Rotary drilling is used to form a deep observation borehole or for obtaining representative samples of rock. The drilling method involves a powered rotary cutting head on the end of a shaft, driven into the ground as it rotates. The system requires lubrication (air, water or drilling mud) to keep the cutting head cool.
There are two types of rotary boring, open-hole and core drilling. Material recovered from open-hole drilling is mixed with the drilling lubricant. It is unsuitable for effective sampling, and it is often difficult to observe and record the strata. Open-hole boring is only suitable for rapid drilling to enable core recovery at a greater depth or for the installation of monitoring wells. Core drilling is carried out using wire-line, double or triple-tube core barrels with diamond or tungsten-tipped core bits.
Advantages of rotary drilling rigs
1.Increased Flexibility
The lightweight modular design makes the drilling rigs easy to install and relocate, in turn, allowing greater operational flexibility for adaptation to different job sites.
2. Higher Automation
Rotary drilling rigs are fully self-propelled hydraulic drilling rigs; some are equipped with computer operating systems. They have many advanced automatic features that allow a high level of flexibility on operations and increased productivity.
3. Faster Drilling
Rotary drilling rigs can be configured with different drill bits according to strata. The long drilling tube is suitable for working in clay soil to speed up drilling. The short drilling tube is suitable in strata containing sand and cobble for better control of drilling speed.
Compared with conventional drilling rigs, a rotary drilling rig has high torque and can automatically adjust itself according to strata. The drilling speed is fast — reaching 10 mph in soil and sand, and 4–6mph in clay soil (3–5 times faster than that of ordinary drilling rigs).
4. High Operational Efficiency
Rotary drilling rigs use drilling muds to lubricate, cool and clean the drilling bit, control down hole pressures, stabilize the hole wall and remove drill cuttings, thus allowing better penetration rates and higher operational efficiency.
5. More Eco-Friendly
Rotary drilling rigs keep the job site clean with low environmental pollution. They generate smaller vibrations and operate with less noise.
