Abstract As a result of a detailed survey of over 25 novel drilling techniques, a laboratory study of hydraulic jet drilling was made. In initial tests, a cannon was used to fire 1.45-gal water pulses at rocks at pressures up to 25,000 psi. These tests showed that a threshold nozzle pressure must be exceeded before hydraulic jets will drill rock. Water jets having diameters of 0.2- to 1-in. drilled holes with diameters ranging from 0.8 to 4 in. in sandstone and limestone. These holes, which were 1 to 3 in. deep, were drilled in 0.02 to 0.2 seconds. These tests showed that water jets can effectively drill sedimentary rocks. Following these tests, a 2-in.-diameter hydraulic jet drill was tested in a laboratory rig. A high-pressure pump was used to pump water continuously through this drill at pressures up to 13,500 psi. This drill penetrated pressures up to 13,500 psi. This drill penetrated Carthage marble at 180 ft/hour, Indiana limestone at 280 ft/hour and Berea sandstone at 300 ft/hour. These tests showed that a full-scale hydraulic jet drill [3,000 hp] should drill 8-in.-diameter holes in average-strength sedimentary rocks at rates of 200 to 300 ft/ hour, These high drilling rates show that hydraulic jet drills have high potential for drilling oil wells economically. Introduction A survey of over 30 novel drilling techniques revealed that full-scale hydraulic jet drills [also drilled erosion drills] should have high drilling rates in oil wells. These hydraulic jet drills use high-pressure water jets [5,000 to 70,000 psi] to shatter rock and pump the debris from the hole bottom. pump the debris from the hole bottom. Following this survey, we measured hydraulic jet drilling rates and studied variables that affect hydraulic drilling rate. These tests showed that hydraulic jet drills can drill sedimentary rocks at high rates and that they have potential for drilling oil wells economically. Our results, along with a summary of the findings of other investigators, are presented in this paper. BACKGROUND INFORMATION Rock Removal Mechanism A threshold nozzle pressure must be exceeded before water jets will effectively shatter and drill rocks. This threshold pressure increases with rock strength; many water pressure increases with rock strength; many water jets will effectively drill weak materials such as coal or concrete, but will not drill hard rocks such as granite or basalt. Abrasives [e.g., sand or steel shot] have been used in erosion jets operating below threshold pressure.