THE COST OF DRILLING A GEOTHERMAL WELL IS SIGNIFICANTLY HIGHER THAN THE COST OF DRILLING AN OIL AND GAS WELL AT COMPARABLE DEPTHS.

THE COST OF DRILLING A GEOTHERMAL WELL IS SIGNIFICANTLY HIGHER THAN THE COST OF DRILLING AN OIL AND GAS WELL AT COMPARABLE DEPTHS. THE HIGHER COST IS DUE PRINCIPALLY TO TWOFACTORS: THE HARDNESS OF THE ROCK FORMATIONS BEING DRILLED AND THE HIGH TEMPERATURES ENCOUNTERED IN DRILLING. THESE TWO FACTORS REDUCE THE RATES OF PENETRATION, THEREBY IN- CREASING THE DRILLING COST. A KEY LIMITATION TO UNDERSTAND ING THE REDUCED RATES OF PENETRATION FOR DRILLING GEOTHERMALWELLS IS THE LACK OF AN UNDERSTANDING OF PENETRATION MECHANICS IN GEOTHERMAL ROCKS UNDER DOWNHOLE CONDITIONS. T THIS PROGRAM WILL DRILL REPRESENTATIVE GEOTHERMAL ROCK SAMPLE UNDER SIMULATED DOWNHOLE CONDITIONS WITH FULL-SCALE DRILL BITS AND MEASURE THE PARAMETERS ASSOCIATED WITH DRILLING. SEVERAL ROCK CHARACTERIZATION TESTS SUCH AS MECHANICAL PROPERTIES, POROSITY, GRAIN DENSITY, GRAIN SIZE DISTRIBUTION, PERMEABILITY AND X-RAY DIFFRACTTION, WILL BE PERFORMED ON THE REPRESENTATIVE ROCK SAMPLES. THE DRILLING PERFORMANCE WILL THEN BE CORRELATED WITH THE ROCK PROPERTIESTHROUGH A MATHEMATICAL MODEL. THE GOALS OF THIS PROGRAM AREFOUR-FOLD: 1. ESTABLISH A MATRIX OF ROCK DRILLABILITY FOR AT LEAST FIVE DIFFERENT METHODS OF ROCK PENETRATION I INCLUDING: CRUSHING, SPALLING, SHEARING, EROSION AND SHOCK LOADING. 2. ESTABLISH A DATA BASE OF ROCK CHARACTERIZATION STUDIES FOR GEOTHERMAL ROCKS. 3. DETERMINE THE TEMPERATURE EFFECTS ON THE ROCK PROPERTIES.4. USING THE DATA BASE ON ROCK CHARACTERIZATION AND ROCK DRILLABILITY, DEVELOP A MATHEMATICAL MODEL TO PREDICT PERFORMANCE OF ROCK PENETRATION DEVICES. 2