Percussion drilling

percussion drilling

1. SHAH ZEB ALI ROLL NO - 261 UNIVERSITY OF AZAD JAMMU & KASHMIR MUZAFFRABAD

2. DRILLING Drilling  is a cutting process that uses a drill bit to cut a hole of circular cross-section in solid materials . Drilling rigs used to drill water wells, oil wells, or natural gas extraction wells. Drilling rigs can be on land, mobile equipment mounted on trucks, tracks or trailers, or marine-based structures (such as oil platforms, commonly called 'offshore oil rigs).

3. TYPES OF DRILLING Percussion drilling Auger’s drilling Rotary drilling Cable tool drilling Air core drilling

4. Percussion Drilling

5. Percussion drilling Percussion drilling is a manual drilling technique in which a heavy cutting or hammering bit attached to a rope or cable is lowered in the open hole or inside a temporary casing. Percussion drills have been used to drill thousands of feet, though they are generally used for wells from 30 to 250 feet deep. This drilling method has been used in China for over 3000 years.

6. Working of percussion drill The drill involves a heavy steel bit attached to a rope which is lifted, either by hand or by machine, and then dropped to cut the earth. As the bit chops the earth, water is added to the well hole so that the bit makes mud out of the earth it has cut. After the hole is filled with several feet of mud, the heavy bit is withdrawn and a tool called a bailer is attached to the rope and lowered into the hole .

7. The bailer is a hollow tube with a door at the bottom . The door, called a flap valve , opens when it hits the mud to allow the mud to fill the bailer, and then closes to trap the mud inside the tube so that the mud can be lifted to the surface . The tube is emptied at the surface and the procedure is repeated until the hole is clear.

8. Percussion drilling applied, If drilling has to be executed in hard soils, possible containing layers of rubble and/or stones usually percussion drilling is applied. Percussion drilling for instance is applied for research on soil pollution, grain size distribution, general soil classification, profile descriptions, etc.

9. Advantages of percussion drilling: • Simple to operate and maintain. • Suitable for a wide variety of rocks. • Operation is possible above and below the water-table. • It is possible to drill to considerable depths. Disadvantages of percussion drilling: • Slow, compared with other methods. • Equipment can be heavy. • Problems can occur with unstable rock formations. • Water is needed for dry holes to help remove cuttings.

10. AUGER DRILLING

11. Auger Drilling Auger drilling is done with a  helical screw which is driven into the ground with rotation; the earth is lifted up the borehole by the blade of the screw. Hollow stem auger drilling is used for softer ground such as swamp. Solid flight bucket augers are used in harder ground construction drilling. Auger drilling is restricted to generally soft unconsolidated material or weak weathered rock. It is cheap and fast.

12. Method: The cutting tool (known as the auger head) is rotated to cut into the ground, and then withdrawn to remove excavated material. The procedure is repeated until the required depth is reached. Note : This method is only suitable for unconsolidated deposits .

13. ROTARY DRILLING

14. ROTARY DRILLING The rig consists of a derrick, power unit, winch, pump and a drill head to apply high-speed rotary drive and downward thrust to the drilling rods. Primarily intended for investigation in rock, but also used in soils. The drilling tool, (cutting bit or a coring bit) is attached to the lower end of hollow drilling rods The coring bit is fixed to the lower end of a core Water or drilling fluid is pumped down the hollow rods and passes under pressure through narrow holes in the bit or barrel The drilling fluid cools and lubricates the drilling tool and carries the loose debris to the surface between the rods and the side of the hole.

15. The fluid (bentonite slurry) also provides some support to the sides of the hole if no casing is used . There are two forms of rotary drilling, open-hole drilling and core drilling. Open- hole drilling, which is generally used in soils and weak rock, just for advancing the hole The drilling rods can then be removed to allow tube samples to be taken or in-situ tests to be carried out.

16. ADVANTAGES The advantage of rotary drilling in soils is that progress is much faster than with other investigation methods and disturbance of the soil below the borehole is slight .

17. LIMITATIONS The method is not suitable if the soil contains a high percentage of gravel/cobbles, as they tend to rotate beneath the bit and are not broken up. The natural water content of the material is liable to be increased due to contact with the drilling fluid.

18. CABLE TOOL DRILLING

19. CABLE TOOL DRILLING A  cable tool drill is a machine that uses repeated penetration to bore holes into materials such as rock, soil, and cement. It is useful in oil drilling, operating on the first modern wells in North America . Cable tools likely originated from a form of bamboo drill used in China more than 4,000 years ago . It is Used for drilling brine, the bamboo drill could bore up to depths of 3,000 feet (914 m). Although a form of cable drill was invented early on, and was used on projects well into the 1800s, the cable tool drill as we know it today was invented in 1825.

20. METHOD •The cable-tool system was essentially a method of pounding out a hole by repeated blows with a bit attached to a “drill stem”, a heavy length of steel suspended from a wire rope. The drill stem provided the weight to force the bit into the ground, and the hole was kept empty for a little water at the bottom. After drilling a few feet, the bit was pulled out and the cuttings removed with a “bailer ”, an open tube with a valve at the bottom. Steel pipes known as casing , of progressively smaller diameter, were run from time to time to prevent the hole from caving in and to keep back any water flow.

21. AIR CORE DRILLING

22. AIR CORE DRILLING Air-core uses steel or tungsten blades to bore a hole into unconsolidated ground. The drill cuttings are removed by the injection of compressed air into the hole. This method of drilling is used to drill the weathered regolith (loose, heterogeneous material covering solid rock) as the drill rig and steel or tungsten blades cannot penetrate fresh rock. Where possible, air-core drilling is preferred over RAB drilling as it provides a more representative sample. Air-core drilling is relatively inexpensive and is often used in first pass exploration drill programs . Air-core drilling is limited to depths of 50-60 metres and is drilled using a smaller rig known as an Air-core rig. It is possible to use hammer or tri-cone roller for drilling through cap rock at the top of the hole, but not for hammer tails.

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