Cyclic shock damage characteristics of electrohydraulic discharge shockwaves

The underwater electrical wire explosion (UEWE) is an appealing source of underwater shock waves (SWs) with a high conversion efficiency from electrical energy to mechanical energy, good repeatability and controllability. Industrial applications are already seen in oil-well unblocking and stratum stimulation, and research is currently underway to apply UEWEs in electro-hydraulic forming, exploitation of unconventional gas and oil resources, etc. The emerging new applications call for a review on UEWE research from the perspective of an efficient SW source. This review paper considers the physical processes and numerical simulation methods, electrical and SW characteristics, and current and potential applications, and provides suggestions for future research directions. The code (XJ_UEWE01) developed by the authors to solve a coupling model of UEWE is included. The paper will provide students and researchers new to this field with an explanation of basic concepts of UEWE and a detailed overview of previous studies, and will aid research on UEWE applications, especially device development and parameter optimization.

“…Xiong et al [169,170] studied the effects of repetitive SWs on cement blocks. The results showed that the cement blocks can be divided into three zones after the SW interaction (i.e.…”

Section: Stratum Stimulation and Fracturingmentioning

confidence: 99%

Electrical wire explosion as a source of underwater shock waves

Shi¹,

Yin²,

Li³

et al. 2021

“…Based on equation ( 4), the attenuation coefficient h can be estimated as 35.83 at R = 65 mm under the discharge circuit parameters and electrode parameters. The relationship between P m and E B is shown in equation (14): is the incident stress, σ R is the reflected stress, and σ T is the transmitted stress. The relationship between the incident stress and transmitted stress is shown in equation ( 15): The transmission coefficient T is shown in equation ( 16) [24]:…”

Section: Time-domain Model Of Ehsmentioning

confidence: 99%

“…Under the action of EHSs, their permeability and porosity increased. Liangli Xiong et al [14] conducted experiments and numerical simulations on a cement block to verify that the repetitive EHS has a cumulative effect on cement samples. Through adjusting the electrical paramet-ers, it can effectively control the damage effect.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical study on the cracking characteristics of repetitive electrohydraulic discharge shock waves

Xiong¹,

Liu²,

Yuan³

et al. 2020

The application of repetitive electrohydraulic shock waves (EHSs) is a developing underwater discharge technology; however, its cracking characteristics on rock under different loading modes are rarely studied. In this paper, an experimental platform of electrohydraulic discharge is built, and test results show that repetitive EHSs can cause obvious macroscopic cracks on samples. A fitting method is proposed for the time-domain waveform of the EHS. The mechanism of the EHS cracking process (liquid–solid interface transmission process, cracking process in rock) is analyzed, and the cracking criterion and fracture zone range of a single EHS on rock are given. In addition, PFC3D simulation is used to establish a three-dimensional numerical model of the test sample under the experimental conditions, and the development characteristics of the damage shape and crack density inside the rock under the action of repetitive EHSs are deeply analyzed. Under different repetitive loading modes with the same loading total energy, the simulation results show the following cracking characteristics: in single-level mode, the crack density is mainly related to the energy of the single loading. The higher the single-loading energy, the more conducive it is to the growth of the number of main cracks, but it will form a crushing zone to cause energy loss; lower single-loading energy is more favorable to the length of main cracks. In the multi-level loading mode, the degraded loading mode has a higher crack density than the upgraded loading mode. Compared to the single-level loading mode, the multi-level loading mode can effectively promote the development of the number and length of main cracks, and effectively reduce the range of the crushing zone. This paper provides theoretical and simulation guidance for the research and application of repetitive EHSs.

“…The PFC can provide theories, methods and tools for elucidating the mechanical properties and microscopic changes of rock before and after the impact of EHS [18]. Xiong et al used PFC 2D to study the cumulative damage caused by EHS to concrete samples and gave a mesoscopic description of the cumulative effects; they found that the degree of damage to cement samples is consistent with the crack density [19]. PFC 3D has been used to study the cracking effect of EHS on three-dimensional (3D) concrete and the cracking effect of EHS under different discharge energies and discharge control modes was simulated [20].…”

Section: Introductionmentioning

confidence: 99%

Study of the fracturing behaviour of an electrohydraulic shock wave in sandstone under static pressure

Xiong¹,

Liu²,

Yuan³

et al. 2021

Self Cite

To understand the application of electrohydraulic shock waves (EHS) in deep rock formations, the fracturing behaviour of repetitive EHS under a static pressure environment is studied in this paper. The static pressure environment of sandstone is simulated and a load model of the transmission wave of EHS at the liquid–rock interface is proposed. Analysis of the spatial distribution, dense zone and fracture zone of microcracks shows that static pressure has a significant inhibitory effect on the formation, distribution and growth of microcracks under repetitive EHS. Compared with normal pressure, cracks in a static pressure environment are mainly concentrated around the well hole, the microcracks are denser and the extension length is shorter. At the same time, the degree of damage is established to evaluate the overall cumulative damage to the sandstone. The coupling relationship between degree of damage, static pressure, discharge energy and discharge times is fitted. The fitting model shows a behaviour of continuous decelerating growth of microcracks, which can be divided into two phases, an initial growth phase and a slow-growth phase. The increase in static pressure mainly suppresses the initial growth phase, and the discharge energy needs to be increased to promote the initial degree of damage and the rate of accumulation of microcracks in the slow-growth phase. The rate of accumulation of microcracks in the slow-growth phase can be controlled through multi-level adjustment of the discharge energy. This paper provides guidance and simulation methods for rock fracturing applications of EHS in static pressure environments.