Water Well Drilling Rotary or Pounder

[WadeMccann]

I've had good results with rotary drilling, especially in sandy soils where a pounder might struggle. A big factor is the depth you need and the type of formations you're going through. One thing I’ve learned is that experience matters as much as the method. Island Well Service knows how to handle different ground conditions, and they can help figure out what works best for your location.

 

[etpm]

When I had my well put in way back in '96 or '97 I researched wells, how they are drilled, how they develop, etc. I called the state for advice and spoke with many people who had wells put in. In the end I had my well done with a cable tool. In my area the price per foot was the same, rotary or cable tool. I chose the cable tool for several reasons. But the two major reasons were that a cable tool usually gives you more water because it fractures the rock as it goes through and doesn't use drilling mud. The rotary rigs either use high pressure air or mud and both methods tend to clog the pores in the rock. Also, I was warned by not only the state but by several folks that had rotary rigs drill their wells that the rotary rigs drill so fast that they can shoot right through a water bearing layer and drill deeper to another water bearing layer. And you pay by the foot. The cable tools go slower and when they hit water they don't blast through it. I tried drilling my own well with one of those Hydra Drill rigs. Everything went great for the first ten feet or so. Then I hit hardpan which was almost as hard as sandstone and the damn thing just wouldn't drill. I was only getting about an inch an hour. So I got the well done with a cable tool. They went through 40 feet of hardpan before they hit the aquifer. It took them 5 days to get through it. I'm glad I was paying by the foot. I get 15 gallons per minute or more. so I'm happy.
Eric

 

[caver]

Cable tool drillers are still out there but can't say I know of any in MO or AR.

 

[etpm]

Cable tool drillers are still out there but can't say I know of any in MO or AR.

I don't know the difference between a pounded well and a cable tool. They seem to be used interchangeably but I think they may be different. When I looked into getting my well done there were only several rotary well drillers and one cable tool well guy. The cable tool would drop from high and fracture the ground. It would then retract and in doing so would grab the fractured material and bring it to the surface. I have heard of "drill points" which are just a point of some sort affixed to the end of a pipe which is driven into the ground until you hit water. I have only seen these used for shallow wells in soft ground. But I am no kind of an expert. I can only tell you about what I did when I had my well done.
Eric

 

[Sportsman762]

I don't know the difference between a pounded well and a cable tool. They seem to be used interchangeably but I think they may be different.

They are the same, also called driving a well.

But the two major reasons were that a cable tool usually gives you more water because it fractures the rock as it goes through and doesn't use drilling mud. The rotary rigs either use high pressure air or mud and both methods tend to clog the pores in the rock. Also, I was warned by not only the state but by several folks that had rotary rigs drill their wells that the rotary rigs drill so fast that they can shoot right through a water bearing layer and drill deeper to another water bearing layer.

This is my understanding as well. I worked for a drill for a few years, we used a rotary, but towards the end we setup a cable rig to use in some cases. Another advantage of a cable rig is that it has a small footprint so you can wiggle one into areas that you can't get to with a traditional rotary as they are big.

There are downsides to a cable as well. If there is a softer formation on top of a harder formation and the delineation is at a steep angle it will push the bit sideways until the bit can penetrate the hard formation. This creates a dogleg making it difficult/impossible to put the casing in and if left an open bore (no casing) it creates a hazard that can catch a pump / drop pipe causing them to get stuck in the well. Cable rigs suck in hard rock. Your always having to sharpen the bit and it is difficult to trip in and out as you have to screw several lengths of rod to the bit to give it enough weight to break the rock.

There are three major types of drill bits used on rotary rigs. The first two bits use drilling mud to provide lubrication, remove cuttings, and keep the bore open. In normal circulation mud is pumped down the drill stem and circulated up the annular between the stem and the bore wall. Cuttings then fall out in the mud pit before the drill mud is recirculated.
Drag bits are used in soft non consolidated soils such as gravel, and sand. These bits have a fast cutting action and are relatively inexpensive.

Replaceable Blade Bits - BlueDemon

www.bluedemon.com

For more consolidated formations such as sand rock, fractured rock and mixed formation a tricone bit is used. They are more complex than a drag bit and therefor cost more to run.

Roller cone bit - Wikipedia

en.wikipedia.org

The third drill bit is a Down The Hole Hammer (DTH). They are air powered and the air exhaust pushes the cuttings out of the hole. It is like a jack hammer that is being spun slowly by the drill rig. Water is used to help cool the bit but because the formation is hard enough to require a DTH it does not require drill mud to apply hydraulic pressure to the bore wall to keep the hole open. This is the most expensive way to drill a well as the bits and hammers are major money.

DTH Hammers | Center Rock's Down the Hole Hammer

Center Rock offers the most complete line of dth hammers, drills, and bits which are designed for peak performance in all rock drilling applications.

centerrock.com

Hope this helps.

 

[caver]

I've heard some call them pounders, some call them cable tool or percussion rigs.

I grew up in a subdivision just outside the city limits. We had city sewer but everyone was on wells. As it expanded you could hear the cable tool/pounder rig echoing throughout the neighborhood.

 

[Sportsman762]

I've heard some call them pounders, some call them cable tool or percussion rigs.

I grew up in a subdivision just outside the city limits. We had city sewer but everyone was on wells. As it expanded you could hear the cable tool/pounder rig echoing throughout the neighborhood.

They also call them churn drills, spudders, and donkey rigs, there is probably a dozen names for them.

Was working in a fancy area and decided to set the casing (put casing in the well) on Thanksgiving morning. It should have been a quick couple of hours, but the bore had partially collapsed. We ended up pounding the casing in with the hoist line and a 800lb drive block. Took us all day, I am sure the neighborhood appreciated the incessant pounding until 9:00 that night when we finally got the casing in. Its hard to find days that are not frozen in November in Minnesota, sometimes you have to do what needs done.

 

[mapper]

If your area has a lot of loose sand or gravel, rotary might handle it better. Pounders are great for rock, but they take longer. Depth and soil type matter a lot.

Around my neighborhood the soils are deep glacial till with layers of impermeable hardpan. Lots of huge boulders are buried in it. There are several water bearing layers in it, some good, some not so good. Most of the wells are at a depth 60-100'. Some pounded, many rotary.
When our next door neighbors well was drilled they started with a hammer rig. The spud got jammed between boulders about 30' down. The driller finally ended up snapping the cable while trying to pull it loose. They had to bring in a rotary rig and drill a new hole. From what I saw of the cuttings bed rock is way below the wells around here.

 

[etpm]

From what I saw of the cuttings bed rock is way below the wells around here.

Here on the south end of Whidbey Island the glacial till formation is 3000 feet thick. So the bedrock is way down below. And you never know when you will hit water because of the mixed up nature of the glacial till. You also never know what kind of stuff will be in the water. It may be stinky from sulfur, it may be hard, it may have arsenic in it, etc. All of the wells around me are more than twice as deep as mine, some only produce about 6 gpm, some are stinky.
Eric