**1. Introduction**

Sonic drilling is an effective method for sampling soft soils without disturbance, which can also be used for rapid drilling of bedrocks using vibration shock technology with rotary drilling [1]. Hydraulic hammers are of a dynamic type, operate on the energy of the flushing mud. Their operation principle is based on the effect of a water hammer as a result of interrupting the flow of fluid [2]. The main disadvantages of submersible hydraulic hammers are still:


• negative impact of pressure oscillations to the mud pump, causing increased wear of its parts and deteriorating drilling efficiency due to the unambiguous dependence of the bottomhole power on the pump characteristics [3].

At present, researchers from various countries continue to work on improving the characteristics of hydraulic hammers. For example, in the last decade in the Russian Federation, research has carried out on volumetric hydropercussion machines [3]. The foundations of the theory have been developed and original hydraulic shock and distribution devices have been created. Their peculiarity lies in the presence of a hydraulic accumulator, which complicates the design, especially for significant depth drilling.

Analysis of recent studies and publications indicates the trend of using hydrodynamic cavitation as a source of vibration loading on the drilling tool to increase the drilling speed in hard and super hard formations. Such studies are presented by authors from different countries at conferences on geomechanics and well drilling. So, for example, in the works [4–6] in the process of experimental studies it was found to improve the operational characteristics of the drill bit. This was achieved by intensifying the removal of crushed material from the contact zone between the surfaces of the bit cutters and the rock during drilling due to cavitation effects in the high-pressure flow of the drilling fluid in the bit nozzle. It was found that for drilling with a cavitation impulse tool more efficient cutting of the rock and transportation of drill cuttings occurs, and friction in the drill string is also reduced.

Possibilities of increasing the profitability of well construction using pulsating jet technologies in future designs of the drill string with the optimization of the frequency and amplitude effects of the bit, taking into account the lithology of drilled rocks, are given in [7]. It was shown, "this could lead to faster and more efficient drilling, which will reduce drilling costs and make more oil and gas wells profitable".

In the last decade, researchers from China have been intensively engaged in the creation of a new cavitating drill bit [8]. This was due to the need to overcome a number of problems in its western region during exploration and construction of superdeep wells with the depth ranging from 2000 m to 6000 m. In particular, the rate of penetration (ROP) of wells and the rate of development of new fields in these difficult geological conditions decreased significantly, and the cost of drilling increased dramatically.

To overcome the above problems, a new drilling tool was developed with the installation of a hydraulic impulse generator of a cavitation jet. Tests of such a generator have shown that at a flow rate of flushing fluid from 32 *l/s*, it implements fluid pressure oscillations with amplitude range *∆Р* from 2.1 to 2.2 MPa and a fundamental frequency up to 10 Hz. Field experiments conducted in oil fields throughout China on more than 100 wells with the maximum depth of 6162 m have shown that drilling with this tool increases the ROP by 16 ÷ 104%. This is due to the pulsation of the jet, cavitating erosion and the effect of local negative pressure, as well as an improvement in the cleaning efficiency of the bottomhole [9, 10].

At the same time, studies to assess the effect of the vibration frequency of a drill bit on rock fragmentation in experimental and theoretical works on drilling various rocks by the sonic method showed that vibration frequencies of 1.4 kHz [11] are the most beneficial for ensuring the maximum drilling speed in hard rocks.

At the end of the last century (in the 80 s) the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine (ITM NASU) together with the 'Geotechnika' special design bureau (Russia) created a new scientific direction in the development of submersible percussion machines using the effects of hydrodynamic cavitation [12]. The main goal of this direction was the creation of a new method of dynamic loads on the drill bit, allowing to eliminate the disadvantages of existing hydropercussion machines. This method was implemented in the development of a drill string with a cavitation hydraulic vibrator.

*Sonic Drilling with Use of a Cavitation Hydraulic Vibrator DOI: http://dx.doi.org/10.5772/intechopen.100336*

Analysis of the latest publications on the study of promising devices that intensify the technological process of drilling exploration and production wells shows that the drilling technology using the cavitation hydraulic vibrator has a number of advantages. It lacks the main disadvantages of submersible hydraulic hammers [3] and impulse devices [10]. Cavitation hydraulic vibrator does not require additional energy sources and does not contain moving parts, it is easy to manufacture and fits organically into existing equipment without affecting the pump, since drill mud pressure oscillations are not transmitted above the place of the vibrator installation.
