Nozzle is a dynamic phenomenon arising in the course of drilling, this kind of phenomenon and drilling equipment material relations, mainly the high pressure gas, the existence of stress concentration and soft coal seam a result of the combined action of three factors. When there is no high quality decanter centrifuge material of drilling into the soft coal layer, the bit cutting rotation to produce an impact of coal seam and the crushing force, make the coal crushing, grinding. The fragmentized coal can quickly make gas desorption, borehole surrounding coal fast desorption, increase into the gas drilling to normal several times to dozens times of gas emission, the front and rear drilling a larger gas gradient, thus there is an obvious gas stream, pressure of the gas stream of broken coal particles headwind for ship side pulverization effect, at the same time also continue to drilling surrounding expanding the scope of the impact. The drilling equipment material has a great influence on the implementation of the drilling work. Poor due to the drilling equipment material, appear blocking phenomenon, the gas stream and pulverization of discharging, coal particles are difficult to smoothly to hole further increases the drilling inside and outside of the gas pressure gradient, causes the outflow of gas emission into explosive and formed the orifice.
Whole collapse is the phenomenon of borehole wall collapsed, and down hole drilling equipment material relationship is not very big. Formation of the main reasons of hole collapse has three aspects: (1) coal seam soft, hole wall by vibration over drilling collapse;(2) increase drilling depth, drill bit, the hole is not straight, bent, drilling pipe occur significantly deviate from the central axis swing, destroy the wall of hole;(3) when the orifice 518 centrifuge.
Plugged hole drilling equipment material and coal slag, can discharge phenomenon and the cause of formation plugging holes are: (1) hole discharge and ceaseless stockpile, outside to drilling ahead of coal cinder, coal powder, formation plugging holes;(2) the down hole failure to stop, the side edge collapse, causing residue in normal cleaning eye; (3) The results of the drilling equipment material quality is not high.
Top drill is skid phenomenon, unable to move forward, when drilling bit is often drilling equipment material by the destruction of a kind of state, the pressure of the gas emission, more than or close to feed pressure, temporarily appear bit slippage. Top drill for a long time, because of friction heat can cause fire accident. Stuck drill bit is neither forward nor backward one state, it is mainly due to the failed to exit pipe orifice, broken coal will make sure they skim drill pipe and drill bit, slag discharge, hole dust increase, at this time still drilling, make the wall hole, the increasing range of hole collapse, causing sticking, drill pipe can't.
Spray hole, hole collapse, blocking and sticking, although is different, but sometimes connected between them. Sticking, easy because serious brant screen accident appeared sticking tend to be strongly pulling, hard operation, and will accompany the broken drill rod drilling accidents. So be sure to choose the right drilling equipment material.
Pulverized coal broken when drilling migration, the row of powder wind pressure produced by the positive reaction to the bottom of the hole orifice and pulverized coal with the hole wall of gravity causes reverse friction role. Facing the triangular drill pipe and the education in circular pipe construction force of the drill cuttings were analyzed, and the considering characteristics of fractured media, you can pick and choose the infinitesimal particle are analyzed. Triangular drill pipe due to the edge with the hole wall clearance is small, the operation is equivalent to the hole in the process of pulverized coal to produce a disturbing force perpendicular to the tangent of the borehole circumferential direction, circular pipe due to its own for cylinder, pulverized coal impact around the drill pipe co., LTD. Use high quality drilling equipment material production tools, can better ensure the safety of workers.