| Title | DRILLING OPTIMIZATION IN HARD AND ABRASIVE GEOTHERMAL VOLCANIC ROCK USING INNOVATIVE CONICAL DIAMOND ELEMENT BIT |
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| Authors | B. Noviasta, G. Napitupulu, S. Scagliarini, M. Centeno, D. Ardianto, M.R.Y. Mardiana, A.Z. Kurnia, J.F. Bao |
| Year | 2017 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Volcanic and Pyroclastic rocks, Conical Diamond Element (CDE) Bit, ROP improvements, performance |
| Abstract | Generally, the formations found in the geothermal environment consist of volcanic and pyroclastic rocks, which are typically hard and sometimes abrasive. Roller cone tungsten carbide insert (TCI) bits are commonly thought to be the most suitable bits for volcanic rocks. Due to the nature of formation breakouts and swelling clays in the reservoir section, drilling this section as fast as possible in one bit run is necessary. However, this is not always possible since a roller cones bit’s “life” is limited by its reliability (the maximum revolutions before the bearing seal fails). The innovative conical diamond element (CDE) bit provides a solution for drilling in hard, abrasive rocks. The unique 3D geometry of the CDE in this PDC-based bit provides superior impact and wear resistance. The concentrated point-loading of the CDE enables it to fracture high-compressive-strength rock efficiently. There is no bearing seal life constraint because, being a PDC bit, the CDE bit has no moving/rotating parts. In one of the well located in West Java geothermal field, the CDE bit was used to drill two sections: 12.25-in. and 9.875-in.. The results were excellent, with both sections drilled to total depth (TD) in one run (660 and 799 m intervals, respectively). Both bits showed the capability of reaching ROP greater than 50 m/h, but the ROP had to be limited to 20 to 30 m/h due to hole cleaning concerns. Despite this controlled drilling, a 20% higher ROP compared to offset wells drilled with TCI bits had been achieved. Faster drilling and bit trip saving brought an approximate of USD 398 K drilling cost reduction. The CDE bits were pulled out of hole in very good and re-runnable conditions (0-0 and 1-1 cutter dull grade), which potentially reduced cost of procuring new drill bits in the future. |