Special consideration was given for the abrasive fracture formation, high mud weights, and extra wear to the shoulder and gage of the bit associated with a horizontal application We chose 9 stones per carat, versus 12 stones to increase penetration in the high? 15 lb drilling fluid The best quality natural diamonds were used (J stones) for their abrasion resistance. A T.F A. of.45 was designed to provide a 250 psi pressure for proper bit cleaning and cooling. This would also give us a large enough pressure drop so we could adequately monitor the standpipe for fluctuations, which might indicate a jammed core barrel.