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This paper discusses the drilling operations performed on the first 3 drilling wells of the Sapi Re-Activated Development Drilling Wells with PT Hulu Kalimantan Timur. The project aims to have additional gas production from the Sapi Field which needs to be put back on production after the gas production has been inactive since the closing of the Sapi production facilities at the end of 2018. Sapi Field has been developed since the POD (Plan of Development) was approved in 2000. There were 21 development wells in total (7 wells were the re-drill wells) drilled through 14 platform slots during the development period from 2000 onwards. This re-activation drilling campaign had been planned for the 2023 Drilling Budget realization. However, the PHKT management decided to accelerate the program of drilling 7 new wells since the requirement of gas consumption in East Kalimantan must be urgently fulfilled. However, the drilling team decided to convert 3 (three) of the 7 new wells to re-drill wells so that the overall Sapi drilling campaign could be executed earlier, around the end of 2021, by optimizing the utilization of available slots at the Sapi Platform. The 1st well of the Sapi Drilling Campaign was completed safely in 30 days. The well was a re-drill that was sidetracked thru the 9-5/8” casing of a mother well that was plugged & abandoned previously. The well was completed with a cost of around 25% below budget. It was discovered that net sand was 40% higher than the prognosis with the following events encountered during drilling the well: rig stability; SIMOP operation for demolition work through an offset platform; social problems resulting from villagers' intervention; penetration of long hard sand intervals; lower FIT value than expected; and well control event to circulate high gas influence while drilling the 6-1/8” section. Lost circulation problem was potentially expected to be a drilling hazard at several depleted zones, and kick problems were also potentially to be encountered through high-pressure zones at depths deeper than 12,000 ft VD. Therefore it is a great opportunity to discuss in this paper, particularly the lessons learned through the drilling operation of these 3 (three) re-drill wells. All matters concerning the execution of drilling operations on the first, second, and third re-drills had been thoroughly evaluated. All similar potential drawbacks could be anticipated and avoided for better performance improvement. Therefore, the drilling performance of the next 4 new wells can be improved considerably. The drilling cost of the last re-drill well, Sapi-5RD2, was indicated to have significant improvement over the first well. The Drilling Division of PT PERTAMINA Hulu Kalimantan Timur had spent only around 66 % of the approved AFE budget to complete the well. Detailed operational drawbacks and evaluation processes to result from significant drilling performance improvement from one well to the other consecutive wells are discussed in detail.