Numerical research on rock breaking by abrasive water jet-pick under confining pressure

The efficient development of deep oil and gas reservoirs with abundant resources is conducive to meet the growing energy demand. However, it is very difficult to drill in the deep reservoirs such as tight sand gas and shale gas because of their high strength, low porosity, and low permeability. In this study, it is pointed out that developing high-efficiency drilling methods based on new combined water jets is a good approach to promote the rate of penetration (ROP) in such tight deep reservoirs. A pulsed abrasive water jet drilling tool is designed, and its dynamic work principle is analyzed. The hydraulic structure is optimized; meanwhile, the rock-breaking experiments of this structure are carried out. The results show that the rock-breaking performance of the pulsed water jet is much better than that of the continuous water jet. It is also found that the rock-breaking performance of the pulsed abrasive water jet is much better than that of the premixed abrasive water jet. In addition, the best rock-breaking standoff distance, abrasive concentration, and particle size are detected.

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Failure Mechanism and Effect of Nozzle Parameters on Abrasive Water Jet Rock Breaking

Shock and Vibration ◽

10.1155/2021/6621255 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Jialiang Liu ◽

Yujie Zhu ◽

Shujian Du

Keyword(s):

Failure Mechanism ◽

Optimal Parameter ◽

Ct Scanning ◽

Rock Breaking ◽

Water Jet ◽

Rock Fragmentation ◽

Abrasive Water Jet ◽

Parameter Mismatch ◽

Technical Parameters ◽

Particle Hydrodynamics

Abrasive Water Jet (AWJ) technology has vast application prospects in the assisted drill-blasting of tunnel excavation, with the advantages of fast-breaking speed, low tool wear, less dust, and good mobility. Nevertheless, AWJ technology has some limitations and shortcomings, such as the small effective fracturing range and parameter mismatch, which influence the fracturing effect of AWJ. To solve the abovementioned issues, it is necessary to study the failure mechanism of rock impacted by AWJ and nozzle parameter effects on rock fragmentation. Based on the coupling algorithm of Smooth Particle Hydrodynamics and Finite Element Method (SPH-FEM), in this research, the numerical model of AWJ impacting rock was established, and the result was verified with Computed Tomography (CT) scanning after the AWJ impacting rock experiment and image processing technology. Through the analysis of the stress characteristics of typical particles in the rock model at different stages and positions, the formation and expansion mechanisms of the crater and the cracks were revealed. Additionally, in this research, the comprehensive damage factor of rock (X) representing the fragmentation degree was defined. By comparatively analyzing X-values with certain technical parameters of AWJ, the importance ranking of the nozzle parameters, the effect of each nozzle parameter on the rock fragmentation, and the optimal parameter combination were also investigated.

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