In oil drilling, the roller cone bit can adapt to the drilling of various formations and is one of the main rock-breaking tools. The movement and force state of roller cone bit when working at the bottom of the well are quite complicated. Therefore, to give full play to the best quality and service life of roller cone bit, it is necessary to strictly abide by the relevant requirements and use the roller cone bit rationally. How to use the roller cone bit reasonably?

1. Reasonably choose the type of drill bit

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.

2. 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.

3. 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.

4. 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.