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 A is a geothermal well in K field, located in the Jambi area of Sumatera. The pilot hole of the 17.5-in section was drilled to total depth (TD). However, a 13.375-in casing running difficulty was experienced afterwards. A dedicated cleanout bottomhole assembly (BHA) was run, but this became stuck. The decision was taken to plug the pilot hole with a cement plug and to perform an openhole sidetrack. The difficulty in running the 13.375-in casing is caused by collapsing formation from the borehole wall. The commonly run casing/liner tieback system has no rotational capability when an obstruction is encountered while running the casing. The 13.375-in × 17.5-in nondirectional casing drilling technology was proposed as the solution. The main component of this technology is the drillable alloy casing bit, which drills on standard casing that is rotated at the surface. The casing bit is equipped with PDC cutters and nozzles with the same function as those in a conventional PDC bit. The casing can be fully rotated while applying weight to cut through the obstruction. The casing drilling system successfully set the 13.375-in casing to 849.72-m measured depth (MD), 314 m deeper than the initial point of the casing running obstruction. The drilling/reaming capability of the casing bit helped in cutting all the formation filling the predrilled hole. The cementing process was executed well, with good integrity to the surface, shown not only by a surface return during the cement top job but also by a good cement bond log (CBL) result. This eliminated the requirement of having a casing/liner tieback system, which saved operating time and cost. The ability to set the casing deeper enabled sealing off the total loss zone. Consequently, the 12.25-in section drilling could be executed without penetrating the problematic zone, which improved drilling efficiency.
Casing while drilling Level 2 was introduced to mitigate problems in the surface section of Mutiara and Pamaguan Field in East Kalimantan. These two fields have historical shallow gas and loss circulation hazards in surface section. Following a blowout incident in Pamaguan in 2012, new policy was introduced for drilling the surface section in Mutiara and Pamaguan. A pilot hole must be drilled, and additional surface casing shall be set. Although considered safe, longer drilling days and vulnerability to repeated loss circulation made this method inefficient. A new approach to mitigate the problem was proposed by introducing casing while drilling Level 2 in 2020 drilling campaign. Many papers already discussed about the effectiveness of casing while drilling to mitigate loss circulation. However, a limited number of papers discuss casing while drilling to mitigate shallow gas. Costeno et al, 2012, discussed the use of casing while drilling to mitigate shallow gas. However, the risk of shallow gas was low and there was no shallow gas record during the execution. This paper specifically discusses about utilizing casing while drilling (CWD) technology to mitigate not only loss circulation, but also shallow gas risks during surface hole interval. Both hazards occurred in several wells during job execution and CWD with its plastering effect has managed to drill troublesome surface hole safely, thus making it the better alternative to achieve efficient drilling in comparison with the previously used pilot hole method.
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