This project drilled in Sin Phu Horm field. The main challenge in this field is the formation. The 8.5-in section is designed to drill through the hard and abrasive sandstone formation (known as Nam Phong formation) with unconfined compressive strength (UCS) between 6,000 and 24,000 psi and peak up to 55,000 psi. Multiple bit runs and heavy set of Polycrystalline Diamond Compact (PDC) bits were observed in the offset wells with slow rate of penetration (ROP) and short intervals, which resulted in a high drilling cost. In the offset runs, the average interval was observed between 200 and 300 meters and average on-bottom ROP ranged from 2 to 8 m/hr. Worn cutters were the main dull characteristic in the offset PDC bits and the bits were pulled out of hole due to slow ROP. Due to the challenging formation, the goal was to increase the interval per bit run and ROP which resulted to reduce the number of bit trips and drilling cost. Looking at the dull grading of the offset PDC bits, it was obvious that the slow ROP was caused by the cutters worn by the abrasive and hard Nam Phong formation. The fixed-cutter PDC bits were run in the offset wells and worn cutters were observed in the shoulder area. The worn portion of the cutter occurred only in the exposed side, while the portion in the cutter pocket remained intact. Utilizing the portion in the cutter pocket helps to prolong cutter life, increase the ROP, and bit life longevity. Thus, it can help to reduce undesired bit trips. Based on the worn cutter observation, the new design of the 8.5-in PDC bit equipped with innovative 360 rolling cutter (RC) bit was proposed. A comprehensive vibration simulation drilling parameters roadmap were provided to minimize shock and vibration. Two bits were run with rotary steerable BHA to drill Nam Phong formation in the field. The first bit drilled 431 meters at an average ROP of 6.8 m/hr and the second bit drilled 391 meters at an average ROP of 5.5 m/hr. Two runs using the 360 RC bits drilled 822 meters in total of 1,236 meters entire interval of Nam Phong formation, which was equivalent to 66%, achieving the operator's goal while saving 2.2 days solely from two runs of RC bit. This success increased the operator's confidence to run 360 RC bits in the subsequent wells to reduce the number of bit trips and increase the ROP. This paper will discuss the application and evolution of 360 RC bit, along with the result achieved by the bit fitted equipped with this cutter in Thailand onshore.

Mid Nam Phong Formation in Thailand’s Sinphuhorm Field consists of hard and abrasive sandstone with unconfined compressive strengths (UCS) of 12,000–24,000 psi. Polycrystalline diamond compact (PDC) drill bits used for the 8.5-in. section through this formation were providing low rates of penetration (ROPs) and showing heavy wear, with just 50–180 meterage drilled per run. Multiple bit runs were raising drilling costs. A new drill-bit design to address these challenges is presented. Rolling cutter (RC) 616—an 8.5-in. drill bit with 16 mm cutters that rotate 360°—is holding the ROP record in offset wells, delivering 3.1 m/h compared with the average 2.15 m/h, a 44% improvement. Rolling elements use the entire circumference of the cutting edge to cut the formation, enabling them to stay sharper and longer. Conical diamond elements (CDE), which provide improved impact strength and greater resistance to abrasive wear, replaced some of the conventional cutters. Based on this result and lessons learned, a new and more robust bit design was proposed featuring 19 mm rolling cutters and conical diamond elements. To combat the damaging vibration observed in offset wells, which could further reduce ROP and increase the likelihood of premature drill-bit and downhole tool failure, a special bottom hole assembly that combined a rotary steerable system and a downhole motor was deployed to reduce stick/slip. Comprehensive simulations provided a detailed road map of drilling parameters that were used to minimize shock and vibration. The new 8.5in. drill bit and BHA drilled the entire section through the Mid Nam Phong Formation in one run and at a record ROP of 4.9 m/h—58% higher than the maximum rate achieved by the RC616 bit—saving 57.8 hours. The assembly also drilled an additional 179 meterage into the Lower Nam Phong Formation, eliminating the separate bit run that had been required in offset wells. The customer saved 2.9 days or USD 130,000 in total and a new standard of drilling performance was established. The new concept of PDC bit combining 19 mm rolling cutters and conical diamond elements expands the limit of PDC bit durability drilling hard and abrasive sandstone formation. This new type of bit can efficiently drill in those challenging geological condition reducing the drilling time and cost. This paper will discuss the application and evolution of rolling cutter bits, along with the results achieved by this bit.