Rock breaking mechanism of electrode bit in heterogeneous granite formation and its optimization

Zhu, Xiaohua; He, Ling; Liu, Weiji; Luo, Yunxu

doi:10.1016/j.geothermics.2023.102660

Cited by 12 publications

(4 citation statements)

References 37 publications

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“…Figure 4(b) gives the variation curves of shock wave and heat flux during the electric breakdown process. The results derived from this model are consistent with those previously validated by our team [22,23]. Between times t = 0 ∼ 150 ns, the voltage of the pulse rises rapidly, culminating in a peak value.…”

Section: Results Analysis and Discussionsupporting

confidence: 89%

“…In addition, by establishing a numerical two-dimensional model of electric pulse, combining the non-homogeneity of the rock and incorporating the multi-physical field characteristics of the electric pulse rock breaking process, the high-voltage electric pulse rock breaking process is analyzed to obtain and the characteristics of the pulse rise time and breakdown time delay are found [22]. In the study of a three-dimensional high-voltage electric pulse numerical model, various electrode shapes are used to simulate electric pulse rock-breaking, and the adaptability between the structural parameters of the electrode sites and the voltage parameters is found [23].…”

Section: Introductionmentioning

confidence: 99%

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Experimental and numerical simulation research on shock wave rock-breaking by high voltage electric pulse

Liu,

Zhou,

Zhu

2024

Phys. Scr.

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High-voltage electric pulse(HVEP) drilling technology has the advantages of high rock-breaking efficiency, green and non-polluting. Aiming at the importance of HVEP drilling technology in generating plasma channels, plasma shock waves, and rock-breaking pits, this paper carries out multi-physics field numerical simulations and indoor electric pulse breakdown experiments. This paper first constructs a two-dimensional numerical model of rock electric breakdown. The simulation of HVEP rock breaking, plasma channel and plasma shock wave is realized from the five-field coupling and combined with the wave control equations. The effects of different electrode shapes on the plasma channel, breakdown channel and shock wave are analyzed. Then, this paper designed an indoor HVEP rock-breaking experiment to investigate the influence of different electrode shapes on rock breakdown and plasma shock waves. The simulation and experimental results show that the indoor electric pulse breakdown experiment results are consistent with the simulation results; The plasma channels are formed by the ‘electrical damage’ through each other, and the secondary plasma channel is often generated inside the rock. The generation of the secondary plasma channel means that the rock fragmentation depth and the fragmentation area will be increased; The larger the contact area of the electrode bit with the rock, the larger the radius (volume) of the plasma channel and the smaller the amplitude of the plasma shock wave; The quadrangular electrode bits have the best rock-breaking effect and are recommended; The conical electrode bit has the most excellent dispersion in the statistical analysis of the electric pulse rock-breaking effect, and the stability of the rock-breaking effect is poor, so it is recommended to use it together with the composite drill bit; The cylindrical electrode bit has the best aggregation degree of electric pulse rock-breaking and the most stable rock-breaking effect.

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Section: Results Analysis and Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Experimental and numerical simulation research on shock wave rock-breaking by high voltage electric pulse

Liu,

Zhou,

Zhu

2024

Phys. Scr.

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“…and numerically by Rui et al 7 . Fourth, Liu et al 8 . showed numerically that high voltage electric pulses can be combined with rotary drilling by PDC bits to improve the drilling performance.…”

Section: Introductionmentioning

confidence: 99%

Numerical modelling of thermal jet assisted rock cutting with double PDC cutters

Saksala

2024

Num Anal Meth Geomechanics

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Preconditioning of rock for drilling operations is a potential method to facilitate the mechanical breakage and mitigate the tool wear. This paper numerically investigates one such preconditioning technique, namely, the thermal jet assisted rock cutting. For this end, a numerical method for solving the governing thermo‐mechanical problem is developed and validated. The continuum approach is chosen to describe the rock failure, being based on a damage‐viscoplasticity model with the Drucker–Prager yield surface and the modified Rankine surface as the tensile cut‐off. In the damage part, separate scalar damage variables are employed for tension and compression. The cutters are modelled as rigid bodies and their interaction with the rock is modelled by imposing contact constraints by the forward increment Lagrange multiplier method, which is compatible with the chosen explicit time integration scheme. A damage‐based erosion criterion is applied to remove the contact nodes surrounded by heavily damaged elements. The thermal jets are modelled with a moving external heat flux boundary condition. The global thermo‐mechanical problem is solved with a staggered approach explicitly in time while applying mass scaling to increase the critical time step. The novel 3D numerical simulations involving two cutters demonstrate the capabilities of the method with a special emphasis on cutter‐thermal jet configurations. Therefore, the present method provides a potential tool for the bit design in thermal jet assisted drilling.

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“…Hot dry rock (HDR) geothermal energy generally refers to high‐temperature rock bodies between 150°C and 650°C, burial depths of 3−10 km, and internal fluid‐free or small amounts of fluid with good tightness and low permeability 1 . However, dry thermal geothermal resources mainly exist in granite with low permeability, high abrasiveness and high hardness, 2 and deep dry thermal rocks represented by granite have “four high” problems: high geostress, high hardness, high temperature and high densification, and they face many challenges in drilling, fracking, heat extraction and other vital aspects 3–5 . According to statistics, the drilling cost of HDR accounts for 60%−75% of the total cost of geothermal development projects, and the drilling operation time accounts for more than 40% of the total construction time, which seriously restricts the efficient exploitation of geothermal resources 6,7 .…”

Section: Introductionmentioning

confidence: 99%

The mechanism of granite breaking by electric pulse under high temperature and high pressure environment

Liu,

Zhou,

Zhu

2024

Num Anal Meth Geomechanics

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High‐voltage electric pulse drilling technology has the advantages of high rock‐breaking efficiency, and low rock‐breaking energy consumption, which is one of the most promising rock‐breaking methods in geothermal drilling. However, there is insufficient understanding of the mechanism of high‐voltage electric pulse breaking of HDR under high‐temperature and high‐pressure environments (HTHP). In this paper, a numerical simulation model of electric breakdown under HTHP is constructed, and the whole process of high voltage electric pulse rock‐breaking and plasma channel generation is realized from the seven‐field coupling of circuit field, current field, magnetic field, breakdown field, heat transfer field, solid mechanics field and flow field. The temperature changes in the rock during the electric pulse rock‐breaking process were comprehensively analyzed, and the effects of different initial rock temperatures (200°C, 300°C, 400°C) and surrounding pressure conditions (30, 60, 90 MPa) on the high‐voltage electric pulse rock breaking law were considered. It is found that the thermal conductivity of the rock shows an increasing and then decreasing trend as the initial temperature of the rock increases, and that the thermal conductivity has a tendency to guide the development of plasma channels, and the radius of the plasma channels increases with the increase of the initial temperature of the rock. The heat transfer generated by high‐voltage electric pulse rock breaking is mainly in conduction, and the distribution shape of conduction heat is similar to the shape of the breakdown channel. The research in this paper can provide theoretical and technical guidance for developing electric pulse rock‐breaking technology.

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Rock breaking mechanism of electrode bit in heterogeneous granite formation and its optimization

Cited by 12 publications

References 37 publications

Experimental and numerical simulation research on shock wave rock-breaking by high voltage electric pulse

Experimental and numerical simulation research on shock wave rock-breaking by high voltage electric pulse

Numerical modelling of thermal jet assisted rock cutting with double PDC cutters

The mechanism of granite breaking by electric pulse under high temperature and high pressure environment

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