Rational use and procedure selection of diamond all-round bit

Company News by: 2022-03-25 11:31

Due to its brittleness, poor impact resistance and high thermal sensitivity, diamond drill conditions are much stricter than other drill bits.

1. Requirements for hole bottom cleaning

Before running a diamond bit, a carbide bit with a similar shape to the diamond bit with a powder tube must be used for intervention. With water to the hole bottom of the large debris, broken metal and other things rushed up, sink in the powder tube.

2. Initial grinding of new drill bit

A new diamond bit must be selected with a diameter smaller than that of a non-diamond bit and run - in drilling is performed. The initial rotational speed should be 40 ~ 50r/min, and the initial woB should be 1/8 of the normal woB. About 0.15 ~ 0.2m will be drilled before turning to normal drilling.

3. Parameter selection for normal drilling

(1) Formation lithology and bottom-hole lifting force caused by hydraulic flushing should be considered to determine woB. The maximum specific pressure at the bit lip is 6.9MPa in soft formations. In hard strata, due to the small cutting depth of diamond, small contact area with rock, and in hard strata, diamond is easy to fracture due to overload, so it is recommended to use a small specific pressure, generally 5.1mpa. The woB values of diamond bits with different diameters for different formations can be selected as shown in Figure 5-14. The weight on bit for normal drilling should be set at the lower limit of the curve. The weight on bit increases gradually as the diamond becomes dull, but should not exceed the upper limit of the curve. The actual weight on bit obtained by estimating or checking the curve should be added to the effect of buoyancy and liftoff forces in the hole.

(2) Rotational speed After the bit runs in, the ideal rotational speed should be as high as possible in order to give full play to the benefits of diamond drilling. While 150r/min is considered safe, an increase to 300r/min is more effective if formation conditions, pipe quality and equipment capacity allow. Diamond bits combined with turbine drills have been successfully used in the range of 600 ~ 1 100r/min with good results.

(3) Pump volume First of all, the pump volume should meet the requirements of the minimum reflux speed in the annular space, and at the same time to ensure the cleaning of the bottom of the hole and the cooling of the drill bit needs. Figure 5-15 shows the recommended pumping ranges for different diameters, with the lower limit for high-density mud and the upper limit for low-density mud