MONOCONE ROCK BIT WITH JETS AT THE TEETH: DESIGN AND TEST

GEOTHERMAL WELL DRILLING SUFFERS FROM LOW DRILLING RATES AND SHORT BIT LIFE. JET ENHANCEMENT OF ROCK FRACTURE (NOT JUST BOTTOM HOLE CLEANING OR EROSION) REMAINS TO BE DEMONSTRATED WITH A ROLLER BIT. EXPERIMENTS WITH SINGLE INDENTORS SHOW THAT THE PRIMARY ABSORPTION OF ENERGY OCCURS IN THE PULVERIZED ZONE BENEATH THE "TOOTH". ENERGY OF INDENTING IS REDUCED BY A FACTOR OF TWO OR MORE IF THE PULVERIZED MATERIAL IS REMOVED WHILE THE CHIPS FORM. DATA IS LACKING ON THE COMBINED PERFORMANCE OF TEETH INDENTING WITH IMMEDIATELY LOCAL JETTING. CONSTRUCTION AND OPERATION OF ROLLER BITS LIMIT DESIGN OPPORTUNITIES FOR SYNERGISM OF TEETH AND LOCAL JETS. ONE OBJECTIVE IS TO DEMONSTRATE ENHANCED PENETRATION OF TEETH HAVING PROXIMATE JETS THROUGH THE ROLLER CONE. A ROLLER BIT IS THE BEST MEANS TO DEMONSTRATE REPEATED ATTACK ON A PROGRESSIVELY REMOVED ROCK SURFACE (VERSUS SINGLE INDENTORS). A SECOND OBJECTIVE IS TO DEMONSTRATE A CONFIGURATION THAT HAS TOOTH-LOCAL JETS, AS WELL AS FEATURES FOR GEOTHERMAL DRILLING. THE CONCEPT IS A MONOCONE BIT HAVING MORE BEARING AND SEAL CAPABILITY AND HIGH-SPEED CAPABILITY FOR DOWNHOLE MOTORS. IT IS INTENDED FOR JET HYDRAULICS BELOW 6 KPSI. THE BIT WILL BE DESIGNED AND CONSTRUCTED AT FOSTER-MILLER AND TESTED AT THE COLORADO SCHOOL OF MINES' INSTRUMENTED ROTARY RIG. IT WILL INCLUDE SEALED BEARINGS, A BODY-TO-CUTTER ROTARY SEAL FOR JET FLUID, AND CARBIDE TEETH. THE DESIGN WILL BE SUITABLE FOR ADVANCED SEALS AND MATERIALS, BUT THEY WILL NOT BE INCLUDED. RESULTS WILL BE DATA FOR ROLLER BIT PENETRATION WITH AND WITHOUT JET FLOW AT THE POINT OF TOOTH CONTACT, A PRELIMINARY DESIGN OF SUCH A BIT FOR GEOTHERMAL DRILLING, AND AN EVALUATION OF REDUCTION IN DRILLING COSTS USING EXISTING MODELS.