Evolution of Re-Entry Well Drilling Performance to Reduce 60% Well Cost: Making the Impossible Possible Towards the Second Life of Mahakam
Authors: Haryasukma Kresna Prabu , Nurmida Arrofi , Saputra Rangga , Saptawirawan I Gede Suryana , Andhika Lutfi , Hutahaean Ray Henry Jimmy 
Published: October 2022

Abstract
Mahakam block is a concession area of oil and gas fields currently operated by Pertamina Hulu Mahakam. This block is located across the Mahakam offshore and delta in East Kalimantan. Mahakam block has been producing oil and gas since more than 40 years ago and is categorized as brownfield due to its marginal reserves. Coming from that situation, new wells are required to sustain field production. With limited available slots on existing platform, drilling thru re-entry wells is introduced. However, conventional re-entry drilling operation is still not satisfactory to meet the economical cut-off for the remaining marginal reserve.
A comprehensive re-entry well drilling strategy is continuously developed to optimize re-entry well drilling operation and significantly reduce the well cost. The strategy involves various optimizations from all drilling aspects. The first phase of re-entry well drilling evolution aims to eliminate invisible lost time from conventional re-entry drilling operation, by implementing rigless Plug and Abandonment (P&A) of parent well, eliminating BHA trips for milling casing & rathole during sidetrack preparation, and performing direct logging thru sidetrack window with wireline for reservoir data acquisition. After the first phase of re-entry well drilling evolution is established, the second phase of re-entry well drilling evolution is implemented to further reduce the well cost to meet the economic cut-off for the remaining marginal reserve, by focusing on optimization of drilling performance aspects, such as BHA optimization, fit to purpose bit selection, enhanced drilling parameter and fast connection.
The result of comprehensive optimization of re-entry well drilling operation is very promising and shows a positive impact. At the beginning of re-entry well introduced in Mahakam, the well was completed within 32.3 days of well duration for 1 section drilling interval. The implementation of optimizations was performed in stages to assess the feedback thoroughly for better results thru the first phase and second phase of re-entry well drilling evolution, resulting in gradually reduction of well duration and also the well cost. The latest implementation in Peciko field where the well can be successfully completed within 7.2 days and becoming the fastest development well drilled in Offshore Mahakam area. The well cost is also significantly reduced by up to 60% compared to the first re-entry well performed with conventional method. The most important thing, all the initiatives have been executed in a safe manner without any major operation issues and successfully unlocked remaining marginal reserve to prolong the sustainability of Mahakam.
The result of comprehensive optimization of re-entry well drilling operation significantly boosts the confidence for offshore field development, unlocking the way towards the Second Life of Mahakam. This strategy will become the new standard in drilling new development wells in Offshore Mahakam area to better adapt to the economic challenges. Furthermore, all the initiatives are also very feasible to be applied in other areas outside of Mahakam for the re-entry well campaign.