A Novel Tool To Improve the Rate of Penetration–Hydraulic-Pulsed Cavitating-Jet Generator

Abstract

On the basis of the analysis of the jet-modulating mechanism, a novel tool-a hydraulic-pulsed cavitating-jet generator (HPCJG)is designed to further improve the rate of penetration (ROP). The HPCJG combines the advantages of a pulsed jet and a cavitating jet. When the drilling fluid flows through this tool, the fluid will be modulated to the pulsed and cavitating jet by application of the impellers and by entering into the self-resonant chamber. During this process, a pulsed cavitating jet is formed at the outlet of the bit nozzle. Because of jet pulsation, cavitating erosion, and the local negative-pressure effect, the cleaning efficiency of the wellbottom cuttings and the ROP will be improved. Laboratory and oilfield tests have indicated that the pulsed-pressure amplitude and the pressure drop of the generator increase with the increase of the flow rate. However, the frequency of the pressure pulsation is invariable in this process. This generator has been applied to more than 100 wells in eight oil fields throughout China. The results show that the maximum density of the test drilling fluid is 1.93 g/cm 3 , the maximum test-well depth is 6162 m, and the operation time of the generator is more than 230 hours (the maximum operation time recorded was more than 520 hours). Furthermore, the average ROP was increased by approximately 16.7% to 104.4%. In conclusion, the generator has the characteristics of a simple structure, has a long lifetime, is able to adapt well with existing drilling equipment, and can provide a safe and efficient drilling technique for deep wells.

Characterization of a Pulsating Drill Bit Blaster

“…49 below could be altered so that its geometry amplifies the pulsation similarly to Fu et Al. (2012) and Cui et al (2013) both of which employed the use of a resonant chamber.…”

“…11 (Fu, et Al., 2012). The pulsation was increased due to cavitation behind the impeller blades creating localized impact pressure of 8.6-124 times the pressure of the free jet as the cavitation volumes collapsed.…”

“…The pulsation was increased due to cavitation behind the impeller blades creating localized impact pressure of 8.6-124 times the pressure of the free jet as the cavitation volumes collapsed. The pressure in the drillstring was measured near the surface of the well and pressure fluctuation amplitudes of 250-350 psi at around 10 Hz recorded (Fu, et Al., 2012). The design was tested in ultra-deep wells (5000m-7000m) and a 10.1-31.5% increase in ROP and average of 29.1% increase bit footage life recorded.…”

“…Figure 11: Cavitating impeller pulsation design (Fu, et al, 2012) It is important to note that cavitation alone, whether at the nozzle or above the bit, has been shown to not always lead to improved cutting efficiency or an improved ROP. Instead, the drilling system must be compliant to the vibrations produced by the tool in order to intensify the natural displacement vibration of the compliant element (Badapour, 2014).…”

Research on the modulation mechanism and rock breaking efficiency of a cuttings waterjet

“…1,2 Therefore, it is urgent to seek available cost-effective rockbreaking methods for improving the penetration rate in hard formations of deep wells. 3,4 A high-pressure waterjet is considered one of the most promising assisted rock-breaking technologies. 5 To overcome the problem of tool wear caused by high pressure and take full advantage of hydraulic energy at the bottom, several types of waterjets, including pulsed, 6 cavitating, 7 and abrasive waterjets, 8 have been proposed.…”