Assembly bottom design hole

If the distance between the bit and the first stabilizer is too large, the bit will begin to tilt upward, and the drop rate will reach a maximum. The assembly may be designed for slight build or drop tendency to counteract formation tendencies. When the distance between the stabilizers increases enough to cause the drill collar sag to touch the low side of the hole, the bit side force and bit tilt reach their maximum build rate for the assembly. They can be used to drill out doglegs and key-seats in hard formations. Bit side force The bit side force is the most important factor affecting the drilling tendency. The bottom-hole assembly BHA can be:

Short sub assemblies are added to the OCB as required to provide landing seats, latch windows, or seal surfaces for the inner core barrel. It is used to equalize the load on the bit; prevent whirl of the lower assembly; minimize bit walk; minimize bending and vibrations that cause tool joint wear; prevent collar contact with the sidewall of the bore-hole; minimize key-seating with differential pressure; restrict lateral movement of the lower BHA as such they lower the strain on the drill collar and BHA connections. Such an assembly would mean that the stabilizers are closely packed: They can be used to drill out doglegs and key-seats in hard formations. Increasing the WOB will bend the drill collars behind the near-bit stabilizer even more, increasing the build rate. Sleeve stabilizers are most economical, but ruggedness often is an issue. Formation dip Formation Rock Properties The BHA design objective for directional control is to provide the directional tendency that will match the planned trajectory of the well.

This is the end of the preview. If the distance between the bit and the first stabilizer is too large, the bit will begin to tilt upward, and the drop rate will reach a maximum. A corresponding pressure drop across the tool would indicate that the tool has fully deployed. Generally, the distance between the bit and the first stabilizer will be approximately 30 ft. Increasing the WOB will bend the drill collars behind the near-bit stabilizer even more, increasing the build rate.