The self-propelled force model of a multi-orifice nozzle for radial jet drilling

• A convenient model to calculate the self-propelled force of a multi-orifice nozzle was derived and validated in this paper.
• The self-propelled factor was defined which could represent the self-propelled ability of such nozzle with the same inlet.
• Two special systems to measure the forward and backward flow ratio and the self-propelled force were designed in this paper.
• To get bigger self-propelled force, the effect of the structure parameters was analyzed in this paper.

Radial jet drilling (RJD) is an effective method for the stimulation, exploration, and development of oil and gas resources. The multi-orifice nozzle is a type of highly efficient nozzle applied in RJD. It generates the self-propelled force to pull a connected hose moving forward to form a radial hole. However, there are few studies on the self-propelled ability of the nozzle, and there is no model for the calculation of the self-propelled force. This paper developed a convenient model to calculate the self-propelled force and defined a factor to represent the self-propelled ability of the nozzle. The proposed model was validated by means of experiment and numerical simulation. To achieve a stronger self-propelled ability, we investigated the effects of the number, angle, and diameter of the orifices on its self-propelled ability. The results show that the forward orifices exert a negative effect on the self-propelled ability, whereas their angles present a positive effect. With an optimal angle, the backward orifices primarily generate the self-propelled force. Although an enlarged orifice diameter can improve the performance of the nozzle, it still has an optimal value for the limitation of flow rate and jet pressure. This study provides a reference for the design of multi-orifice nozzles and hydraulic parameters for radial jet drilling technology.