Rock drilling using hot supersonic jet / Perfuração de rochas por jato supersônico quente
AUTOR(ES)
Fernando Luiz Viegas
DATA DE PUBLICAÇÃO
2004
RESUMO
This work discusses the possibility of applying the thermal spallation technique i.e., the use of hot supersonic jets for drilling and tunneling processes, on certain rocks of interest of the oil drilling industry. This technique was successfully used on granite rocks achieving high penetration rates (1 to 10 m/hr) compared to conventional techniques. An experimental unit using Oxygen - Natural Gas, was developed based on previous studies and operated under different oxidizer to fuel ratios (O/F) hitting flat granite surface samples with the objective of checking the applicability of that method for drilling this kind of rock. It was investigated the drilling performance under several oxidizer to fuel ratios and with the variation of the distance between the drilling jet unit exit plane and the rock surface. The operation of the unit indicated the importance of using a coupled refrigeration system and a displacement mechanism for drilling into the rock surface. The results showed a well defined penetration behavior with the change of the drilling distance from the rock surface (Stand-off distance), where larger hole equivalent diameters were obtained with the approach of the drilling unit to the rock surface. It was observed also that the drilling performance is not strongly influenced by reasonable oxidizer to fuel ratio changes where small jet temperature changes are imperceptible as compared to the temperature required to start the spallation process which is around 800 K. It was also observed the importance of the jet momentum in the process, which seems to be the main factor for achieving high penetration rates. Finally, the small drilling unit used in this work led to the unavoidable occurrence of scale factors due to the small amounts of energy released during the tests.
ASSUNTO(S)
propulsion combustion supersonic jet flow propulsÃo combustão fluxo de jato supersônico penetração combustÃo thermal spallation penetration combustion granite granito rochas descamação térmica rocks
