Theories and Applications of Pulsed-Jet Drilling With Mechanical Specific Energy

Summary Mechanical specific energy (MSE) is the amount of energy required to destroy a unit volume of rock. The main work of this study is to bring the hydraulic energy of a pulsed jet into an MSE model and further analyze the mechanism of improving the rate of penetration (ROP) for pulsed-jet drilling on the basis of the model. Laboratory experiments are used to obtain the relationship of bit hydraulic horsepower between pulsed jet and continuous jet, and then the MSE model of pulsed-jet drilling is established. According to the MSE theory, the major mechanisms of improving ROP in pulsed-jet drilling are changing the breaking strength of rock and improvement of downhole-cuttings-cleaning efficiency. Field tests and data presented in this study showed that this model could be used to evaluate drilling efficiency and identify abnormal conditions for pulsed-jet drilling. All tests were operated with similar parameters and on the same drilled formation. The field results illuminate that pulsed-jet drilling has higher drilling efficiency compared with conventional drilling. Moreover, the specific patterns for abnormal conditions can be detected in real time in the process of pulsed-jet drilling. This model is less ambiguous as well as robust. Therefore, it could provide theoretical support for the wide application of pulsed-jet drilling.