24 NOVEMBER 2023 WorldWide Drilling Resource® The HPI-Process Powered by the JET Master: Part 1 A scientifically proven, high-efficiency method to develop and rehabilitate wells by Don Baron, Managing Director U.S./Canada, JET Master by Etschel Brunnenservice and Leonard Etschel, Vice President, Etschel Brunnenservice GmBH Since the early 1960s, high-pressure water-jetting meant 3/16-inch up to 1/2-inch-diameter drilled holes into a coupling with a smaller hole in the bottom and later the design included prefabricated nozzles, normally four per single row. At a maximum output of 100 gpm (gallons per minute) and 250 psi discharge pressure, each nozzle would have a jetting velocity in the range of 200 fps (feet per second). Attached to drill rod, these tools may then rotate 10-50 rpms while traveling slowly up or down selected well screen intervals. The secret to a successful well cleaning was to simultaneously jet and pump the well, thus removing solids and drilling fluids from the initial drilling process. If one injects water into the well, the well’s static water level rises thus creating a positive hydraulic head or mound effect which tends to push water away from the well screen assembly and out into the formation. When a depression pump is installed above the jet and is pumped at a rate greater than the injection rate, those well screen flows will reverse so bentonite and solids will be drawn out of the formation and filter pack, and into the wellbore pump. With the pumping water level below the original static water level, more water will be discharged than injected. The problem which may arise is the competition for space within the borehole. In some cases, a drill rod inside a well casing may not allow enough space for the submersible pump and cable wire or even a one-inch-diameter air line pipe. In other cases, a one- or two-inch air line pipe may be the only solution for that confined space. Depending upon static water level and anticipated pumping rate, the airlift method may not be practical. Many times, the water-jetting operation did not have any water withdrawal method so solids returning into the well would be removed after the jetting tool was extracted. This jetting method may be adequate, but not ideal. Without a means to extract solids, the jetting device with sediment-filled water in the screen area may have acted like a liquid sandblaster to the metal screens and casings causing slot erosion and continued sand pumping problems due to well screen and pipe damage. Within the last 15 years, a subtle change has been made in industry terminology. The former high-pressure water-jetting term is being relegated to jetting with water and “high-velocity water jetting is a relatively new development technique . . . where high pressure water jetting now means pressures up to 10,000 psi and sometimes more and jetting velocities up to 1,000 fps” (Groundwater & Wells; 3rd Edition, 2007, p. 519). This jetting method may have the power to penetrate the filter pack, break down the skin layer (barrier or mud wall) on the face of the borehole, and penetrate into the mud-invaded zoned (invaded into aquifer before the mud cake was formed) and into the aquifer. The high-pressure water jetting beam may now be from a self-rotating nozzle for continuous horizontal water jetting into the well screen or a stationary jetting nozzle assembly. The 10,000 psi pressure value is gauge pressure and represents pressure inside the jetting tool assembly and piping equipment. The pressure at the nozzles may be less than this gauge pressure due to differential head pressure from submergence and friction losses depending on the hose or pipe length. In the late 1990s, people in Germany claimed to have the most efficient technology. The DVGW (Germany association for gas and water) reacted and invited all companies to a test site at the German Groundwater Research Center in Dresden. A test stand was built with well screen, gravel pack, and aquifer. Sensitive transducers were added to screens, the middle of the gravel pack, borehole wall, and another three in the aquifer. The penetration depths were measured to determine effectiveness through all these barriers into the aquifer. Any velocity variables were also measured. The results were published in a huge study called DVGW W 55/99 in 2003. The results showed a clear difference The rotational unit MAXINOZ® has two rotation heads with two nozzles each. WTR December 5-7, 2023 ~ Join the WWDR Team in Las Vegas, Nevada, for Groundwater Week - Booth #1326. See more events at www.worldwidedrillingresource.com online issue. Are you planning to go? WorldWide will be looking for you! JET Master Cont’d on page 30.
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