DOI: 10.11648/j.sd.20261404.25 ISSN: 2331-0650

Integrated Drill Bit Hydraulic Optimization and Mechanical Factor for Directional Drilling

Herianto null, Rivandi Adiguna
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The “ARD-01” well is a directional well with a final depth of 7,585 ftMD, penetrating the limestone Tuban Formation. At the 8 ½” section, a drilling issue arose in the form of a suboptimal hydraulic program due to insufficient bit power, as indicated by a BHHP/HPs ratio of 7.63%. Under these conditions, the downhole mud motor operated at 112.5 rpm with a Rate of Penetration (ROP) of 75 ft/hr, which could potentially lead to bit balling and cutting regrinding due to cuttings buildup in the borehole, thereby reducing rock fragmentation efficiency and increasing the risk of non-productive time (NPT). The hydraulic evaluation and optimization conducted in this study utilized the Bit Hydraulic Horsepower (BHHP) method, which is considered effective because it focuses on the total hydraulic energy that aids in cuttings removal. BHHP accounts for the combination of pressure and flow rate, with a target BHHP/HPs ratio of approximately 48%, since a portion of the hydraulic horsepower, around 18% is used to operate the downhole mud motor. This relationship determines the desired drilling rate, particularly in the design of the downhole mud motor, to ensure adequate rotational speed (RPM) as a mechanical factor. The results of drilling hydraulics optimization achieved by changing the actual flow rate from 450 gpm to an optimized flow rate of 530 gpm and the actual pressure from 2100 to an optimized pressure of 4200 psi using a series connected triplex pump yielded an increase in the BHHP/HPs ratio of 48.20% which meets the recommended hydraulic parameters for directional drilling with a downhole mud motor. Under these conditions, the downhole mud motor speed increased to 132 rpm, resulting in a Rate of Penetration (ROP) increase from 75 ft/hr to 90 ft/hr under average conditions and reaching 105 ft/hr under optimal conditions. These results indicate that optimizing pressure and flow rate using the BHHP method can increase the hydraulic energy available at the bit, thereby improving drilling efficiency.

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