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.

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