Bit Performance Evaluation in Southern Italy

The paper is aimed to compare three indexes for bit performance evaluation, cost-per-metre (CM), Specific Energy (SE) and Bit Index (BI), tested by mining data from the Formation Drillability Catalog (FDC) conceived and prepared at the Exploration & Production Division of Eni Group (Italy). At present, the most utilized methods for bit performance evaluation are mainly based on CM. This approach is a good reference system, but it is not well suited for keeping into account drilling difficulties due to formation variability, directional drilling conditions, etc. Basically, the FDC is a novel classification of drilled formations, aimed to the geomechanical characterization by means of a large number of significant drilling parameters, each one referred to single Minimum Interval (MI), a new procedure of geological and geomechanical subdivisions of the formations. Inside the FDC, five wells recently drilled in Southern Italy have been identified and tested for bit performance evaluation. Here, 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 bit performance evaluations. Results of this case study showed that cross correlations between BI and SE can help the bit selection, pointing out the best bit for each formation and for each phase. BI, in this stage of development, proved to be economic and reliable. The quality of bit performance analysis obtained with BI and SE (through the MI concept) seems also more effective than the traditional “quick look” analysis, performed on bit records, or on the pure evaluation of the CM. The objective of the research is both the analysis of a new drilling model for bit performance evaluation, the BI, and the investigation of the possibility of BI to establish sound guidelines for the development of a tool able to help during well planning, well drilling and post-well analysis.