Optimization of drilling design at different well depths with respect to specific energy

Drilling operations cost millions of Dollars and its success depend largely on some key parameters. Some of these parameters include wait on bit (WOB), rate of penetration (ROP), revolution per minute (RPM) and specific energy, also known as specific mechanic energy. In the design of the drilling program, keen interest must be paid to their variation, else, drilling problems which will lead to non-productive time will ensue. Therefore, this study focused on the optimization of bit design through selection of the bit with lowest specific energy possible to reduce drilling cost and improve efficiency via the consideration of critical parameters such as WOB, ROP drilling cost per foot and specific energy (Mechanical specific energy).
In this study, data were collected from 5 wells – ASSA North 004, ASSA North 005, ASSA North 006, Gbetiokun 7 and Benisede, all in Niger Delta. Specific energy was computed using mechanic energy and specific energy relations while the cost optimization was done using drilling cost relation. These data were carefully analyzed and the results of specific energy for the five wells selected wells were obtained. The values of the specific energy at desired depths were used to track the performance of drill bits at that depth. The bit used for ASSA North 005 was found to be most suitable as it maintained lowest specific energy for different depths.
The study therefore gave an insight into the importance of specific energy of the drill bit while carry out bit selection for an efficient and cost-effective drilling operation. The bit used for the drilling of ASSA North well was selected because it has the minimum specific energy.