest open reservoir, uncontrolled hydrocarbon release due to fracture formation and sustained casing pressure in outermost annulus of adjacent wells. By acknowledging the risk and challenge, risk assessment should be developed by engineering review and specific mitigation should be implemented to ensure good well integrity can be achieved prior perforation, during perforation, after perforation & sand control means installation and during production. The engineering review includes validating well barrier, ensure pressure from reservoir is not exceed shallowest perforation fracture pressure, minimum requirement of 50 meters accumulative shale layer thickness, good annulus cement quality, and running noise log if found anomaly annulus pressure for this trial campaign. Noise log shall be performed post perforation if observed leak rate more than 15 scfm. Additionally, specific mitigation involves installation of bleed of line on outermost annulus, utilization of multi-purpose barge and well testing barge ready to mobilize in case emergency, perform punch perforation prior main perforation to observed reservoir pressure, daily well monitoring post perforation until consider stable, and PSHH flowline to be set below the fracture pressure at the shallowest perforation depth. Prior re-classification stakes as reserve and in industrialization development at Tunu, trial campaign are performed by determining wells candidate to comply with milestone of trial campaign. Implementation of engineering review and specific mitigation measures in a pilot well with satisfactory result and unlocked estimate stakes about 0.12 Bcf. The successful of pilot well, the engineering review and the implementation of specific mitigation strategies set a strong foundation for considering the very shallow reservoir as a development target and industrialized. This determination can be solidified by evaluating the results from multiple trial campaigns to give solid safe conclusion in producing very shallow reservoir with robust and comprehensive data.