The requirement of drilling in very close proximity to adjacent wells in surface hole section has been common as field become more crowded. This is true especially in offshore mature field where the last wells are drilled on a dense platform. In Santan Field, East Kalimantan, conductor pipes were driven between the existing wells since sidetrack or platform extension options were not available at the time while there are still opportunity for infill and step out wells. This situation introduces challenges on well construction in term of collision avoidance since the spacing between the wells are tight from surface point. The distance between slots is as low 1 meter from center-to-center, and 0.64 meter between wall-to-wall. Directional works was also required at shallow depth to kick of the well as per trajectory requirement. The risk of unplanned intersections with adjacent well can lead to financial loss, personnel safety as well as environmental issue. A comprehensive risk assessment were conducted during the planning phase as the safety of drilling operation has been one of the main concerns. Mitigations plan were then formulated with the objectives to manage the negative consequences to acceptable level. During the planning phase, detail anti-collision procedure was executed to evaluate the collision risk. On the field, several activities were carried out on adjacent wells prior to rig move in as mitigations measure: 1) Rig less resurvey, 2) Well integrity inspection, and 3) Well barrier placement. While drilling, following strategies were performed: 1) GWD utilization, 2) Monitoring on subject and adjacent wells, and 3) Collision-tolerant drilling bit application The all-surface hole were drilled safely without any HSE or reliability issue. No major indications of well collision were observed. However, the drilling time took bit longer than usual performance due to drilling controlled manner for anti-collision precautions. This paper explain how well collision mitigations was implemented in Santan Field, East Kalimantan, which can be a reference for further drilling as a successful case of top-hole drilling on a dense fixed platform. The method is expected to gain economic value, which is notably beneficial in mature field.

PT Pertamina Hulu Indonesia ("PHI") was founded in December 28th, 2015 as a subsidiary of PT Pertamina (Persero) ("Pertamina"). PHI was established as operation holding company to operate, manage, and conduct upstream activities in working areas, which were handed over to Pertamina by Government of Indonesia ("GoI"). The corporate objectives of PHI are to maintain production, to increase reserves, to conduct exploration activities and to assist/provide guidance in terms of HSSE policies of the working area. Recently, PHI has three subsidiaries: PT Pertamina Hulu Mahakam ("PHM"), PT Pertamina Hulu Sanga Sanga ("PHSS"), and PT Pertamina Hulu East Kalimantan ("PHKT"). Each subsidiary requires many approaches to restrain high natural declined rate related to drilling, workover, and well services activities. Consequently, Pertamina as the new Operator had to immediately conduct such activities even prior to effective date of its operatorship. Pertamina has invested in PHI through its first subsidiary since 2017 through drilling 15 wells, 12 workover, and hundred of well services activities. In addition, 7 new Plan of Development(s) ("POD"s) have been agreed for 180 new drilling jobs in 2018 onwards to support production target. Meanwhile for other subsidiaries, Pertamina immediately conducted upstream activities consist of 2 new drilling jobs, 9 workover & 70 well services for its second subsidiary, and 10 workover & 59 well services for its third subsidiary, right after the blocks were handed over. To ensure drilling and well intervention activities conducted properly, many material and services contracts must be prepared and available on time prior to program started, such as Drilling Rig Services, Drilling Fluid Services, Cementing Services, Electric Logging Services, Wellhead Services, Coiled Tubing Unit Services, et cetera. It has to be started from the beginning of and completed within the transition period. However, throughout transition period, PHI was dealing with some concerns due to many parties involved, especially regarding information restriction and confidentiality included into legal issue. In addition, PHI had also limited time and drilling personnel resources to prepare the contracts required to execute drilling and well intervention program. To encounter challenges above, the first thing to be prepared was Transfer Agreement ("TA"), and both parties (PHI and former Operator) to align rights and responsibilities of each party must sign it. PHI was succesfull in providing all required contracts for the continuation of transition and operation activities at PHI subsidiaries. Over the transition period, PHI already providing the procurement contracts directly related to drilling and well intervention activities, as follows: 158 contracts from former Operators and 60 new procurements for the new Operators. This paper will describe the successful contract strategy implementation of three subsidiaries in PHI which proven to be an efficient example of working area transition period in term of contracts.

Santan is a mature gas field in East Kalimantan, Indonesia, where infill wells are being drilled to increase production rates. A crowded offshore platform in the Santan Field increases well trajectory complexity and presents a heightened risk of wellbore collision issues. The high number of wells on this directional pad in the shallow water drilling environment results in densely populated existing conductor pipe. Thorough drilling assessments and anti-collision directional drilling mitigation practices are key to successfully executing safe and reliable drilling operations. To further mitigate the likelihood of a well control situation resulting from a collision with a neighboring conductor or casing, a 17.5 in. IADC Classification 115 Steel Tooth (ST) rolling cone bit with special heel technology was utilized in the Santan field. This is the first time this technology has been applied in Asia Pacific. The ST bit employs continuous disk shaped heel rows on all three cones rather than conventional ST chisel shaped heel row teeth which have multiple sharp cutting edges. The special disk heel rows are designed to deflect off casing in the event of a collision in order to minimize damage to conductor or casing. The use of the special disk heel technology bit has yielded positive results to date. The bits have successfully and safely drilled in a critical zone where the center-to-center distance between slots was as low as 1m. The drilling performance and well trajectory targets were achieved. Reduced drilling parameters were used as per anti-collision and lost circulation practices, however, the overall rate of penetration (ROP) and directional behavior with the special disk heel bit was similar to conventional ST bits used in offset wells without collision risks. Turn and build rates of up to 4.8°/100 ft were achieved on a bent motor bottomhole assembly, while the average distance to the plan at the end of the section was only 10.59 ft. A series of laboratory casing collision tests was conducted during the development of the special disk heel bit which demonstrated a 75-80% reduction in casing collision damage as compared to a conventional IADC 115 ST bit. Overall, this technology minimizes the detrimental effects should a collision occur, without sacrificing ROP or steerability performance. The special disk heel ST bit has proven to cause significantly less damage to casing from a collision event than any other bit type – ST, tungsten carbide insert (TCI), or PDC bits, while still providing excellent ROP and steerability in soft formation, shallow water applications. This technology allows operators to more confidently place additional wellbores in crowded offshore template environments for greater field development from a single platform.