Research on structure design and flow field characteristics of the novel jet bit for radial horizontal drilling

The use of radial jet drilling (RJD) to exploit unconventional natural gas is an attractive study area. A self‐propelled bit enormously affects the drilling efficiency. Herein, for a straight‐swirling mixed jet (SSMJ) bit, the internal and external velocity fields were analyzed using a simulation to reveal a jet mixed mechanism. The rock‐breaking characteristics of different bit structures were investigated using laboratory experiments. A straight jet and a swirling jet were independent flowing through the impeller and were gradually mixed together in the mixing chamber inside the bit. The jets' boundary gradually dissipated along the radial direction, and the swirling jet distribution along the circumferential direction tended to be uniform. The velocity vector gradually decreased from the center to the periphery, and the energies were slowly concentrated due to the cluster‐narrowing by the conical wall until the velocity at the nozzle outlet reached its peak. Different flow fields were modulated by changing the bit structures. The diameters ratio greatly affected the distribution proportion of straight and swirling; the length‐diameter ratio primarily affected the contribution of the swirling jet to its center, and the width‐diameter ratio chiefly affected the initial formation velocity of the swirling jet, which all directly affected the depth variation along the radial and diameter of a borehole. The hole depth and diameter, erosion volume, and bottom flatness were combined to evaluate the rock‐breaking performance. The bit with a diameters ratio of 0.67, a length‐radius ratio of 0.57, and the width‐radius ratio of 0.13 had the best erosion effect. The simulation and experimental results achieved good mutual verifications. Overall, this study can guide research on the SSMJ rock‐breaking mechanism and bit design for RJD.

Section: Structure and Methodsmentioning

confidence: 99%

Section: Ssmj Bit Structure and Parametersmentioning

confidence: 99%

Internal flow field and rock‐breaking characteristics of a straight‐swirling mixed jet and its influential factors in radial jet drilling

Peng

Wei

et al. 2022

“…9 Over the past few years, some researches and field applications (eg, the self-propulsion force of the hydraulic jet bit, the radial horizontal extension limit, the borehole trajectory measurement, the rock breaking capacity of the jet bit, the calculation of hydraulic parameters) have been conducted. [10][11][12][13] Obviously, the prediction of the fracture initiation in radial lateral boreholes should be studied in depth to more effectively control the variability of fractures.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis on fracture initiation from radial micro‐hole in anisotropy formation

Zhang

Zheng

et al. 2021

“…The force generated by the jet nozzle to pull the high‐pressure hose moving forward, breaking the rock, and forming multiple lateral micro‐holes to enhance the production is called the self‐propelled force 20 . The structural parameters of a multi‐orifice nozzle play an important role in controlling the self‐propelled force, rock breaking force, jet pressure, and maximum drillable length 21‐24 . The forward orifice mainly completes the rock breaking relying on high‐pressure jetting, while the backward orifice with the function of assisting the reaming and stabilizing the jet nozzle has the function of expanding the radial hole by generating the self‐propelled force.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the factors affecting the self‐propelled force in a multi‐orifice nozzle using a novel simulation method

Zhang

2020

A multi‐orifice nozzle is the primary actuator of radial jet drilling for the stimulation of unconventional and low‐permeability reservoirs. This research developed a 3D flow field simulation model to investigate the self‐propelled force of a multi‐orifice nozzle based on ANSYS‐CFX. To evaluate the self‐propelled ability of the nozzle, investigation was performed on the effects of the angle, number, the diameter of the forward and backward orifices of the multi‐orifice nozzle, and the diameter of the micro‐hole in the radial well on its self‐propelled ability by sensitivity analysis. The results revealed that the self‐propelled force slightly increased with the angle of forward orifice increasing, and decreased with the angle of backward orifice increasing; and that the self‐propelled force had a tendency to decrease significantly with the number of forward orifices increasing, and increased slightly with the number of backward orifices increasing. The self‐propelled forces for different combinations of forward and backward orifices were obtained by the simulation method, which agreed well with those obtained by the calculation method, with an average accuracy of 95.82%. It was observed that the self‐propelled force increased substantially as the value of K (d2/d1) increased, but tended to slow down when the flow rate was within a certain range. Besides, with the increase in the diameter of the micro‐hole, the self‐propelled force reduced, and increased substantially as the inlet flow rate increased, but tended to slow down as the inlet flow rate further increased. Thus, to ensure the self‐propelled ability of the jet nozzle, a set of optimal structural parameters can be used to generate the target self‐propelled ability. The research improves the working performance of multi‐orifice nozzles and provides theoretical guidance for hydraulic radial jet drilling process.