Estudo experimental da força de impacto e do coeficiente de descarga de bocais ejetores utilizados na perfuração de poços de petróleo

Abstract

The knowledge of turbulent flow pressure loss through the drill bit is fundamental for drilling optimization, since major discrepancies have been found between measured values and those predicted by models. The present paper examines the effect of the drill bit size, Reynolds number and distance between the drill bit and bottom-hole on the nozzle discharge coefficient and the jet’s impact force on wellbore, with data compared to the current models and correlations, as well as CFD simulations. An experimental study was carried out in an acrylic vertical pipe with a sudden contraction and water as the working fluid. The experiment was conducted with 3 different drill bits and 4 different distances between wellbore and bit, while acquiring data with the usage of pressure transducers. A differential pressure transducer was placed on the up and downstream regions to measure pressure drop around the bit, in addition to one placed on the bottom-hole to determine the jet’s impact force. Results show that the discharge coefficient decreases as the diameter ratio beta = D d increases, with data nearly coinciding with that of the CFD. However, none of the correlations used were successful when estimating the discharge coefficient under the experiment’s condition. The jet’s impact force on the center of the bottom-hole increased significantly with smaller nozzles.