A novel tool to improve the rate of penetration by transferring drilling string vibration energy to hydraulic energy

The ultra-high pressure water jet assisted mechanical drilling technology is an effective approach to improve the rate of penetration (ROP), however, due to unreasonable design ideas and low reliability of the existing down-hole supercharger, this technology is not applied widely. To make breakthrough of this technology, a new idea of utilizing the drill string vibration energy to modulate ultra-high pressure jet is first proposed, and a novel down-hole supercharger, down-hole drill string absorption & hydraulic supercharging device (DSAHSD), is developed. The DSAHSD combines the advantages of reducing the axial drill string vibration and generating ultra-high pressure jet to effectively assist rock breaking. When the drilling fluid flows through this tool, part of the drilling fluid will be modulated to the ultra-high pressure jet by periodic compression of piston drove by drill string vibration. Because of hydraulic auxiliary rock breaking of the ultra-high pressure jet, the drillability of rock and the ROP will be enhanced. To analyse the feasibility and influence factors of the tool, mathematical model were established, the results show that the tool could produce more than 140 MPa pressure and the outer pressure increases with the increase of weight on bit and rotary speed. Moreover, there is an optimal diameter of ultra-high pressure nozzle to optimal performance of the tool. This tool has been applied to more than 60 wells in four oil fields throughout China. The results indicate that the maximum density of the test drilling fluid is 1.9 g/cm(3), the single maximum footage is 1480 m, and the operation time of the tool is more than 200 h. Furthermore, the average ROP was increased by approximately 11-831%. In conclusion; the DSAHSD has the characteristics of a simple structure, has a long lifetime, is able to adapt well with existing drilling equipment, and can provide guarantee for wide application of the ultra-high pressure jet technology in oil fields. (C) 2016 Elsevier B.V. All rights reserved.