A roller cone bit is a drilling equipment widely used in oil, natural gas, and metal mining. Its high efficiency, stability, and low cost make it popular in many industrial fields. Nevertheless, unlocking the full potential of roller cone drill bits hinges on their proper utilization.
Understand the basic structure and working principle of roller cone bits
The premise for the rational use of roller cone bits is to have a deep understanding of them. Roller cone bit consists of more than 20 parts such as cutting structure, bearing structure, locking element, oil storage sealing device, and nozzle device. When it is working, by providing it with sufficient axial pressure and rotary torque by drill, the roller cone bit drills and rotates on the rock at the same time and generates static pressure and impact dynamic pressure on the rock to realize rolling at the bottom of the hole. The continuous extrusion and cutting impact break the rock.
Reasonably choose the type of drill bit
First, choose the appropriate roller cone bit type based on your specific drilling needs.
According to the lithology of drilled formation
a. In the shallow well section, the main consideration is the drilling speed of drill bit and the prevention of mud pack.
b. In the deep well section, because of the long hoisting, the main consideration is the feed rate of drill bit.
c. When the outer carbide of drill bit is seriously worn out, it is advisable to choose a drill bit with a gauge cutter.
d. In the inclined well section, it is advisable to choose a drill bit with a small slip and many carbides.
e. When selecting an insert drill, it is advisable to use a chisel bit.
f. When drilling limestone, it is advisable to use conical bits.
g. When there are more mud shales in the stratum or the drilling fluid density is higher, it is advisable to use a drill bit with a larger slip volume.
h. When drilling hard and highly abrasive formations, it is advisable to use a drill bit with a smaller slip volume.
i. When drilling hard and highly abrasive formations, it is advisable to use pure rolling buttons and double conical bits.
Furthermore, it’s imperative to consider factors like the material composition and the heat treatment process employed in manufacturing the drill bit. These considerations are essential to guarantee the requisite hardness and wear resistance of the drill bit.
Optimize drilling parameters
Proper use of roller cone bits also requires optimization of drilling parameters. It includes drilling pressure, rotational speed, mud displacement, etc. The drilling pressure is a critical factor affecting the cutting effect of the roller cone bit and should be adjusted according to the formation conditions and drill bit type. The rotation speed, likewise, should be chosen based on the drill bit type and formation hardness to ensure the stability and cutting efficiency of the drill bit. The mud displacement should ensure that the rock chips generated by cutting can be removed in time to avoid the accumulation of rock chips affecting the drilling efficiency.
Checking the drill bit before entering the well
① Check whether the selected drill bit type and diameter meet the requirements.
②Check carefully whether the drill bit is in good condition in terms of the wireline, welding seam, and carbides.
③ Check whether the nozzle is firmly installed and the water hole should be unblocked. Turn the cone by hand, and bearing seal should be intact. The pressure compensation system of drill bit should be intact, and the pressure relief hole should be free of blockage.
Precautions for drill bit into the well
①Clean the drill bit thread and coat it with special oil.
②Choose a suitable loader, and don’t jerk the drill bit into the loader.
③Tighten up according to the specified torque when fastening.
④The drill should be operated smoothly and not pressed hard when it is blocked. The drill bit should be slow to avoid breaking the carbide in hard strata and irregularities in the borehole.
⑤ When drilling down the borehole, write down the depth of the well, the situation of the borehole, and the time, so that you can judge the reason for the obstruction and control the working time.
⑥When drilling to a certain distance from the bottom of well, turn on the pump and turn the turntable to put down slowly, and it is strictly forbidden to turn on the pump at the bottom.
Precautions for drilling
① New drill bit should be lightly pressed for about half an hour before gradually increasing to the required drilling pressure, and it is strictly forbidden to start the turntable under pressure.
②When operating the brake crank, concentrate your energy and send the drill evenly to prevent slipping and stalling accidents.
③Analyze the change of lithology and the working condition of drill bit at any time during drilling according to the operation of drill bit, and adjust the drilling parameters in time.
Regular maintenance
Regular maintenance is indispensable to prolong the service life and enhance the performance of a roller cone bit. It includes cleaning drill bits, replacing severely worn cutting edges, checking bearings and seals, etc. In addition, the torque and pressure of the drill bit should be adjusted by the formation conditions and drilling parameters to minimize drill bit wear.
Strengthen on-site monitoring
When drilling, strengthen on-site monitoring to find and solve problems in time. For instance, if significant wear on the cutting edge is identified, it is crucial to promptly replace a new one. When damage to bearings or seals is detected, replace the parts with new ones in time. Furthermore, it is essential to conduct regular checks on parameters such as the torque and pressure of the drill bit to ensure that they consistently fall within the normal range.
Conclusion
The rational use of roller cone bits is not only related to the efficiency and cost of drilling operations but also the key to ensuring the smooth progress of the project. By deeply understanding the structure and working principle of roller cone bits and taking various measures, we can maximize the performance advantages of roller cone bits, extend their service life, and reduce the overall cost of use. At the same time, this also requires our operators to have rich professional knowledge and a high sense of responsibility, always pay attention to the operating status of the drill bit, and adjust and optimize the use strategy in time. Only in this way can we achieve efficient, stable, and sustainable drilling operations in a complex and changeable drilling environment and contribute more to the development of fields such as oil exploration, geological surveys, and mining.
