The Sin Pu Horm Field is challenging in terms of formation and well location. Past experiences from offset wells in the field and nearby fields showed that drilling has been challenging due to several issues, including hole instability, severe lost circulation zones in shallow depths, steering difficulties, shock, vibration, bit and BHA damage caused by hard, dense, and abrasive formation in the deeper interval. The best strategy to optimize drilling performance and minimize drilling risk is to drill this interval with minimal steering requirements and move all directional requirements to the deeper interval. With this strategy, the main challenge now is to achieve the directional requirement through the hard, dense, and abrasive sandstones. The service company proposed drilling the section with a new-technology bit that utilizes conical diamond elements (CDEs) on the bit blade with a 7:8-lobe 5.0-stage motor. The objectives were completing the build section through the hard, dense, and compact sandstone and enabling smoother toolface control to complete the directional work. The rock strength of the formation ranges from 18,000 to 36,000 psi.
The PDC bit has CDEs with an ultrathick synthetic diamond layer that gives extra durability for drilling at higher ROP. The bit can withstand more weight on bit compared with conventional PDC bits of the same size, resulting in more mechanical energy to fail the formation more efficiently. The CDEs protect the PDC bit and makes it more stable, resulting in better toolface control.
The 8½-in directional section was successfully built from 10° to 49° with excellent toolface control and an average ROP of 3.5 m/h. The strategically placed CDEs on the bit blades in conjunction with conventional PDC cutters not only increased the point loading but also enabled smoother torque control, leading to smoother toolface control. None of the offset wells achieved the feet of drilling directional profile through this interval. The bit achieved the directional objectives and came out in good dull condition. By putting the directional requirement in the deeper section, the operator finished its well in 80 days, compared with an average of 100 days required by offset wells.
The operator accepted that the bits with CDEs are not only more durable but enable drilling directional profiles better than conventional PDC bits. The operator changed the drilling strategy to put all directional work in the 8½-in section. This strategy will increase drilling efficiency and lower the drilling risk of having directional work in the 12¼-in section that poses a challenge to formation stability. The next well is planned with the same bit with CDEs to minimize the number of runs.