what is drag bit?
A drag bit is a drill bit usually designed for use in soft formations such as sand, clay, or some soft rock. However, they will not work well in coarse gravel or hard rock formations. Uses include drilling water wells, mining, geothermal, environmental and exploration drilling. Whenever possible, they should be used to drill pilot holes because they produce cuttings that are easiest to log
Historically there were two types of drill bits used in or natural gas drilling rigs , a drag bit and a rock bit:
1.a polycrystalline diamond compact hammer bit( pdc bits) is used for soft rocks, like sand and clay. The drill string is rotated along with pneumatic pressure, and nibs on the bit shear the rock.
2.a deep hole (also called a roller bit ) consists of teeth on wheels which turn as the drill string is rotated. These teeth apply a crushing pressure to the rock, breaking it up into small pieces.
In today's modern industry the two main types of drill bits are now classed as PDC (polycrystalline Diamond Compact) and Roller Cone; although the tri-cone dominates, bi-cone and mono cone bits do exist. Natural and synthetic diamonds are used in coring bits, as well as for very hard rock drilling with mud motors and turbines.drag bit type bits are used for mining and construction and also for oil and gas work over wells.
What PDC bit?
A drilling tool that uses polycrystalline diamond compact (PDC) cutters to shear rock with a continuous scraping motion. These cutters are synthetic diamond disks about 1/8-in. thick and about 1/2 to 1 in. in diameter. PDC bits are effective at drilling shale formations, especially when used in combination with oil-base muds.
Advantages of PDC bits:
Bit Brokers International introduces PDC bits to their line-up of products. These bits are designed for high speed drilling in shale, limestone, and sandstone formations. Unlike roller cones, these PDC bits are a one piece matrix bodies with no moving parts. The fixed-cutters shave away the rock, making it possible to operate with higher rotation speeds more efficiently in consolidated formations.
Bit Brokers offers PDC bits in a variety of sizes and number of blades.
Variables affected PDC bits design
1.Bit body material.
2.Bit profile.
3.Grave protection.
4.Cutter shape.
5.Number of concentration of cutter.
6.Locations of cutter.
7.Cutter orientation.
8.Cutter exposures.
9.Hydraulics.
Roller cone bit A roller-cone bit is adrill bit used for drilling through rock, for example when drilling for oiland gas.
There are three types of roller cone bit:
1.The two cone bit: is used for soft formation only.
2.The three cone bit: is the most widely used.
3.The four cone bit: is used for drilling large hole size.