Trenchless Technology

NOV 2018

Trenchless Technology is the premier communications vehicle for the trenchless industry. Through our multiple platforms, readers receive insights into the trenchless industry, as well as keep connected to the latest news, products and projects.

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Page 54 of 68

Three-blade PDC bits work well in very soft formations such as clay, sand, and very soft shale. Recommended PSI for three-blade PDC bits is 2,000 to 8,000. Four-blade PDC bits work well in very soft formations and medium soft formations such as soft shale and soft sandstone. Four-blade PDC bits can also handle soft formations such as clay and sand, but the rate of penetration is not as good. Recommended PSI for four- blade PDC bits is 6,000 to 11,000. Five- blade PDC bits work well in medium soft and medium hard formations such as medium and hard shale, soft and medium limestone, sandstone, and silt- stone. Once again, the five-blade PDC bit can handle soft formations such as clay and sand, but the rate of penetra- tion goes further down in those soft formations. Recommended PSI for five- blade PDC bits is 8,000 to 20,000. Six- blade PDC bits work well in medium hard to hard formations such as sand- stone and medium hard to hard lime- stone. Recommended PSI for six-blade PDC bits is 15,000 to 30,000. While there are seven-blade, eight-blade, and ninth-blade PDC bits, they are not usu- ally recommended in HDD applications. Much like the PDC pilot bit, PDC ream- ers work well in similar formations. TCI Tricone Bits The next type of bit that can be used for rock is TCI tricone bits and roller cone reamers. The tricone was invent- ed for the oil field in the early 1900s. Since then, it has been designed and redesigned for every drilling applica- tion, including horizontal directional drilling. (HDD). TCI tricones are very versatile in that there is a tricone for nearly every kind of rock. The key to keeping the best rate of penetration with a tricone is drilling within the pa- rameters the bit is meant for and the formations the bit was designed for. Many times, issues arise with tricones when the bit is over rotated or there is not enough weight put on the bit. With rigs 30,000 lbs and smaller, the biggest problem is not being able to put enough weight on the bit without the rig stall- ing out or increasing RPMs. When the carbides are being worn out before the bearings go out, it is more often than not an issue with not enough weight on the bit. When the bearings wear out be- fore the carbides wear out, it could be that the bit was run correctly. However, if the bearings are failing prematurely, it is often because the bit is being over rotated with high RPMs. Always con- tact the bit manufacturer for correct RPM and WOB to eliminate possible problems with carbides and bearings wearing out prematurely. There are soft formation, medium soft, medium hard, hard, and very hard formation TCI tricones. Recommended PSI for soft formation TCI tricones is 4,000 to 8,000. Recommended PSI for medium soft formation TCI tricones is 8,000 to 15,000. Recommended PSI for medium 54 T R E N C H L E S S T EC H N O LO GY N OV E M B E R 2018

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