Diamond-Enhanced Hammer Bits Reduce Cost per Foot in the Arkoma and Appalachian Basins

Abstract

Abstract Polycrystalline diamond technology and down-holehammer drilling have been combined to create a new type of bit. This bit, the diamond enhanced hammer bit, features diamond coated tungsten carbide inserts for improved cutting structure wear resistance. By improving bit life and increasing penetration rates, these bits have been able to reduce cost per foot in the Arkoma and Appalachian Basins. Introduction The use of air as the circulating fluid in drilling has been popular for many years in the Arkoma and Appalachian Basins. The advantages of air drilling are: improved penetration rate, reduced lost circulation, lower mud costs, and less formation damage. Traditionally this has been done with three-cone tungsten carbide insert bits. The recent introduction of tungsten carbide "flat-bottom"percussion bits used in conjunction with a downhole hammer has improved penetration rates in air drilling (ref in The life of these"flatbottom" bits has been limited in most cases by insert wear. In an effort to improve bit life, diamond enhanced inserts were used as the cutting elements in hammer bits. These inserts have proven effective in certain roller cone applications where the wear of tungsten carbide inserts limited bit life (ref. 2). II. DEVELOPMENT OF THE DIAMOND ENHANCED HAMMER BIT Several events led to the development of the diamond enhanced hammer bit for petroleum drilling (figure 1). Firstly, Dr drilling in the oil field was evolving from air roller cone bits, to roller cone bits on "oil field hammers", to the use of solid head ("flat-bottom") bits on industrial hammers. Meanwhile, polycrystalline diamond technology was improving and new applications were being tested. The merger of these separate developments led to the diamond enhanced hammer bit. Air Drilling Air drilling is preferred over mud drilling for several reasons: improved penetration rates, reduced hole problems such as lost circulation and shale sloughing, and reduced mud costs (ref3.). Air drilling is currently done with: roller cone bits and standard rotary drilling, roller cone bits on a down-hole oil field hammer, or"flat-bottom" bits on a down-hole industrial(mining) hammer. The "flat-bottom" Ht on an industrial down-hole hammer typically yields the highest drilling rate of any air drilling system. A study by Sandia National Laboratories (ref. 4) showed that industrial hammers and "flat-bottom" bits drilled twice as fast as roller cone bits with high weight-on-bit and three to six times as fast as roller cone bits on oil field hammers. The industrial hammer operates by supplying air pressure alternately to the top and bottom of a piston. As the piston slides up and down in the hammer it strikes the top of the hammer bit. The kinetic energy is transferred through the bit to the rock fracturing it. The bit itself does not bounce up and down striking the rock. P. 69^