INFLUENCE OF COAL ROCK HARDNESS AND CONFINING PRESSURE ON SPECIFIC ENERGY CONSUMPTION OF PDC BIT DURING GAS EXTRACTION BOREHOLE. Global Journal of Advanced Engineering Technologies and Sciences, [S. l.], v. 4, n. 8, p. 1–7, 2017. Disponível em: https://gjaets.com/index.php/gjaets/article/view/163.. Acesso em: 16 jul. 2024.