1.Reasonable selection of tricone drill bit types:
(1)Based on the lithology of the formation being drilled, the following principles should be followed when selecting a tricone drill bit type:
a. In the shallow well section, where the rock is poorly cemented and loose, the drilling speed and prevention of mud caking should be the main considerations for selecting a tricone drill bit.
b. In the deep well section, due to its long drilling depth, the penetration rate of the tricone drill bit should be the main consideration.
c. When the outer discharge teeth of the tricone drill bit are severely worn, a tricone drill bit with radial teeth should be selected.
d. In the inclined well section, a tricone drill bit with shorter teeth and less slip should be selected.
e. When using an insert tooth drill bit, a wedge-shaped tooth drill bit should be used.
f. When drilling limestone, a tricone drill bit with double cone teeth or projectile-shaped teeth should be used.
g. When the formation contains more shale or the drilling fluid density is high, a tricone drill bit with greater slip should be selected.
h. For formations such as limestone and sandstone, a tricone drill bit with less slip should be selected.
i. When drilling hard and highly abrasive formations, a tricone drill bit with pure rolling ball teeth or double cone teeth should be used.
(2) The hydraulic parameters of the tricone drill bit should prioritize the use of extended nozzles and non-uniform diameter combination nozzles.
2.Pre-installation check of the tricone drill bit:
(1) Check whether the selected tricone drill bit model and diameter meet the requirements.
(2) Carefully inspect the drill bit threads, welds, and teeth for damage.
(3) Check whether the nozzles are securely installed; rotate the roller bearing to ensure the seal is intact; the pressure compensation system of the drill bit should be intact, and the pressure relief hole should be unblocked.
3.Precautions when installing the tricone drill bit:
(1) Apply thread oil to the drill bit threads after cleaning.
(2) Use a suitable handling tool; do not drop the drill bit into the handling tool.
(3) Tighten according to the specified torque.
(4) The drilling operation should be smooth, and if resistance is encountered, do not apply excessive pressure. For insert tooth drill bits, the drilling speed should be slow to prevent damage to the alloy teeth in hard formations or irregular wellbore sections.
(5) When encountering resistance while drilling, record the depth, the condition of the wellbore, and the time to facilitate identifying the cause of the obstruction and controlling the working time.
(6) When drilling to a distance from the bottom of the well (a single rod), the pump should be turned on, and the turntable should be lowered slowly. Do not pump to the bottom.
(1) The new drill bit should be gently run-in for about half an hour before gradually increasing to the specified drilling pressure. Do not apply excessive pressure to start the turntable.
(2) Pay close attention to the operation of the brake handle, and feed the drill evenly to prevent slipping or jamming accidents.
(3) Analyze the changes in formation characteristics and the working conditions of the tricone drill bit based on changes in the drilling parameters in real-time and adjust the drilling parameters promptly.
5.Determination of the Retrieval Time for Three-Cone Roller Bits
(1) Determine based on the wear of the bearings and teeth. The phenomenon of bearing damage is:
The turntable shows periodic skipping. The skipping is light when the drilling pressure is small, and heavy when the drilling pressure is high.
The drilling speed of the three-cone roller bit decreases, and the pump pressure is normal but the pointer of the weight indicator swings.
(2) The phenomenon of gear jamming is:
The load on the turntable increases, the turntable chain jumps, the square drill rod has resistance, and the turntable stops and reverses.
Drilling speed decreases, and the pointer of the weight indicator swings severely.
(3) The phenomenon of tooth wear (loss) is:
The load on the turntable is reduced.
The square drill rod has no skipping.
The drilling speed is significantly reduced or there is no penetration.
The weight indicator indicates steady without swinging.