1. Equipment related factors
One is the impact of drilling pressure on drilling speed. Drill pressure refers to the pressure applied by the drill bit to the medium after subtracting various resistances from the feed force output by the drilling rig. Practice has shown that under certain drilling conditions, the drill pressure is linearly related to the drilling speed over a large range. When the drill pressure value is before point 1, the drilling speed is too slow due to the low pressure. After point 2, the drill pressure is too high, and the drill bit does not fully cut the medium, resulting in increased slag discharge, poor cooling effect of the drill bit, increased wear, and worse drilling effect.
The second is the influence of rotational speed on drilling speed. The rotational speed output by the drilling rig represents the speed at which the drill bit cuts the medium at the bottom of the hole. In theory, the drilling speed increases with the increase of rotational speed, but in practice, the two are not linearly related. The drilling speed has a critical value, and beyond this value, it will not increase due to the increase of rotational speed, but will instead decrease. The main reason is that the drill bit has a short interaction time on the surface of the medium, which affects the depth of penetration. At the same time, the high speed of rotation leads to an increase in the temperature at the bottom of the hole, and the wear of the drill bit intensifies. The relationship between drilling speed and rotational speed in media with low abrasive properties is basically linear. The relationship between medium drilling speed and rotational speed gradually slows down with increasing rotational speed, and the magnitude of the decrease in drilling speed varies with rock type, drilling pressure, and drilling tool shape.
2. Objective external factors
Firstly, different materials and sizes of drill bits require different matching speeds when drilling into different media, otherwise the efficiency cannot be fully utilized. For example, a 94mm diamond surface mounted drill bit generally requires an output speed of 260-600r/min, while a impregnated drill bit requires an output speed of 350-700r/min. The selection should be based on the characteristics to improve efficiency;
Secondly, during the construction of a fully hydraulic drilling rig, pressure air or pressure water is generally used to flush the bottom of the hole and discharge drilling debris. Each medium has its own advantages and disadvantages, and can be selected according to the needs. However, when using pressure water slag discharge for drilling at a large angle (+30 ° or more), the water in the drill rod will flow back due to gravity. It takes a long time to send the water to the bottom of the hole after adding the drill rod, and more time is needed for deep hole drilling, which affects the drilling speed. Therefore, if conditions permit, a one-way check valve can be added between several drill rods to ensure that the slag water will not flow back and improve the drilling speed;
Thirdly, the quality and flow rate of the flushing fluid from the drilling tools have a certain impact on the drilling speed. According to publicly available data, the viscosity of the flushing fluid decreases, and increasing the flushing fluid flow rate also increases the drilling speed. Therefore, selecting the appropriate flushing fluid can improve the drilling speed.
