Bit performance evaluation by means of bit index and formation drillability catalogue

The paper illustrates an innovative numerical index for bit performance evaluation called Bit Index (BI), applied on a new type of well database known as Formation Drillability Catalogue (FDC). A dedicated research programme (jointly developed by Eni E&P and the University of Bologna) studied the above BI by deploying drilling data (bit records, master log, wireline log, etc.) together with a calculation of dull bit evaluation. This index is implemented with data collected inside the FDC, a novel classification of Italian formations aimed to the geotechnical and geomechanical characterization of the formations, through the new concept of Minimum Interval (MI). FDC was conceived and prepared at Eni E&P Div., and contains a large number of significant drilling parameters. Five wells have been identified inside the FDC and tested for bit performance evaluation. The values of BI have been calculated for each bit run, and have been compared with its Cost per Metre (CM). The case study analyzed bits of the same type, diameter and run in the same formation. Preliminary results showed that the BI methodology implemented on MI’s classification of the FDC improved consistently the bit performance evaluation, and helped to identify the best performer bits. Moreover, FDC turned out to be functional to BI, since it discloses and organizes formation details that are not easily detectable or usable from bit records or master logs, allowing for targeted evaluations. At this stage of development, the BI methodology proved to be economic and reliable