The Louise (LSE) is one of the primary oil-producing fields in the Pertamina EP Asset V. This area has an issue with high potential of total losses in the top section [~400 m measured depth (MD)], which causes an inability to set the 13.375-in. casing at the required depth. As a result, this problematic zone must be drilled conventionally in two different sections, 17.5 in. and 12 .25 in., whilst combating losses. Pertamina EP spent up to 10 days as nonproductive time (NPT) to combat losses, resulting in high investment cost. A new innovative method was required to face this challenge with the objective of drilling deeper through the loss zone in a single run in a more effective and efficient and a safer way. Nondirectional casing drilling technology was introduced to solve this problem. The casing drilling system simultaneously drills and runs the casing through the lost circulation zone in a single run, which provides a more efficient and a safer operation. Its plastering effect helps strengthen the wellbore by smearing cuttings into the wellbore wall, sealing pores in the formation to reduce fluid loss. At the same time, it saves the rig operating days by eliminating the loss-combating days and the dedicated casing run. The key driver of this technology is the drillable alloy casing bit specially made for drilling vertical or tangential wells, which can be drilled out by any standard PDC or milled tooth after it has drilled to total depth (TD) and the casing has been cemented in place. On the pilot casing drilling project well, this system successfully drilled 351.25 m of 13.375-in. × 17.5-in. section to the casing point in a single run passing through the problematic loss zone. The 13.375-in. casing was cemented in place, and the casing bit was successfully drilled out using a conventional 12.25-in. PDC bit. Compared to the conventionally drilled offset wells, this technology enabled up to 220 m deeper 13.375-in. casing setting depth, which consequently eliminated the necessity of loss-combating activity in the 12.25-in. hole section. The implementation of the casing drilling system solved the lost circulation problem and provided an additional benefit of eliminating a dedicated casing run. The casing drilling technology helped Pertamina EP to reduce the well drilling time by up to 4.75 operating days, saved up to USD 555,913 of drilling cost, and achieved 50 m deeper well TD compared to the plan. The pre-execution engineering work was one of the key activities leading to the success.

Well X is a deepwater exploration well with the carbonates primary target. The water depth ranges from 2700 to 3400 ft and the well was drilled vertically to 14630 ft MD. The main objectives of this operation was to optimize drilling performance while maintaining safe drilling practice and minimize potential failures. One of the ways to optimize the drilling is to have an excellent bit selection to determine the best bit for the application. Traditionally, due to limitation of the data, bit records from offset wells or fields becomes the only main source to select a bit. But sometimes, the selection becomes trial and error because of the availability of the data for evaluation. A Rock Strength Analysis (RSA) software now becomes a mandatory requirement for the pre-job planning to select a bit. Using the log data from offset wells, a bit selection software based on Unconfined Compressive Strength (UCMPS) calculation was used to optimize the bits for all section of Well X. The Dynamic FEA Modeling has also been used to contrast the drilling dynamics using several bit options for each section. The analysis is capable to simulate downhole drill string behavior with detailed components model including bits, reamers, driving systems, and all of the BHA components up to the surface. It includes axial, lateral, and torsional vibrations check, and also providing safe drilling parameter roadmaps to be applied in the field. The simulation is based on the cutter-rock interaction data from lab-test and has a wide range of lithology to make the result as accurate as possible. The integration between the RSA software and the Dynamic FEA Modeling resulted the best bit and parameter roadmaps for this application. Compare to the traditional way, this integrated method can reduce the risk of having poor bit performance in the field. The recommended bit and parameter guidance for each section was then applied to drill Well X and generated satisfying ROP without any NPT related to bit performance. The bits also came out from the hole with 1-1 average dull grade due to the excellent stability of the drilling system. The hard carbonates formation target in 8.5-in and 6-in section was successfully drilled in one run to TD with low shock and vibration. Even the bits only consume 3-6% of total drilling cost, it has a huge effect to the drilling performance. Combination of RSA and Dynamic FEA Modeling in bit selection process becomes a very effective practice to prepare an exploration drilling program with limited offset well data.

In geothermal drilling application, one of the challenges faced by drilling engineers is the optimization of drilling bit which govern the key success of drilling performance. It should be aligned with recent key performance indicator such as meet the subsurface target comprehensively while optimizing the drilling cost. A typical formation in geothermal wells that consists of various types of volcanic and igneous rock should be identified carefully because the high range of hardness and abrasiveness value will respectively affect the bit. Hence, the improvement of conventional drilling bit should be carried out to enhance the drilling performance. For so many years, Tungsten Carbide Insert (TCI) bits were implemented in the geothermal drilling application because it is believed to be the most effective bit to drill hard formation. However, the TCI bits are limited by the maximum revolution the bit can achieve before the bearing seal fails. In some application, it needs 3 to 4 TCI runs to finish 9.875-in section. Some of the bits were also pulled out of the hole with undergauged condition due to formation abrasiveness. Implementing a conical diamond element (CDE) on a PDC can increase the bit durability. CDE provides significant improvement of wear and impact resistance to the bit. The point loading of this cutter is more concentrated to the formation, allows the bit to remove the rock in more efficient way. It has been discussed that the CDE bit can improve the ROP and meterage drilled, eliminating the tripping time due to bit changes as it does not have KREV limitation, and has a better trajectory control. Usually, 3-5 TCI bits were used to drilled 9.875-in section in one of geothermal well located in Hululais Field, Sumatera, with average meterage of 200 – 250 m per bit. Drilling dynamics FEA modeling was performed prior to the run of CDE bit to check the drill string vibration and provide stable drilling parameter roadmap for this bit. A CDE bit was run to drill this section and the result was excellent by drilling 600 m in a single run. The ROP was improved by around 35% compared to the maximum TCI's ROP. The bit generated less reactive torque fluctuation compared to TCI, allowed the bit to have better directional control. The CDE bit was pulled out of the hole with good dull grading (2-1-WT-A-X-I-CT-TD). By improving the ROP and eliminating the tripping time, the drilling cost can be reduced. With the downturn of oil and gas business, geothermal projects in Indonesia is raising. CDE bit is becoming a breakthrough to optimize the drilling operation in by substituting TCI runs with huge amount of potential cost savings.

Pertamina EP recently executed an exploration drilling project in Sumatera area. The objective was to evaluate the oil reserves contained in the fractured volcanic basement reservoir zone. The very hard (26,000 psi average compressive strength, with spikes of up to 50,000 psi) and abrasive nature brought drilling challenges, in particular, how to effectively and efficiently fail and fracture the rock. In a well in the previous drilling campaign, 10 runs of bit were required to complete the 294-m interval hole section containing basement formation. Various roller cone and PDC bit designs were utilized, with a resulting maximum penetration rate capability of 1.25 m/h and maximum run interval capability of 56.44 m. Another well with a basement interval of 463 m consumed 11 bit runs with maximum run drilling interval and penetration rate of 64 m and 1.56 m/h, respectively. A conical diamond element (CDE) bit was proposed to achieve more efficient drilling in the basement. The 3D geometry of the conical diamond elements, which are placed across the bit blade, provided both a superior impact and wear resistance and concentrated point loading onto the formation; these characteristics enable the bit to cause failure and fracturing of the hard-to-drill rock more efficiently. A diamond layer in the bit is twice as thick as that of a conventional PDC cutter; this enhances impact strength and improves overall bit durability. CDE bits were implemented to penetrate the basement formation in two different wells in Sumatera area. The wells were designed as directional J-type wells with maximum inclination of 70°. In the first well, eight-bladed and seven-bladed CDE bits were run with an excellent result of 131-m and 176 m of drilling interval achieved, respectively, yielding up to 211% of drilling meterage capability improvement (compared to the previous well). The rates of penetration (ROP) generated by CDE bits were also large; up to 4.17 m/h ROP was achieved (instantaneous on-bottom ROP reached up to 20 m/h), which was equivalent to 333% improvement. In the second well, the seven-bladed CDE bit generated 230 m of drilling interval with 3.27 m/h ROP, improving the offset well performance by 259% (in terms of interval) and 109% (in terms of ROP). The CDE bit significantly saved operating time and cost by improving the drilling speed and, most importantly, eliminating unnecessary trips to change the bit. The estimated potential savings from CDE bit utilization in these two wells reached more than USD 1.1 million. The drilling optimization in Sumatera yielded insights into CDE design and features appropriate for basement application, and the engineering study behind the successful execution, actual drilling operation, and run performance comparison provided information for future such operations.

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