Can You Air Pressure To Clean A Well
Are you using the right amount of air, tools, or time to properly develop the well?
By Mike Toll
There are multiple methods to develop a water well, but the mutual denominator for each of them is energy. Energy must exist produced to develop the well.
Using compressed air is ane such well evolution method. Most of today'due south water well drill rigs come equipped with rotary screw air compressors. Reciprocating piston air compressors have been going by the wayside dating back to the mid-1980s.
"In one case you know these (rotary screw air) compressors, they're pretty simple," says Garth Owens, president of Drill Tech Drilling & Pump Inc. in Chino Valley, Arizona. "It'south not rocket science, but it is a precision unit."
With approximately 15 rotary screw air compressors (2 piston booster compressors) on 6 drill rigs or as auxiliaries on 10 pump hoists, Owens has learned the mechanical intricacies of them. He has rebuilt the compressors, changed their gear sets, and replaced them on rigs while passing forth his knowledge to others in the industry.
"A lot of guys who are drilling don't even have the right air to develop a well and they'll throw a pump down there and but try to pump out the mud," says Garth'southward son, Nick, the managing director at Drill Tech. "It destroys pumps and you're never getting that mud wall cake off the walls behind the gravel pack to really get what the well's producing."
Nick Owens adds that another mutual mistake (come across shaded box for a full list) contractors make comes down to the drilling products used. "A lot of guys drill with likewise much polymer and they never get their polymers out of the wells," he says, "and then sometimes you need things like chlorine to break down the polymers.
"Y'all can drill too large of a well to where the annulus is too large, and you can't go through the gravel pack to get the walls clean. That's a big problem. A lot of guys recall the bigger the hole they go, the more than gravel the better, which isn't necessarily good because you tin can never get enough annular velocity to get through the gravel pack and go that mud cake off. So, you've got to step back and look at the big pic of your annulus to your casing size to your gravel pack.
"A rule of thumb is about 2 inches to 3 inches of gravel pack. If there is more than that, you can't get enough velocity to develop the well."
Sizing Rotary Screw Air Compressors
In that location are drill charts and velocity calculators one can refer to online, but the recommended uphole velocity is about 3000 feet per minute.
"Depending on what size drill piping, what size borehole, what that annular space is betwixt the drill pipage and the borehole determines the corporeality of your cubic feet per minute," Garth Owens explains. "And so your pressure level is determined by how deep you're going to go. Every 2.31 feet of water is one pound of pressure you have to overcome, so basically, it's a 2-to-1 ratio.
"If you lot're going to become 400 feet in the water, you need 200 pounds per square inch (psi). To go 600 feet, you need 300 psi."
To clean the drill cuttings out of the well, the contractor needs:
- Gallons per minute (gpm) and pressure when mud drilling
- Cubic feet per minute (cfm) and force per unit area when air drilling.
Today's standard rotary screw air compressor rating is at least 900 cfm or 1000 cfm/350 psi. Thirty years ago, the standard was 450 cfm/250 psi or 600 cfm/250 psi.
For instance, a 750 cfm/125 psi compressor is half the compressor of a 750 cfm/250 psi compressor considering the contractor is compressing the air twice as tight. Therefore, with a 750 cfm/350 psi compressor, the contractor is compressing the air an additional 50%.
To help visualize it, Garth Owens likens pressurizing the compressor to a scuba tank getting pressurized rather than simply filling a balloon with static pressure.
"Instead of putting 125 pounds in information technology, in social club to put 250 pounds in it, information technology takes a bigger screw and more horsepower to do that," he shares. "And so to go to 350, it takes a bigger compressor and more horsepower to practise that. So, every compressor has two numbers—cfm, and the second number is the corporeality of pressure that information technology puts out at that number.
"For case, for a 750/125 compressor, it'll probably take 125 horsepower to run that. You go to 750/250, information technology'll have you 300 horsepower. You go to 750/350, information technology'll take 400 horsepower to exercise the verbal same matter because you're compressing tighter, tighter, and tighter it takes more horsepower to overcome that pressure level. Then, the higher the pressure, the more horsepower you need."
The water well industry requires compressors rated at extra high force per unit area (XHP), or extra actress high pressure (XXHP).
"Typically, ballpark dominion of thumb, standard compressor is 125 to 150 psi," Garth Owens says. "Loftier pressure is 175 to perchance 200 psi. Extra high force per unit area is normally 350 psi and the highest you'll ever continue a spiral compressor is 500 psi. That'd exist extra extra high pressure to get to 500 psi. Anything after that y'all're running through a piston booster compressor and boosting pressure level with a piston.
"When yous get into the high-pressure compressors, it takes a lot of horsepower, takes a lot of heat, it builds upwards a lot of heat, and information technology burns a lot of fuel, so if the radiators aren't clean, if the fanbelts are slipping, if the radiator is plugged up. . . .Information technology might run great at 250 pounds; yous push it at 350 and 30 minutes afterward the rig is overheated."
To decrease the uphole velocity of 3000 feet per minute, some contractors use drill foam to clean the well at half the amount, 1500 feet per infinitesimal. "If you're using foam and you're filling that void, you're taking half of that void away," Garth Owens says. "You're using half the air because you're filling that void with an bogus substance. It'south going to foam upwardly and blow out and and so it'south going to evaporate and go away."
Well Evolution with Reverse Circulation Drilling
Due to predominately drilling deep large-diameter wells, Drill Tech usually uses the reverse circulation (RC) drilling
method. With RC drilling, the company primarily develops its wells ii different ways.
The company conducts simultaneous swab-and-airlift with its double-swabbed development tool (see right photo) or uses high-velocity horizontal jetting.
The double-swabbed tool has perforations betwixt the two swabs. Airlifting typically occurs through the drill pipe "from which the evolution swabs are suspended, so as the swabbing activity brings suspended solids into the well, they are purged past the simultaneous airlift system," writes Marvin F. Glotfelty, RG, in his volume, The Art of Water Wells.
"The air comes out of the end of the drill pipage, comes upwardly and hits that rubber swab which is the aforementioned diameter as the casing," Garth Owens says, "and therefore all that air has to go out the perforations, blows into the gravel pack, spins that effectually in in that location, and cleans the gravel pack and cleans the borehole. Then the water comes upwards through the gravel pack and comes back to the perforations above your swab and comes out the top of the well."
Glotfelty writes how this well development method is constructive considering "information technology provides both inward and outward energy to break down and remove the wall cake, without forming sand bridges in the next formation."
"We'll actually create a vacuum and pull it between sections there," Nick Owens says. "That'due south why at that place's a rubber swab above and below the holes. Typically, if you want to practise an air swabber, y'all don't need the rubbers because you lot're just blowing information technology out through the perforated screen into the formation."
The company'due south high-velocity horizontal jetting tools allow information technology to adjust the corporeality of air it needs to push through them. "That style information technology's blowing the air through the perforated screen, through the gravel pack, and then we're trying to develop all that mud off there if it's a mud hole," Nick Owens says.
The company has an additional high-velocity jetting brawl tool with approximately 20 holes each drilled to iii/16 inches around it. A loftier-pressure pump is used to pump freshwater down the well at 2000 psi.
"That will non only churn and plow that gravel, simply information technology places that mud thinner all the manner back to the borehole to knock off the wall block," Garth Owens says, "and once you're washed pressure jetting information technology, then you'll come up back and re-swab it and RC it all back out of in that location."
Drill Tech, which had a backlog of approximately 100 wells and 30 pumps to install as of tardily July, stresses it all starts with the design of the well, drilling information technology correctly, using the right products, and not overusing polymers.
"If we're RC drilling, we'll mud upward the top and then nosotros'll case the peak off," Nick Owens says. "There'southward some wells out here where nosotros live where the tiptop 300 feet is all alluvium and there's no water in it. We'll mud those upward, nosotros'll set a 300-pes surface casing, and we'll RC drill the bottom out with only pure h2o considering it's just solid rock. So, nosotros don't utilize any product.
"We can literally drill a 1200-human foot well, pull out, put our casing in it, and gravel pack it. Y'all can trip in every bit soon every bit we're done with zippo development and can video the well, it'south that make clean. Something of that nature doesn't take much development because we didn't put any product in the well. Information technology merely depends on where we are."
To drive home the importance of using the correct amount of production, Nick Owens recalls a large drilling company that installed ii large municipal wells 10 years agone in central Arizona. Information technology both drilled with and pumped besides much polymer into the wells and was unable to get the polymer out. The wells produced 300 gpm.
"We drilled another wells near them, and we got 1200 gallons per minute out of the wells and the aquifer just simply because of the development and not using polymers," he says, "and so [it's] a big thing to brand sure of the product when y'all're drilling and make certain you're using the right product that you lot tin get back out—that'due south the biggest thing."
Important Considerations
Garth Owens has noticed a well development trend that shouldn't be emulated by others in the industry.
"Most guys will just trip their drill piping straight in, blow it direct up the pigsty, and they're done," he shares. "Only you'll get a lot more water out of your well, you'll pump a lot less sand, and y'all'll have a much better product well with a higher pumping level if yous clean that germination out and get equally of that mud that you lot put in back out again. The only way to do that is with pressure through the perforations."
While drilling in July in California, Garth Owens besides noticed large amounts of gravel being put into big diameter wells drilled using the mud rotary method. "They think that the bigger the pigsty is, the more gravel they put in, the better it is, which is not true. What they don't get is the bigger the hole gets, the worse development job yous can exercise.
"Allow's say you drill a 16-inch hole and put in 6-inch casing, and yous've got 5 inches of gravel on either side of you lot, yous cannot become plenty pressure through 5 inches of gravel to make clean the wall cake off the borehole on the outside to become it to produce. The well is however going to produce, but information technology would be a lot amend producing well if it has ii to iii inches of gravel and yous've got enough free energy that y'all can button through that."
Low-cost gravel too has its disadvantages, with it being crushed and therefore athwart. These athwart pieces all wiggle together and lock together similar scrap seal on a highway in the well, according to Garth Owens. This causes a slowdown in the production of water.
"Most people don't employ any chemicals to break downwardly that wall cake considering it costs $250 a bucket," he says, "so we'll get out and drill a well that will make 500 gallons per minute, and our competition literally on the next lot is drilling 100 gallons a minute. And it's simply because of the gravel pack and the development process."
Well development tin can accept multiple hours, so information technology'due south vital to plan and include it in the budget.
"Time is one gene, they want to become to the next task," Garth Owens says. "Another factor is they don't want to put a swab in to pressurize the perforations. The tertiary thing is purchasing the cheapest gravel they can because they think they're going to overcome all that past drilling a pigsty that'southward one or two inches bigger in diameter and now all that other stuff is irrelevant."
In summary, Garth Owens says the idea in amalgam a well to produce is to:
- Determine the drilling germination
- Determine the granular size of the ground that ane is trying to keep out
- Install the largest gravel to have the most square inches of opening and the least friction for the water to come through just finish the finest particles of sand.
"You design with possibly a 10 percent passing of sand," he says, "and then you desire to go down there and develop it until that 10 percentage gets downward to 0.five percentage or 0.25 percent. Y'all want to airlift develop that until you've diddled out everything, y'all've agitated it, washed out the gravel, washed off the wall cake, and so the basis itself and those fines come out of there.
"The coarser material that's in the ground will offset building its own gravel pack on the backside of your gravel pack. If you practice it correct, you can go in and develop a well in four or five hours and have a beautiful well.
"If you don't do information technology right, you can spend three or four days pumping sand because the gravel is as well fibroid. You lot put in too coarse of a filter and the sand just keeps flowing. It takes forever, if it always does terminate. Too fibroid of a sand and it'll never cease."
Maintenance of Rotary Screw Air Compressors
As mentioned earlier, rotary spiral air compressors are simple in nature.
For a high-pressure compressor, in that location are 3 gears in the bellhousing and two low-stage screws and two loftier-phase screws. The simplicity allows the compressor to final for an boilerplate of 10,000 hours.
However, unlike with a reciprocating piston air compressor, Garth Owens cautions against closing the downhole valve, build maximum pressure level, and jerk the valve open with a rotary screw air compressor.
"Because on a piston compressor, yous but take a receiver tank that just holds air," he says, "and yous can pressure it up to 250 to 300 pounds and jerk the valve open and that big surge of air is what blows out silts and rocks when information technology won't practice it when steady drilling.
"On a spiral compressor, when you lot max out the pressure at say 350 pounds, and yous've got the same force per unit area within the filter as you do on the outside of the filter, when you blast that ball valve open up, the pressure differential escapes faster inside than information technology tin can equalize. That's what causes that filter to plummet and blow all your oil downward your hose. That'southward the ane and only thing you don't exercise with a screw compressor—build up to max pressure and jerk the valve open up—that you can do with a piston compressor."
For years, automatic transmission fluid (ATF) was the standard for lubrication on compressors. Today, constructed compressor oil is used because they must run at about 225 degrees to 275 degrees to vaporize the water every bit it sucks moisture out of the air when drilling. "Information technology sucks all that wet into information technology and it rusts up all the bearings and gears," Garth Owens says, "then past turning the thermostat up then hot, information technology vaporizes and burns the condensation out of information technology.
"In that location'due south a water bleed on the compressor that you lot drain every day, and information technology'due south imperative that y'all proceed the temperature upwardly on a screw compressor for condensation reasons."
The flashpoint for synthetic compressor oil is about 400 degrees; ATF is well-nigh 300 degrees.
"You hear most a lot of rigs burning down and compressors burning downwardly, it's typically considering they accept one-time non-synthetic oil because information technology costs less," Garth Owens says. "What happens is the tolerances are very tight in a spiral compressor.
"Typically, there's 3 thousandths max tolerant in a screw compressor, then you really accept to keep your air filters clean, your oil filters clean, and your oil good. When that tolerance starts to become loose, when you showtime getting a bearing wearing out or one of your screws starts wearing into the impeller of the compressor, when that tolerance starts to go loose at all, typically your oil temperatures skyrocket tremendously. Information technology'll run at 200 degrees for 10 years so of a sudden, yous're wondering why it's running at 275 degrees and trying to cook the hoses off your rig."
The commencement indication is typically losing a bearing when the oil temperature begins climbing with the tolerances getting loose. "You either take steel on steel friction, or the tolerance is and so loose that subsequently yous've compressed this air and oil, it scoops up the air and oil and pushes it through the screw," Garth Owens says.
"Because the tolerance is so loose, information technology squirts right back out of it and now you lot've built more friction, more heat, and information technology has to scoop it back up again. So as the spiral compressor starts to leave, the book of air starts dropping and the temperature of your oil starts increasing. Those are your outset indications that when the oil temperature is coming up, you've got screw impairment, and when your cfm of air goes down, you accept damage."
Avert These 10 Mutual Well Development Mistakes with Compressed Air
- Using besides small of an air compressor
- No swabbing or jetting tools
- Too much polymer used when drilled
- Besides large of an annulus, resulting in too much gravel between well and casing, or non enough gravel between well and casing
- Not using mud thinners
- Using the wrong types of gravel that are not well rounded
- Not developing the well long plenty
- Not including fourth dimension to develop the well in the budget
- Non charging the customer enough to develop the well
- Not spending time in each zone but just blowing from lesser to the summit of the well.
Learn More About Well Development
Marvin F. Glotfelty, RG, discusses various types of well evolution (including swab-and-airlift) and concrete attributes of the well that will be impacted by the diverse development methods in an NGWA: Industry Connected video.
Click here to learn more about Glotfelty's book, The Art of Water Wells.
Mike Price is the senior editor of Water Well Journal. In addition to hisWWJ responsibilities, Price contributes to the Clan's scientific publications. He can be reached at mprice@ngwa.org, or at (800) 551-7379, ext. 1541.
Source: https://waterwelljournal.com/well-development-using-compressed-air/
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