Prediction of Drillability of Sedimentary Rocks

Fundamental considerations like drillability and tool wear may be pondered for the development of deep well drilling for oil and gas, and tunneling projects. Careful considerations of key parameters may enhance the advance rate, operational costs, activity completion timeline and inventory control for spares. NTNU/SINTEF developed drilling rate index (DRI), bit wear index (BWI) and cutter life index (CLI) to quantify drilling and TBM related parameters. Until now, most of the research work has been carried out to develop models in order to recognize the effects of rock properties on drillability. However, very little if no studies have been conducted on the prediction of bit wear using BWI. This work deals with the effects of different geo-mechanical parameters of rocks on the drillability and the bit wear. The work shows that both drillability and bit wear are affected by the physical and strength parameters of rocks. Moreover, various statistical models (with R-2 >= 0.83) have been developed through simple linear regression analysis (SLRA) and multiple linear regression analysis (MLRA) for the prediction of NTNU/SINTEF indices (DRI and BWI).