Abstract

In Egypt's Western Desert, the Alam El-Buieb formation (AEB) and the Safa reservoirs have remained a challenge to drill because of their high compressive strengths and abrasive sandstone/siltstone formations. In the AEB and Safa formations, vertical sections are drilled regularly using several 8½-in roller-cone tungsten carbide insert (TCI) bits. To improve section performance and reduce overall cost per foot ($/ft), impregnated bits run on turbines and high speed motors were initially used. While these types of bottom hole assemblies (BHA) had advantages, they also came with disadvantages: The high- running costs and greater lost-in-hole (LIH) costs associated with these assemblies was a concern for most operators. Additionally, some rigs lacked the power to run them. These conditions motivated operators and bit suppliers to find alternative assemblies that can successfully drill challenging sections while reducing the $/ft by increasing the ROP and the footage each bit drills.

Recent advancements in polycrystalline diamond compact (PDC) bit design have made this possible. By altering PDC-bit profile, shape, cone angles, back rake angles, cutters and conducting test runs while being guided by finite element analysis (FEA) based modeling system and CFD modeling, design teams have produced PDC bits that are best suited for the targeted application (formation and rotary BHA). In conclusion, the newly designed PDC bits have shown a significant increase in ROP and footage compared to TCI and impregnated bits. The result is a significant reduction in drilling costs running PDC on rotary assemblies.

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