Thin reservoirs of a few feet in thickness present challenges to well placement. The challenges generally involve remaining within the reservoir boundaries and undergoing as few exits as possible. Geosteering is typically used to optimize wellbore placement in the productive reservoir to maximize hydrocarbon production. The challenge posed by the subject reservoir in this study was a combination of the thinness of the reservoir and the highly resistive environments of the boundary, including formation heterogeneity and low porosity anhydrite formations.

Steering in this challenging environment using a rotary steerable system (RSS) resulted in premature cutting structure damage of the polycrystalline diamond compact (PDC) bits. This damage led to a significant increase in nonproductive time (NPT) resulting from tripping out of the hole for bit changes. A customized PDC bit design was necessary for the drilling operation to address the dull conditions, maintain a competitive rate of penetration (ROP), provide smooth borehole quality, and maintain low vibration levels. A new PDC bit was designed using patented multilevel force balancing technology: a new theory of PDC cutter layout in force-balanced groups. By carefully selecting the order of cutter layout groups, an even distribution of the cutting structure forces was obtained, thus reducing the imbalance forces induced as the bit entered transit lithologies.

This PDC bit design and the implementation of the integrated engineering software used to analyze offset well data, drilling parameters, bit walk tendency, and rock mechanics significantly affected the horizontal section drilling performance. A single new bit design was used to drill three laterals from shoe to total depth (TD) while achieving a new field ROP record. The bit was pulled out of hole (POOH) twice in green dull condition. The successful implementation of the multilevel force-balancing technology improved overall bit stability, reduced vibration levels, and increased the horizontal section drilling efficiency.

This paper demonstrates the successful implementation of an innovative PDC cutting structure layout using computer-aided design (CAD) and computer-aided manufacturing (CAM) software for bit design and optimization. The PDC bit design software incorporates a steering mechanism, bit/formation interaction model, and advanced rock mechanics modeling software to help predict bottomhole drilling mechanics, thus helping to create an optimized engineering solution for enhanced drilling efficiency.

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