Directional drilling the 12-in. curve section in the deep gas fields in Saudi Arabia is very challenging because of the hard formations and harsh drilling conditions. The section consists primarily of hard limestone and dolomites interbedded with anhydrite. The main challenges of drilling this section include multiple bit trips and reduced rates of penetration (ROP).

To overcome these challenges, the operator, directional drilling service company, and drill bit company in collaboration developed an optimization process to create and evolve a polycrystalline diamond compact (PDC) bit design to be used on powered rotary steerable systems (PRSS).

The objective of the optimization process was to increase the ROP and the durability of existing PDC bits to eventually lead to drilling longer intervals by minimizing the number of bit trips while drilling with PRSS. The challenge required the development of a new PDC technology in conjunction with optimized drilling practices and a reliable drive system.

The challenges were overcome by implementing the specific bit design algorithms incorporated with new cutter technology, and using drilling simulation software to optimize the bit cutting structure design in directional drilling environment. Significant improvements in bit design were achieved after closing the model/measure/optimize loop. Through field testing, drilling parameter evaluation, and drilling simulation, a new 12-in. PDC bit was designed that established benchmark performances in the deep gas operations in the Ghawar field.

The successful development of the PDC bit in conjunction with the PRSS system led to record runs in the 12-in. build section. Casing-to-casing sections were drilled with an improved ROP of approximately 125%, compared to that of a conventional motor. This paper reviews the bit design and optimization process to develop the fit-for-purpose PDC bit that helped to improve the drilling performance, significantly reduce rig days, and enable early delivery of the wells in challenging deep gas drilling in Saudi Arabia.

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