Sand in well

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FiveyRanch

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Hi...first time here. We just had a 340' well drilled to complete in 40' of fine sand. It was a 10" well with a 16/30 gravel pack and a 3" .014 screen to get us 3" of gravel pack thickness. It has a 2 hp pump set at 260' with the top of sand at 280'. We open flowed the well at 18.5 gpm for multiple days trying to clear the sand up. The driller has jetted the well twice. After 48 hour or so of open flow the well clears up of sand but when i shut it off for the night and turn on in the morning it produces a lot of sand that will slowly decrease over 2 days on open flow and then when I shut the well down over night the whole process starts over again with the sand. The driller now wants to cycle it on and off for a week to see if that helps. He is dumbfounded by the way the well is behaving. I have refused to pay him until I get a sand free well. I had a grain size analysis done and the sand when the well was drilled and it ranges from .03 mm to .3 mm. The driller said this size gravel pack would work. Can anyone give me some ideas on what is happening? Thanks
 

Texas Wellman

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You're way ahead of the game. Sometimes, despite all your experience and knowledge, things just don't work out the way you planned (as a driller).

Sounds like he needs to start over from scratch. Once they make sand they will always make sand. He may be able to try something else since he has a 10" casing to work with. Around this part of the state a 4" well would make 80-100 gpm easily. What part of Tx are you in?

I have refused to pay him until I get a sand free well
 

FiveyRanch

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You're way ahead of the game. Sometimes, despite all your experience and knowledge, things just don't work out the way you planned (as a driller).

Sounds like he needs to start over from scratch. Once they make sand they will always make sand. He may be able to try something else since he has a 10" casing to work with. Around this part of the state a 4" well would make 80-100 gpm easily. What part of Tx are you in?
We are over in northern Grimes county. This is the 3rd well in 6 months he drilled. The first was a standard 4" casing well with a 6 gauge screen and a 2 hp that pumped the fwl done to the punp level so right now we have a 1 hp pump in it but only puts out 7 gpm. The second well he drilled the gravel pack failed mainly because we drilled a few hundred feet deeper to see if there was another sand..there was not. So here we are with this one and I believe he is about to bail and give up since he has already lost money on this deal!
 

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Drilling is like gambling. Sometimes it pays off. Sometimes the odds are against you no matter how well you know how to play the game. People wonder why drillers charge so much. He will have to drill about 10 more wells that go perfectly to just break even from what he lost drilling 3 wells for you.

The gravel pack could be bridged off at some point and not covering the screen as it should. The driller could have hit a hard spot that made the well less straight than it should be. This makes the annular space between the casing and wall non existent or at least very thin for a gravel pack.

Put the pump on a timer and let it run for maybe an hour and then be off for some time as well. The raising and lowering of the water level may rinse the sand out and/or help settle the gravel pack.

If all else fails you can use an extra long motor shroud or a Lakos SubK sand separator over the pump.
 

FiveyRanch

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Drilling is like gambling. Sometimes it pays off. Sometimes the odds are against you no matter how well you know how to play the game. People wonder why drillers charge so much. He will have to drill about 10 more wells that go perfectly to just break even from what he lost drilling 3 wells for you.

The gravel pack could be bridged off at some point and not covering the screen as it should. The driller could have hit a hard spot that made the well less straight than it should be. This makes the annular space between the casing and wall non existent or at least very thin for a gravel pack.

Put the pump on a timer and let it run for maybe an hour and then be off for some time as well. The raising and lowering of the water level may rinse the sand out and/or help settle the gravel pack.

If all else fails you can use an extra long motor shroud or a Lakos SubK sand separator over the pump.
He did talk about coming out and putting a timer on the well to let it open flow through the 1 1/4" for an hour or so and then shut off and let it sit and start over. I'll give him a call.
 

FiveyRanch

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I promise the sand isn't doing your new 2hp pump any good.
No is is not. I was a geologist in the oil business for 27 years and dealt with a lot of gravel packed wells and my experience is that once they make sand they always make sand. But I will give my driller the benefit of the doubt one more time. They are coming tomorrow to put a timer on the well so I can run it for 30 min which is the time it takes for the drawdown to stabilize and then turn off for an hour or so and then back on; he said for a week or so. I'll open flow it through the 1 1/4" pipe. The sad thing is I have flowed over 7 years of water use over the past 45 days. I think either they did not get the entire sand covered with gravel or the sand is so fine it is coming through the pack. I question now if he should have use a 20/40 gravel.....but he guaranteed me the well would make 19 gpm (it does) and be sand free (it doesn't)... that is a 50 which was a failing grade when I went to school...ha ha maybe these days it is a C
 

Boycedrilling

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I'm used to dealing with mesh sizes to classify sand, so I can't really correlate your metric sizing of the sand particle sizes.

Your artificial sand pack is either the wrong size or didn't make it to the screen and is passing thru the 14 thousandths slots in your screen. Unless you suck enough sand out to create a big enough void to slow the entrance velocity down or get the sand pack to settle, your going to continue to pump sand. It's bridging up and stabilizing with steady pumping, then becomes unstable when the pump shuts off and the static rises. The process just keeps repeating.

Consider pulling the pump and installing a Lakos sand separator on the pump. It will remove 95% of particles down to 100 mesh. And around 50 % of 200 mesh. I attended a class on the Lakos separator last Saturday. Another way to gauge what they will do is to take a sample of your water. And let it sit. It will remove the particles that take less than 2 minutes to settle out of the water. The Lakos does not solve the underlying problem, but will keep the pump from being ate up by abrasive solids.
 

Boycedrilling

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How much sand accumulates when you fill up a five gallon bucket.

On higher capacity wells, I install a Rossum sand content tester while test pumping. This gives me a measurable sand content, I can quantify the changes in sand content.
 

Reach4

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Does well drilling guarantee results? Is this common? I thought the driller was paid on what he did rather than results.
 

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This varies from place to place. Here where I am we can almost always guarantee water quantity (not quality) due to the numerous aquifers under our feet. Getting the water is no problem. However, there are a few places through the years that we have found are like black holes when it comes to drilling. When we get into those situations we make no guarantees and you pay for each failure. The trick is to know those few areas like that. Most of the time you can still make a good well but you have to deviate from your normal drilling and pay a lot more attention. If we drill a 4" well that makes 10 gpm we consider it a dry hole. I tested one a while back that only made 30 gpm and I was highly disappointed.

Does well drilling guarantee results? Is this common? I thought the driller was paid on what he did rather than results.
 

Valveman

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I thought the driller was paid on what he did rather than results.

He should be! It actually cost a driller more to drill a dry hole than to drill a good producing well. But MANY times the customer will refuse to pay for a dry hole. Only Mother Nature can decide if there is water under your property. All a Driller can do is make a hole deep enough to find out.

I always required that the well was paid for prior to me even pulling equipment on location. You could pay me for the pump system after I get it working. But it is impossible to resale a hole in the ground, so I want that money up front.

I have drilled big wells for farmers before, and after test pumping to find out it makes 300 GPM, the farmer would say, "if it doesn't make 1000 GPM it is not worth messing with". "I am not paying you a dime for such a low producing well, just take your equipment and get off my property".

Those kind of wells are not cheap to drill. After a couple farmers did me this way, I started requiring payment up front. Always being several months behind, if they didn't want to pay up front, I would just go to the next one.
 

Reach4

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Thanks.

Just musing... suppose fiveyranch's driller could stick a 300 ft 1.25 inch pipe down the hole and blow air with a 20 HP compressor. Would that erupt that sand out enough to empty the sand supply for a few years or so?
 

Texas Wellman

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Can 7 maids with 7 brooms sweep the sand off the beach in 7 years?

LOL.

Thanks.

Just musing... suppose fiveyranch's driller could stick a 300 ft 1.25 inch pipe down the hole and blow air with a 20 HP compressor. Would that erupt that sand out enough to empty the sand supply for a few years or so?
 

Craigpump

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There are no 100% guarantees when you're dealing with Mother Nature, except that the sun will come up and go down.
 

Boycedrilling

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I tell my customers that I drill by the foot, not by the gallon. We will find whatever water is there, but we can't create water where there is none.

There are also water producing zone that produce water , but can't be completed into a producing well. It might not be a water quantity problem. It might be a water quality problem. There might be nitrates, arsenic, VOC's, IOC's, or other contamination. It might be the zone has such fine sand or silt that it is impossible to construct a well that doesn't produce sand, silt, or turbidity.

That being said, what works in one area of the country or even world, may not work in another area, or meet local regulations and standards. It's not possible for me to be here in Washington state and say how it should be done in Texas. I just know what works in my area of the world. However there are some things or techniques that are universal.

When it comes to sand there are two things that are critical, velocity of the water, and slot size or particle size of the sand pack. If the velocity of the water is slow enough, it will not carry sand. The slot size of a screen mechanically stops the sand. In a natural sand or gravel pack, the slot size is made to retain approximately 50% of the natural material. This is determined by a sieve analysis of the cuttings. If an artificial sand pack is used, the screen is sized to retain approximately 90% of the artificial pack. The artificial pack is sized to retain the natural sand. I can't remember the exact ratio, I'd have to look it up in "Groundwater and Wells"' the bible of the industry. If I recall correctly the artificial pack should be no more that 4 to 6 times larger in particle size than the naturally occurring sand.
 

LLigetfa

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When it comes to sand there are two things that are critical, velocity of the water, and slot size or particle size of the sand pack. If the velocity of the water is slow enough, it will not carry sand...
The velocity follows the inverse square law so if there is enough variety of particle sizes in the pack, it can stack up from coarse to fine and become reasonably stable. If the granules are all the same size, they won't stack very well to form a lattice.
 

Boycedrilling

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That is correct it is much eisier to develop a sand pack with well graded material, than a uniform or poorly graded material. That is the principal that we use in developing a sand pack well. You are trying to bring the fines into and then out of the well, leaving a coarser sand pack on the outside of the screen. That is why on a natural sand pack we size the screen to retain approximately 50% of the formation material. The finer or smaller grain size material is brought into and then out of the well. Development work may consist of jetting, swabbing, surging, rawhiding, over pumping or other methods to remove the fines from the formation.

In a high production well, it is not uncommon to spend up to 10 hrs of development per lineal foot of screen. Then again some wells require almost no development time. Here again it just depends on the individual well, and the owner's objectives.
 
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