The Application of Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) in the Study of Drilling Bit Nozzles

Abstract

ABSTRACT Two non-destructive optical methods - Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV), as innovative methods in drilling process efficiency studies, were applied in velocity measurements of jets coming out of drilling bit nozzles. Scientific papers and textbooks published on the subject contain results of the velocity distribution below a nozzle based on single-point measurements. This involved the use of Pitot tubes and Hot-wire anemometers, while LDV has only recently been introduced in jet bit studies. Hydraulic parameters regularly monitored and calculated in drilling activities are jet velocity, hydraulic horsepower and impact force. Existing methods provide these parameters to be calculated only at the nozzle outlet. At the same time the area of important jet action, lying at the bottom of the hole and in between, is not adequately investigated. Recently developed PIV enables velocity measurements to be carried out simultaneously over the entire profile of the flow. PIV permits great range of velocities to be measured with high accuracy in various media, experimental setups and types of the flow. In this paper a preliminary study of high jet velocities coming out from nozzles having circular, square, rectangular and elliptical openings is discussed. Testing facilities and results obtained both with PIV and LDV are presented. Three-dimensional nozzles tested may have their application in drilling bit design, especially in PDC bits. Moreover, employed techniques allow effective evaluation of nozzles, better understanding of the high velocity jet behaviour and may significantly contribute to the optimization of drilling hydraulics. In addition, possible other applications of PIV and LDV in domain of petroleum engineering are discussed.