Analysis and preventive measures for drilling accidents caused by kilometer drilling rig jamming

Analysis and preventive measures for drilling accidents caused by kilometer drilling rig jamming
introduction
In the mining process, conventional drilling machines have insufficient drilling capacity, short drilling length, and poor directional effect. Generally, construction can only be carried out after the formation of the roadway, and the pre extraction period is very short, resulting in the inability of mine gas extraction to meet the needs of safe production in the mine. For this purpose, kilometer drilling machines and supporting equipment can be used in the coal mining process for underground directional long drilling and branch drilling construction, which can extract gas and detect geological formations. Kilometer drilling machines are widely used in many coal mine production processes, but there are also some defects in their use. Drill jamming accidents are the most common. In the process of coal mining, it is necessary to analyze the drill jamming accidents of kilometer drilling machines, timely identify the causes, and solve problems to prevent serious safety accidents.
1、 Analysis of the stuck drilling accident of the kilometer drilling rig
（1） Accident Overview
This article takes a coal mine as an example to analyze the stuck drilling accident during the use of the kilometer drilling rig. During the mining process of the coal mine, due to technical and geological reasons of the coal seam, there were four incidents of drill jamming and one incident of drill dropping.
The first time the drilling rig got stuck, it penetrated to a depth of 60m. At that time, the drilling rig could not rotate, and the construction personnel recorded the accident. Based on the situation at that time, due to the fact that the drilling on the construction site was an uphill hole, the pressure inside the hole was relatively high. At that time, the technical personnel adopted a high flow rate to send water into the hole and then adjusted the water flow to the minimum, allowing the water to slowly flow out and flush out the coal slurry at the blocked location inside the hole. Then, the drilling rig was slowly rotated, and finally the drill rod was successfully pulled out.
The depth drilled during the second stuck drilling was 280m, and the drilling rig could not continue to rotate. The technicians used the same method based on previous situations, but the drilling rig still could not rotate. Later, the technicians adopted the method of enlarging the hole and pulling out the drill rod.
When the drilling rig got stuck for the third time, the drilling depth was about 580m. Due to the deep drilling depth at this time, the construction team discussed and set multiple plans. Finally, they chose to use salvaged drill rods and apply butter inside the salvaged drill rods to reduce the friction between the salvaged drill rods and the stuck drilling rig drill rods in the hole. After ten hours, the drill rods were pulled out.
The depth drilled during the fourth stuck drill was 368m. Based on the previous stuck drill accident of the drilling rig, the construction technical team successfully pulled out the drill rod after integrating multiple solutions.
（2） Analysis of the causes of drilling rig jamming accidents
The main approach to analyzing the stuck drill accidents that occurred in the production of the coal mine is to start with the records of drilling rig construction, and conduct a detailed analysis of various drilling rig stuck problems recorded in the records. It was found that drilling rig stuck is mainly related to parameters such as water pressure inside the borehole, coal seam roof and bottom conditions, water flow rate during drilling, and drilling rig thrust pressure. Under normal circumstances, when the drilling depth of the kilometer drilling rig does not exceed 500m, if the coal quality is relatively hard, the reading of the water pressure gauge during the drilling process will generally remain between 300-400pis, and the normal water flow rate is per minute
200L, the pressure gauge reading of the drilling rig's propulsion is between 1800 and 2000pis. However, if the drilling reaches the top or bottom plate during the drilling process, the water pressure will suddenly increase, and the pressure reading is generally between 400 and 500pis. The propulsion pressure of the drilling rig will increase by more than 2000pis, but the water flow rate will always be normal. If the drilling depth is deeper, exceeding 600m, the water pressure will also increase as the drilling depth increases. Generally, when the drilling depth is between 600-700m, the water pressure can reach 500pis. During the drilling process, stuck drill refers to the situation where the coal slurry in the borehole is not discharged in a timely manner, resulting in the drill rod being stuck and unable to rotate. If the water pressure increases to 600 pis during the drilling process, it is easy for the coal slurry to lock the drilling rig. At this time, drilling should be stopped immediately to prevent further drilling from bringing excessive pressure to the drilling rig and causing the drill bit to break. After stopping drilling, the drill rod should be pulled out of the borehole and the color of the water outlet should be observed to determine whether the stuck position is coal slurry or rock. If the color of the water outlet is black, it indicates that the borehole is blocked by coal slurry and needs to be cleaned to flush out the coal slurry. If the color of the water outlet turns white, it indicates that the rock on the top or bottom plate has been reached.
Through practice, it has been found that the more complex the structure of the coal seam and the more soft coal there is, the more likely it is to collapse during drilling. The excessive pressure on the coal seam can easily cause deformation after drilling, resulting in the inability to discharge coal slag and ultimately leading to drilling jamming. In addition, during drilling, if the drilling speed is too fast, the coal slag cannot be washed out by the water flow in a timely manner. If there is a sudden power or water outage during the drilling process, and the time is long, it will also cause the coal slurry to be blocked, resulting in drilling jamming.
2、 Preventive measures for stuck drill
Drill jamming is a very common problem in the process of coal mining. When drill jamming occurs, it should be dealt with in a timely manner by pulling out the drilling rig. At the same time, in the daily management process, it is necessary to strengthen the prevention of drill jamming accidents and improve the drilling level of the drilling rig from a technical perspective.
（1） Carefully analyze the geological conditions of the coal seam
In coal mining, it is necessary to understand the basic situation of the coal mine, the distribution of soft and hard coal seams in the coal seam, and then scientifically and reasonably design the boreholes through geological specifications and drilling records, so that the boreholes can avoid soft coal seams as much as possible and drill in hard coal as much as possible.
（2） Avoid coal seam pressure zones
Excessive pressure can cause deformation of the borehole, blockage of coal slag, and inability to flow out in a timely manner, resulting in stuck drilling. Therefore, during the drilling process, it is necessary to avoid the coal seam pressure zone and separate the mining face from the excavation construction pumping location to prevent the collapse of the borehole due to the influence of dynamic pressure from the mining face during the drilling process.
（3） Improve management system
During the use of the drilling rig, the low technical level and non-standard operation of the operators are also the main reasons for the problem of stuck drilling. During the drilling process, it is necessary to continuously improve the management system, which can be approached from the following aspects:
Firstly, strengthen personnel training and improve the quality of drilling personnel. The drilling depth of the kilometer drilling rig is very deep, but there are also significant safety hazards. During the drilling process, it is necessary to improve the quality and safety awareness of technical personnel, strengthen the training of technical personnel, so that they can master the use of the kilometer drilling rig, operate according to regulations, and reduce the problems caused by misoperation.
Secondly, increase the intensity of rewards and punishments. During the drilling process, due to the negligence of technical personnel, drilling accidents during the construction process are quite serious. Therefore, coal mining enterprises must improve the reward and punishment system. For safety accidents caused by personal reasons during the construction process, strict punishment must be imposed. For technical personnel who have had zero consecutive accidents, rewards can be given. Through a clear management system of rewards and punishments, technical personnel can be guided to form a good sense of responsibility and quality awareness, reducing the incidence of accidents during the drilling process.
Thirdly, strengthen the management of construction sites. During the drilling process, it is necessary to actively improve the management system of the construction site. Safety management personnel should be equipped at the construction site to promptly supervise the construction process
The handling of drilling accidents that occur on site should be carried out, and a three-level management system should be implemented. The team leader is fully responsible for the entire operation process, the drilling rig operator is responsible for drilling rig operation, data analysis, and problem handling, and the auxiliary worker mainly plays an auxiliary and coordinating role, providing services for the drilling rig operator. The three parties should supervise and remind each other. Once signs of drilling are found, the drilling rig operation should be stopped in a timely manner, and the drill rod should be gradually pulled out.