Successful Deployment of Large Diameter Hybrid Drill Bit with Optimized Drilling Parameters Leads to Breakthrough in Days Saved

Abstract

Abstract The 22 in. vertical section in south-west Kuwait has traditionally been drilled with tungsten carbide insert (TCI) drill bits on rotary assemblies through limestones, dolomites and anhydrites, and commonly suffer severe or total losses before kickoff point (KOP) is reached. The losses and relatively slow rate of penetration (ROP) that is achieved with TCI drill bits results in high drilling fluid costs and extended periods spent waiting for water in order to build more mud. The need to reduce flow rates to lower effective circulating density (ECD) renders drilling with a polycrystalline diamond compact (PDC) bit on a positive displacement motor (PDM) unrealistic as a method of achieving a higher ROP, and so a Hybrid Drill Bit solution on a rotary assembly was viewed as a means of reducing drilling time through enhanced ROP. A 22 in. Hybrid Drill Bit was selected to drill the vertical section to KOP on a rotary assembly. The Hybrid Drill Bit drills much faster than a TCI bit but does not generate the high reactive torque levels of a PDC bit, and so can be run without a motor where flow rates are necessarily lower than ideal due to ECD considerations. In the vertical rotary section of four wells, the Hybrid Drill Bit had an average ROP 300% higher than the average ROP of TCI bits in the field, and the benchmark Hybrid Drill Bit drilled 229% faster than the field TCI benchmark bit, with flow rates reduced as low as 500 gallons per minute with total losses. These 22 in. bit runs represent the first time Hybrid Bits of this size have been run in west Kuwait and is a novel approach to the drilling challenges in these permeable formations and have delivered substantial savings in section cost.