Yuriy Zhulay

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