When it comes to drilling, the overburden is usually the easiest layer to deal with. It's when drills finally hit hard rock formations that progress can dramatically slow down.

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If you're running into this problem, it might be time to invest in heavier, more rugged drill rigs and accessories to power through the dense material. A down-the-hole (DTH) hammer is a great example. It can drill as deep as 300 feet through limestone, sandstone and quartzite faster than standard mud rotary bits.

The DTH hammers Lone Star Drills offers operate with a wide range of drilling equipment without the need for specialized adapters. Our 3-, 5-, and 6-inch-diameter hammers can be powered with air compressors with outputs as low as 185 cfm. This means you can use them with construction compressors that are readily found on the used equipment market or through rental dealers. To achieve faster drill speeds, use a more powerful air compressor.

The 3-inch model can be used with a 4-inch internal diameter casing set in the overburden to drill a 3-3/4-inch or 3-7/8- inch borehole in underlying rock. You can use the 5-inch hammer with 3-1/2-inch drill pipe to drive a 5-7/8-inch borehole through hard rock formations.

Drilling effectiveness also depends on factors such as anchoring requirements, bit types and the drilling unit itself. For heavier, trailer-mounted rigs, anchoring isn’t always necessary. But for smaller, lightweight drilling equipment, such as the LS200H, LS200H+, LS300 and LS300H+, anchoring stabilizes the drilling platform and helps force drill bits through soil and rock.

Lone Star Drill’s LS200H and LS300H series drills require 30-inch-long anchors for drilling projects in clay, loamy and sandy soils. But if the drill site is on rocky terrain, drillers have to find a different way to anchor the drills, such as adding water-filled tanks or barrels packed with rocks onto the unit. This anchoring force is crucial to pushing DTH hammers and heavy-duty drill bits through rocky material.

Choosing the right bit not only makes the drill more effective; it also improves the lifespan of the bit and reduces the number of times you'll need to buy replacements. For instance, a drag bit won’t penetrate through the rocky soils and will prematurely wear out. Instead, once the drag bit reaches hard rock, switch to a tricone bit or a DTH hammer to power through.

Importance of Maintenance and Support

Regular maintenance of your drilling equipment can make a significant difference in its performance. Timely checks and updates not only ensure the longevity of the equipment but also enhance safety on-site. Make sure your drill bits are sharp and replace worn-out parts promptly.

Moreover, having access to expert support and advice can be a game changer. At KSQ Technology, we provide comprehensive support to help you select the right equipment for your specific drilling conditions and offer maintenance tips to keep your operations running smoothly.

Finally, picking the right drill for the job can determine how effective it will be, and we're ready to help you choose the ideal rig for your next mission. Check out the full line of Lone Star Hydraulic Drills and contact us today.

Casing Advancement Systems for Down-the-Hole Hammers

Ring bit systems are commonly used for drilling in overburden like boulders or loose formations.

By Mike Price

Water well contractors who struggle with drilling in overburden are adding down-the-hole (DTH) casing advancement systems to their toolbox.

Industry manufacturers have created various kinds of ring bit systems and underreamers over the years that continue to be upgraded for the water well market. While many factors should be considered when choosing the appropriate system, the types of formations contractors are drilling in will largely dictate the decision.

"There are a lot of things to consider, and if the wrong type of system is selected, there can be a lot of problems for both the driller and the distributor that sold the system," says Justin Lewis, product manager of casing advancement and DTH at Mitsubishi Materials USA in Mooresville, North Carolina.

"Choosing which type of device and then using it correctly is much more complicated than standard DTH or air rotary drilling, and in addition to the casing advancement device itself, drillers will also need to either manufacture or purchase additional tools like special lifting slings and diverters to make everything work."

Lewis, who was interviewed by Water Well Journal about DTH casing advancement systems in the August issue, has a general checklist (see shaded box) that he covers with contractors who are considering which system fits best for them. Naturally, which system to choose is one of the most asked questions Lewis gets from those who are just starting out.

"I would say it is close to a 50-50 split on the two kinds [contractors choose]," Lewis says between a ring bit system or underreamer. "Each individual driller is also going to have their reason as to why they use this particular method. The most shared reason would be the ability to get casing into the ground in unstable formations that prevent the hole from staying open."

As Lewis explains, ring bit systems (Figure 1) have two main pieces: a pilot bit that is attached to the hammer and a ring bit assembly that is welded to the bottom of the casing. The pilot bit gets locked into the ring bit assembly to drill the hole and advance casing. The pilot bit breaks the rock, and the ring bit breaks and reams whatever the pilot didn’t get.

In water well drilling, 90% of the time the ring bit assembly stays in the hole. The pilot bit is used on many wells until it is worn out (usually a couple thousand feet), but each ring bit assembly is sacrificial.

Unlike ring bit systems where the drilling gauge is on the ring bit assembly, underreamers (Figure 2) will typically have some type of retractable bit wing or bit head that will extend to start the drilling process. Underreamers are generally used in softer formations containing sands and gravels. They can also be used in harder formations, but the leading edge of the wings/heads will wear out faster and can cause increased rotational torque.

Both the ring bit and underreamers are engaged when turned to the right. To retract the underreamer wings or unlock from the ring bit, turning a half rotation to the left is needed.

Like the dual rotary drilling method, casing advancement systems offer similar advantages while simultaneously drilling and casing holes.

"Even with more and more drillers converting to dual rotary and some even going the route of sonic drilling, there will always be a need for casing advancement systems to drill into the formations that the other rigs can’t," Lewis shares in the August WWJ Q&A.

Selecting Correct Size Ring Bit System

Part of Lewis’ initial discussion with a contractor in picking out the correct size ring bit system is ensuring that the inside diameter of the ring bit is large enough to get the correct size bit to drill through it so they can install a well screen.

The only thing the ring bit assembly regulates is the outside diameter (OD) of the screen. Since the screen needs to pass through the ring bit, care should be taken in the design process to ensure a large enough bit can pass through the ring bit to set the desired screen size.

The casing string that has the ring bit on it will act as the surface casing. The final well completion, casing, and screen that the pump is set in goes through the surface casing.

Example: A contractor needs to drill a well to a total depth (TD) of 360 feet and set 4½-inch OD polyvinyl chloride (PVC) casing and screen to get a 4-inch pump in. The first 50 feet of that hole is through a formation that contains boulders and gravel and won’t stay open to get the PVC in. At 55 feet the formation changes to solid rock. The contractor could use a ring bit system to drill and set 7-inch OD casing to a depth of 60 feet, sealing off the boulder and gravel formation and accessing the solid rock.

The contractor then trips out the pilot bit and trips in with a 6-inch DTH bit and starts drilling through the middle of the ring bit assembly to a TD of 360 feet into the water-bearing formation. The contractor would then trip in their 4½-inch OD PVC casing and screen to complete the well.

The well would then have 60 feet of 7-inch OD steel casing with 360 feet of PVC inside of it. The well screen is secured depending on the well construction requirements. Figure 3 visualizes this concept.

First-Time Advice Running a Ring Bit System

Craig Williams, owner/operator of Williams Well Drilling LLC in Milford, Pennsylvania, has had just one failure in 20 years of running a ring bit system. The failure came during his first job where he “pushed it too far.” This led to clay swelling around the casing and caused the casing shoe to break off.

“I tell everybody: Take your time; don’t be in a hurry because when you try to push a casing system, you try to make it hurry, that’s when it’s going to bite you. Just take your time,” says the third-generation contractor who uses a ring bit system for about 30% of his drilling while the majority is conventional air with a DTH hammer.

The top issue that Williams sees is contractors trying to go fast with casing advancement systems. His two recommendations:

• Don’t run over 150 pounds per square inch (PSI).
• Don’t run a quality hammer.

“There are so many things that aggression is going to get you into problems,” he shares. “That weld is only going to take so much beating and the older hammers clean the hole better. They clean that stuff away from the bit better because they’re bypassing so much air because they’re wore out. Run a wore out hammer because it’ll bypass more air and then it’ll clean that ring bit out better. It’ll keep everything cleaner, and it won’t bind everything up.

“That shoe is only welded on the pipe. That weld is only going to take so much abuse. The hammer that I run my 7-inch system with is 30 some years old, so I don’t worry about hitting the shoe too hard with it because I’m only drilling dirt.

“It’s not like I’m drilling rock all the time. I don’t run over 150 PSI ever—unless I’m in rock. The most I run it at is RPM. I don’t even rev it up. I only got 750 air. I just let it do its thing. Put it in and hold back. I don’t force it and have had very good luck that way.”

If running a ring bit system for the first time, Williams naturally advises contractors not to use it on the hardest job. He says instead to run it on a familiar job.

“If you know you can blow it in with a hammer, but it’s just a little bit tough, that would be the job I do first to get used to it,” he says while emphasizing the need to learn the system.

Welding Skills Needed

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For a contractor to run a casing advancement system, Williams says they need to possess decent welding skills.

“Run good welding rods and make sure your welds are good because you got to remember you’re pulling that casing down, and one bad weld, it’ll find it,” he says.

Williams welds everything with a 5/32-inch rod and burns it as hot as possible. He generally welds with only one pass.

“I’ve never had a problem with one pass breaking,” he says. “My theory there on more than one pass is you tend to overheat the joint and the pipe gets too hot, and it gets brittle. That’s my opinion and not sure if it’s right. I’ve had very good luck running one pass with a 5/32 rod and as hot as the steel can stand it.”

Williams also suggests:

• Ensure the weld is clean. Williams typically rinses it off with a pressure nozzle on the rig before he welds.
• Ensure the casing is straight and the joint is tight together. Williams uses a casing alignment clamp to achieve this. His drilling assistant clamps the casing and looks around it for any gaps. If there is a gap, Williams moves the jacks on the drilling rig to close the gap.
• If the system has them, when filling in the plug welds, start welding in the bottom and work your way in a circle. The plug welds spread the shock out on the casing so it’s not all concentrated to one spot.

Checklist of General Questions to Consider When Deciding Which System to Run

1. Have you used a casing system before?
   a. If so, which type and what did you like or dislike about it?
2. Which types of formations are you encountering when you need a casing system: sands and gravels, boulder fields, rock shelves, etc.?
3. How deep are you planning to drill with the system?
4. Will the casing be removed after the system is used?
5. Do you need to drill through the bottom of the casing?
   a. What size hole do you need to drill through the bottom?
6. Which type of wells are you using the system on: water well, environmental, geotech, construction, etc.?
7. Which type of rig do you have?
8. What air package do you have?
9. What is the casing OD and wall thickness you will use the system on?
10. Which hammer shank are you running?

Below are some of the general questions Lewis asks drillers when deciding which type of system to run. Based on the answers to these questions, either Lewis or the driller may have more questions until everyone agrees as to which type would be best.

Benefits of a Ring Bit System

Williams often contends with wet overburden with flowing sands and clay formations where he’s located in the northeast corner of Pennsylvania. The casing advancement system has been a game-changer for him.

“Jobs when I first started business it’d be two or three days just trying to get pipe in. Now I go put pipe in two or three hours with a casing system,” states Williams who opened his business in , “and it’s done and just makes my life that much easier.

“It’s more setup and getting going; it takes about an hour to set up and get going, but once we’re going, we’re putting 20 feet an hour in. And the thing is, once you drill those 20 feet with a casing system, that’s 20 feet that’s done. You don’t have to mess with that again.”

Like with the dual rotary drilling method, Williams benefits from seeing instant samples of what he’s drilling in. There are no mixed samples.

“I know exactly what I’m in immediately,” he shares. “That’s really nice. Color changes and whatever.”

Knowing his formations before drilling is essential, and if Williams knows it’ll be 400 feet of casing, he won’t use his casing advancement system. He’ll use the mud rotary drilling method. But if he knows it’s 160 feet to rock but challenging drilling, he’ll use the casing advancement system.

“Ninety percent of my drilling is less than 200 feet of pipe,” he says, “so I get a lot of jobs where I only put in 80 feet of pipe, but it’s nothing but sand and gravel all the way down. Our issue here in this area is we have a very hard top layer on the rock, and you drill 5 feet into it and the rock is loaded with water. The quality of that water is garbage, so you want to seal that water off and get 15 or 20 feet into the rock and seal that top water off.”

Williams, whose wells are 95% open hole in bedrock, also loves the versatility of a casing advancement system in an area that has numerous gravel wells. He can run the system down and stop the bottom of his casing wherever he wants.

“If you’re drilling and driving in gravelly or sandy formations, you drive the pipe down, then you’d have to cut it, trip in the hole, clean it out, blow on it, see if it’ll clear. If it won’t clear, weld on another piece of pipe on,” he explains.

“For a casing system, I can drill it down to a gravel layer and unhook from the drive shoe and pull up inside the pipe and blow on