Wear mechanisms for polycrystalline-diamond compacts as utilized for drilling in geothermal environments. Final report

Development of a method for predicting the performance and wear of PDC (polycrystalline diamond compact) drill bits

“…Measured friction coefficients between PDC cutters and Sierra White granite are approximately 0.16 under dry cutting conditions and 0.07 when cutting with low-pressure waterjets directed at the cutter/rock interface [19]. The difference in friction coefficient of about 0.09 between the wet and dry cutting conditions is apparently translated to a comparable difference in drag coefficient between the two conditions, as predicted by…”

“…-3 -bit lives and penetration rates two to three times those of roller bits in the same wells [17,20]. Laboratory tests in formations such as Sierra White granite and Nugget sandstone demonstrated that harder formations accelerate PDC cutter wear, although rapid penetration can be achieved before the cutters wear out [10,15,16,19]. Field tests drilling with air in Franciscan graywacke in the Geysers were largely unsuccessful because of problems with cutter studs fracturing off the bit body [15,17].…”

“…The development of an analytical model [22,26,27] for predicting cutter wearflat temperatures in a given drilling environment has allowed experimental data [19,33] to be correlated in a manner that indicates a strong effect of wearflat temperature, Tw, on cutter wear rates [27,29].…”

“…This is caused by the fact that in such cases, the angular transformation converts some of the cutter backrake to a small effective siderake angle. This factor is not significgnt for the relatively small backrake angles generally used in PDC bits (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) .…”

Geothermal COMPAX drill bit development. Final technical report, July 1, 1976-September 30, 1982

“…13-9406. (24) The favorable r e s u l t s of the hot a i r d r i l l i n g experiments were responsible i n p a r t f o r the decision t o attempt t o drill the Geysers very abrasive graywake formation with diamond compact b i t s .…”