Abstract
Major operator is drilling in an exploratory field, located in East Jordan, targeting sandstone reservoir approximately 2,600 m below the surface. Historically, the operator drilled these underbalanced wells with conventional roller-cone and polycrystalline diamond compact (PDC) bits. The drilling project included a 26-in. hole through a tough and highly interbedded formation of mudstone, sandstone and siltstone down to depth of 1,350 m. Inconsistent drilling performance of PDC bits resulted in short run intervals with poor dull conditions. The roller-cone bits also inconsistently drilled the entire interval, achieving slow penetration rates with short runs.
horough in-depth engineering analysis of all available data including rock strength, bit dull, bottomhole assembly, drilling parameters and downhole vibrations, identified the possible root causes for this poor performance and led to a new 26-in. hybrid bit design to overcome the drilling challenges and improve the overall drilling efficiency.
The 26-in. hybrid bit technology with combined elements of PDC bits and tungsten carbide inserts (TCI) was deployed. This combination overcame the drilling challenges in this application and achieved all the operator objectives by drilling the entire 26-in. hole in one run, replacing three bits used to drill the same interval in the offset well, saving five rig days over the planned AFE drilling days.
This paper provides a detailed description of the operational challenges in this application. It then introduces the concept of the new hybrid bit design and provides recommendations based on the performance achieved. After a description of the implementation and operation execution of drilling 26-in. hole in this challenging application, the paper concludes with a discussion of the benefits and value added to the operator by the deployment of this new design approach, highlighting the reduction in number of trips for bit changes.
