How to Replace a Damaged Cone Drill Bit?

Basic knowledge of roller cone drill bit

After working in the well, the cutting diameter, length, and sharpness of the cutter blade of the roller cone drill bit will decrease, and the ability to break rock will become weaker, resulting in a slower progress. Due to the wear and erosion of the teeth and the damage of the bearings, the roller will rotate inflexibly or jam, resulting in an increase in torque, and if it is not lifted in time, tooth dropping accidents may occur. Diamond drill bits will also slow down the drilling depth due to the heterogeneity of the formation, resulting in cracking, breaking, and dropping of diamond composite pieces on the drill bit. In order to speed up the drilling speed of the entire well and timely replace the old drill bit, how do the drilling workers change the drill bit in the well that ranges from hundreds of meters to several kilometers underground?

Method of replacing roller cone drill bit

When drilling, the power of the drilling rig drives the turntable, square drill pipe, drill pipe, and drill bit to rotate. It is necessary to observe the working condition of the downhole drill bit through the instruments on the ground, and after comprehensive judgment, if it is considered that the drill bit has been worn, it is necessary to immediately stop the drilling and replace the roller cone drill bit. After stopping drilling, the drilling fluid must be circulated for a period of time to adjust the performance of the drilling fluid, carry the rock debris suspended in the drilling fluid out of the ground, and circulate to keep the new wellbore wall stable, while the drilling equipment must also be checked regularly.

The drilling workers use the overhead crane, movable pulley and large hook on the derrick to lift all the drilling tools out of the well according to the height of the derrick, and the drilling pipe in the well is usually composed of two or three drill pipes. After the drilling column is lifted out of the well, the drilling fluid must be continuously injected into the annular space with the drilling pump, aiming to keep the liquid level in the wellbore from dropping, so that the pressure in the wellbore can balance the formation pressure, in order to prevent the wellbore from collapsing or the fluids in the formation from entering the wellbore.

At the same time, pay special attention to stuck drilling due to wellbore contraction, and the operator must strictly control the lifting speed. After lifting all the drill pipes and drill collars in the wellbore, the drill bit that needs to be replaced can also be lifted out at the same time. The workers remove the old drill bit and install a new roller cone drill bit, and then lower it to the well in the original drill pipe order, and then drilling can resume.

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