Trenchless Technology

NOV 2018

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Page 55 of 68

hard formation TCI tricones is 15,000 to 25,000. Recommended PSI for hard formation TCI tricones is 25,000 to 40,000. Recommended PSI for very hard formation TCI tricones is 40,000 plus. Tricones also require a mud mo- tor or rod within a rod system to be run. Roller cone reamers are designed the same way as the tricone pilot bits and have the same characteristics. Air Hammer System Then, there is the HDD air hammer system. The air hammer system is the best system for extremely hard, abrasive rock. The air hammer system uses an air hammer, an air compressor, a hammer bit, and sometimes a support pack. One of the downfalls of an air hammer sys- tem is the air compressor. The air com- pressors are very expensive and use a lot of fuel. However, the air hammer is very fast in hard formations. The bits are fairly inexpensive and have a good life expectancy. Air hammers work well in rock with a PSI of 15,000 plus. Any- thing softer than 15,000 psi, can be an issue and there is often a better bit for the job. There are two different kinds of hammer bits. There are slant face HDD hammer bits that are specifically de- signed for HDD applications. There are also traditional round face hammer bits that were designed for oil and gas drill- ing. Typically, the slant face work better in the HDD application because they are easier to steer. However, there are many drillers that prefer the traditional round face, as well. There are air ham- mer systems for nearly every size rig on the market making a pilot hole as small as 3 in. to as big as 12 ΒΌ in. Rock Head Finally, there is the traditional rock head that does not require a mud mo- tor or rod within a rod system. There are different style rock bits for differ- ent types of formations. Whether the rock be cobble, boulders, consolidated, soft, or hard there is a design of rock bit for that formation. Steering can be an issue with these types of heads especially when there are many boul - ders that the bit tends to bounce off of rather than penetrating. The life of these bits depends on how hard the rock is and whether the correct rock bit is used for the particular formation. While there are different types of rock bits for nearly any kind of rock, this is only suggested to be used for short rock shots and an every once and a while use. If a driller plans on being in rock all the time, it is suggested to use one of the other three types of rock drilling methods talked about in this article. Be sure to do your research on what for- mations you will be in and which rock head will work in those formations. Chester Thomas, JD, is inhouse coun- sel, sales and marketing at Bit Brokers International Ltd. W W W.T R E N C H L E S S T EC H N O LO GY.C O M 55

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