Insights into the radial water jet drilling technology-Application in a quarry

In this context, we applied the radial water jet drilling(RJD) technology to drill five horizontal holes into a quarry wall of the Gildehaus quarry close to Bad Bntheim, Germany. For testing the state-of-the-art jetting technology, a jetting experiment was performed to investigate the influence of geological heterogeneity on the jetting performance and the hole geometry, the influence of nozzle geometry and jetting pressure on the rate of penetration, and the possibility of localising the jetting nozzle utilizing acoustic activity. It is observed that the jetted holes can intersect fractures under varying angles, and the jetted holes do not follow a straight path when jetting at ambient surface condition. Cuttings from the jetting process retrieved from the holes can be used to estimate the reservoir rock permeability. Within the quarry, we did not observe a change in the rate of penetration due to jetting pressure variations.Acoustic monitoring was partially successful in estimating the nozzle location. Although the experiments were performed at ambient surface conditions, the results can give recommendations for a downhole application in deep wells.

Effect of the structure of backward orifices on thejet performance of self-propelled nozzles

Self-propelled nozzle is a critical component of the radial jet drilling technology.Its backward orifice structure has a crucial influence on the propulsive force and the drilling performance.To improve the working performance of the nozzle,the numerical simulation model is built and verified by the experimental results of propulsive force.Then the theoretical model of the energy efficiency and energy coefficient of the nozzle is built to reveal the influence of the structural parameters on the jet performance of the nozzle.The results show that the energy efficiency and energy coefficient of the backward orifice increase first and then decrease with the angle increases.The energy coefficient of forward orifice is almost constant with the angle increases.With the increase in the number and diameter,energy efficiency and energy coefficient of the forward orifice gradually decrease,but the backward orifice energy coefficient first increases and then decreases.Finally,it is obtained that the nozzle has better jet performance when the angle of backward orifice is 30°,the number of backward orifice is 6,and the value range of diameter is 2-2.2 mm.This study provides a reference for the design of efficiently self-propelled nozzle for radial jet drilling technology.

Theoretical calculation of high-pressure CO_(2)jet in cases of composite rock-breaking based on span-wagner equation of state

Although several theoretical calculation methods for high-pressure jet are available,there is currently no theoretical model for the high-pressure CO_(2)jet based on the high-precision equation of state(EOS).To investigate the flow field of the high-pressure CO_(2)jet in cases of the composite rock-breaking under the high-pressure CO_(2)Jet and PDC cutter,a semi-analytical approach of the high-pressure CO_(2)jet is developed based on the Span-Wagner EOS and CO_(2)jet theory.The semi-analytical calculations and the physical property calculations under the action of the high-pressure CO_(2)jet are conducted with consideration of the jet pressure,the jet distance,the nozzle diameter and the jet angle.The results indicate that the distribution of the physical properties calculated by the semi-analytical approaches is similar to that obtained by experimental monitoring and numerical simulation,which indicates that the calculation method of the high-pressure CO_(2)jet presented in this paper is effective and reliable.The properties of the CO_(2)jet obtained by the theoretical calculation see a significant difference between the initial region and the jet impact region.At the temperature of 300 K,the increase of the initial pressure can effectively increase the impact force and the cooling ability of the jet.The proportion of the jet core lengths in the jet on the axis increases with the increase of the ratio of the nozzle diameter to the jet length,accompanied with the increase of the impact force of the jet.The increase of the jet angle can effectively increase the impacting force of the jet,but hampers the fluid diffusion.The study combines the theoretical calculation of the jet with the calculation of the physical properties of the high-pressure CO_(2),for comprehensively understanding the CO_(2)jet field in the composite rock-breaking under the action of the high-pressure CO_(2)jet and PDC cutter.This theoretical calculation of the CO_(2)jet based on the high-precision EOS provides an option for the convenient calculation of the CO_(2)drilling in practical engineering.

Flow field simulation of supercritical carbon dioxide jet: Comparison and sensitivity analysis

As a new jet technology developed in recent years, the supercritical carbon dioxide（SC-CO2） jet technology enjoys many advantages when applied in oil and gas explorations. In order to study the properties and parametric influences of the SC-CO2 jet, the flow fields of the SC-CO2 jet are simulated using the computational fluid dynamics method. The flow field of the SC-CO2 is compared with that of the water jet. The influences of several parameters on the flow field of the SC-CO2 jet are studied. It is indicated that like the water jet, the velocity and the pressure of the SC-CO2 jet could be converted to each other, and the SC-CO2 jet can generate a significant impact pressure on the wall, the SC-CO2 jet has a stronger impact pressure and a higher velocity than those of the water jet under the same conditions, the maximum velocity and the impact pressure of the SC-CO2 jet increase with the increase of the nozzle pressure drop, under the stimulation condition of this study, the influence of the SC-CO2 temperature on the impact pressure can be neglected in engineering applications, while the maximum velocity of the SC-CO2 jet increases with the increase of the fluid temperature. This paper theoretically explores the properties of the SC-CO2 jet flow field, and the results might provide a theoretical basis for the application of the SC-CO2 jet in oil and gas well drillings and fracturing stimulations.