Abstract
For improving the hole-enlarging capability, roundness and rock-breaking efficiency of the nozzle in radial jet drilling, a new structure of self-rotating nozzle was put forward. The flow structure and rock-breaking features of the self-rotating nozzle were investigated with sliding mesh model and labortary tests and also compared with the straight and the swirling integrated nozzle and multi-orifice nozzle which have been applied in radial jet drilling. The results show that the self-rotating jet is energy concentrated, has longer effective distance, better hole-enlarging capability and roundness and impacts larger circular area at the bottom of the drilling hole, compared with the other two nozzles. Forward jet flow generated from the nozzle is peak shaped, and the jet velocity attenuates slowly at the outer edge. Due to periodic rotary percussion, the pressure fluctuates periodically on rock surface, improving shear and tensile failures on the rock matrix and thereby enhancing rock-breaking efficiency. The numerical simulation results of the flow structure of the nozzle are consistent with the experiments. This study provides an innovative approach for radial jet drilling technology in the petroleum industry.
Highlights
Radial jet drilling (RJD) is a process of drilling radial horizontal holes of small diameter using high-pressure water jets (Dickinson et al 1992a, b, 1993; Landers 1998)
ICEM-CFD software was used to build the sliding mesh model, and the flow structure of the nozzle under a steady rotational state is simulated as shown in Fig. 7, in which the computational domain is separated into two sections, namely the rotator and the stator, respectively
Simulation reveals that the forward jet flow feature of the self-rotating nozzle has three peak points, among which the outer velocity attenuates slower
Summary
Radial jet drilling (RJD) is a process of drilling radial horizontal holes of small diameter using high-pressure water jets (Dickinson et al 1992a, b, 1993; Landers 1998). The milling bit makes a turn of 90 degrees to create a hole in a cased wellbore and subsequently to jet a small hole into the formation through the casing exit hole. The diameter of these radial holes is approximately 1–2 inches, and lengths. Step #1: Milling a hole in the casing with rotating drill bit (driven by downhole motor). Step #2: Blasting a lateral hole into the formation with high fluid pressure inside a nozzle head, leading to a high exit velocity jet
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