Olexiy Nikolayev

By Yuriy Zhulay and Olexiy Nikolayev

Sonic drilling is a soil penetration technique that strongly reduces friction on the drill string and drill bit due to liquefaction, inertia effects and a temporary reduction of porosity of the soil. Modern studies to assess the effect of the vibration frequency of the drill bit on the rock fragmentation in experimental and theoretical works on drilling various rocks by the sonic method have shown that vibration frequencies of ~ 1.4 kHz are the most beneficial for ensuring the maximum drilling speed in hard rocks. The above frequencies of excitation of vibrations of the drill bit can be achieved by using a cavitation hydrovibrator. The cavitation hydrovibrator is the Venturi tube of special geometry that converts a stationary fluid (flushing mud) flow into an oscillatory stalling cavitation flow and hydrovibrator structure longitudinal vibrations. The drill bit vibration accelerations are realized in such a drill string, leading to the destruction of rock. Efficient removal of rock particles from the bottomhole is achieved due to high-frequency shock self-oscillations of mud pressure exceeding the steady-state pressure at the generator inlet. The cavitation hydraulic vibrator lacks the main disadvantages of submersible hydraulic hammers.

Part of the book: Mining Technology

By Yuriy Zhulay and Olexiy Nikolayev

Modern progressive technologies use static fluid injection into seams for safe and cost-effective operation of coal seams. However, the deterioration of mining and geological conditions leads to a significant decrease in the efficiency of the process of methane sequestration from coal seams in case of increase in the depth of development of gas-bearing coal seams. This deterioration is due to a change in the stress-strain state of deep rock massifs, their low permeability, strong anisotropy of soft coal, leading to an increase in dynamic manifestations of rock pressure in the form of sudden outbursts of coal and gas, and rock destructions with catastrophic consequences. An advanced technology for hydraulic loosening and recovery of methane from gas-bearing coal seams, based on the creation of hydrodynamic impulses in a well surface and their transformation into mechanical vibration loading to coal seam, was developed. Such impact to the coal mass leads to the development of a system of cracks. As a result, the efficiency of coalbed hydraulic loosening increases, the zones of moistening and unloading of the formation increase, the gas emission of methane is intensified, the level of dust formation and the resistance of coal to cutting during its destruction are reduced.

Part of the book: Drilling Engineering and Technology

By Yuriy Zhulay and Olexiy Nikolayev

A new approach to the numerical analysis of the dynamic interaction of rock and the drill string structure for sonic drilling of wells by using a cavitation hydraulic vibrator is proposed. The approach is formulated on the basis of the developed mathematical model of the “drill string - rock” dynamic system. The parameters of mud oscillations and mechanical vibrations of the drilling tool, as well as oscillation power at contact interaction of the bit with the rock, were determined. It is possible to establish the resonant frequencies of drilling tool mechanical vibrations and the rock, necessary for an increase in rate of penetration. The penetration rate was calculated in two ways: using the concept of hydraulic vibration power and drill vibration power. It has been established that the use of a drilling tool with a cavitation vibrator is more effective compared to other means of exciting the drilling tool vibration load. The intensification of the rock destruction process when drilling with a cavitation hydraulic vibrator is carried out due to an increase in the vibration energy transferred to the rock and a decrease in the energy intensity of the rock destruction process in resonant drilling modes.

Part of the book: Exploring the World of Drilling