Abstract
Formation drillability is one of the most important aspects for planning and designing a new oil/gas well since the factors affecting the drilling performance have complex relationships between formation properties, drill bit design and operational parameters. In view of the high operating cost of drilling rigs, if Rate of Penetration (ROP) can be enhanced, it will reduce open-hole formation exposure time and complications associated with it, resulting in significant savings in drilling time and cost can be realized.
Normally bit engineers utilize the assumed lithology from mud logs and detailed depth-wise lithology of offset wells. The lithology can also be interpreted from conventional logging data such as Sonic, Gamma and Density. Furthermore, the rock's compressive strength is calculated using Compressional / Shear travel time (Sonic log), Bulk density (Density log) and Shale content (Gamma log).
These utilized tools to detect the lithology and rock mechanical properties have an extent of uncertainty due to effects either related to the borehole or drilling fluids that require extensive corrections. That degree of uncertainty subsequently can affect the drill bit design criteria, selection and viability of performance-enhancing features.
This present paper reveals a new practical approach as a solution to minimize uncertainty in terms of bit design and selection by utilizing wellbore imaging either LWD and/or Wireline borehole images and lithology & mineralogy from either wireline mineralogy logs "Pulsed Neutron" and/or ROQSACN instrument to precisely deliver an accurate input data to the drill bit design/selection software modules.
