Jakarta - Drilling is the spearhead of the upstream oil and gas and geothermal business. This activity contributed greatly to the capital expenditure (CAPEX) of PT Pertamina (Persero). RKAP-2018 shows the investment costs for drilling amounting to USD 2,085 million or 62.7% of the total upstream Pertamina ABI activities.
Based on that data, every effort to improve the efficiency and convertibility needed is the concern of the workers involved: the execution phase, the execution phase, until the drill tower is dismantled to be moved to another location. This will be realized when the high number of non-productive time (NPT) in Operation Warming can be as low as possible. For geothermal well drilling, the biggest cause of NPT is due to pinched pipe problems (jammed pipes). Among Pertamina's Upstream Subsidiary from 2015 to 2017, the pipeline of cases experienced by PT Pertamina Geothermal Energy (PGE) is 56% of the total NPT. This has resulted in an increase in drilling costs of USD 849,900 per well.
"Stagnant pipes often occur in geothermal reinforcement operations because the route often passes through the circulation loss zone so the drill cuttings (cutting) can not lifted to the surface. Accumulated cuts with large concentrations will accumulate in the drill pipe package (package off) resulting in a pipe being pinched, "said Zainuddin Salman, Senior Drilling Specialist at the Upstream Technical Center (UTC).
According to Zainuddin, these conditions can actually be overcome by doing aeration drilling (drilling using air and fluid). That is, creating under balanced conditions in the well so that cutting drilling can be lifted to the surface. However, the problem in aerated operations has so far been using conventional methods, with the design of parameters carried out by trial and error. As a result, in terms of engineering practice does not get a good design, the results are not optimal because the cutting is not fully lifted.
"Anticipating these problems we did an innovation by designing software called Pertamina Aerated Drilling Simulator (PADSim). The aim is to optimize the design of aeration drilling parameters for drilling geothermal wells. Optimization is done from the pre-drilling phase, during operation, and post-drilling or post mortem, "Zainuddin added.
Furthermore, Zainuddin explained that in the design of PADSim aerated drilling Boyun Guo method was used to evaluate geothermal well data. The PADSim software usage simulation starts with collecting the data needed as parameters in the modeling scenario. Next, input into PADSim. The simulation results obtained in the form of the following data: ECD (equivalent circulating density), ESD (equivalent static density), ECD-ESD, Ann. Dynamic P (annular dynamic pressure), Ann.Static P (annular static pressure), Dynamic-Static, Mix Density, Annular Velocity, Kinetic Energy, and Gas-Liquid Rate Window (Working Window Area).
Indicator of the success of the results of this simulation, if the conditions are under balance and the parameters used in the good working window area, then these parameters can be a reference in the operation of applying aerated drilling to geothermal wells. Determination of aeration drilling parameters with PADSim, was able to reduce NPT due to pinched pipes by 71% (110 hours) from the original total NPT of 56% (156 hours), to 17% (46 hours).
In the end, drilling cost managed to save up to 59.6% or USD 506,900 / well from USD 849,900 / well, with a total value creation of USD 4.6 million. "This PADSim has been applied to nine PGE geothermal drilling wells in Ulubelu, Hululais, Bukit Daun and Lumut Balai Fields," concluded Zainuddin.
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