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Drilling the Hole

The secret to percussion drilling is to focus on making mud.
All well drillers do is make mud in the hole and lift it to the surface.

Starting the hole

To determine where the exact center of the new hole will be, attach the bit to the rope and have it raised a foot above the earth by the pullers. When it stops swinging, have the pullers let it down to mark the spot where the well will be drilled. To keep the hole straight it must be positioned directly underneath the pulley. When the pulley is pulled by the pullers it will shift towards the pullers. When the pullers lift the bit above the ground the pulley will shift and show where the true center of the hole will be.

While you are drilling you will want to make sure that the pulley and the tripod are secure. If the tripod should move the pulley will move with it and the bit will no longer cut a straight hole.

With the center marked on the ground, start a hole with a shovel or auger or post-hole digger. Try to keep the hole no more than sixteen inches wide and dig as deep as you can. We would even chop up the earth with the bit and then scoop out the dirt with the shovel or our hands. When the hole is six feet or deeper, then switch to the drill. The first ten feet are messy and difficult with the bit and bailer, so do try to dig as deep as you can before you start to drill.

Lower the bit into the hole, pour in a couple of buckets of water, and start drilling!

The driller's job

The driller guides the bit into the hole and works to keep the drill in the center of the hole. If the mud at the bottom of the hole becomes thick, the driller adds water. The driller gives the pullers instructions on how far to raise the bit. The driller also pulls downward on the rope when the pullers let go of it so the rope heading into the well will free up and let the bit fall by its own weight.

When the driller sees that the well has several feet of mud at the bottom or when he can feel that the bit is not striking the bottom of the hole with much force, he tells the pullers to pull the bit from the hole. When the bit surfaces, the driller guides the bit to the side of the hole where it is leaned against the shelf.

The driller then takes the rope off of the bit and attaches it to the bailer. This should be done quickly so that the soils in the mud at the bottom of the hole do not have a chance to settle. Giving a signal to the pullers, the bailer is raised and then lowered into the hole.

When the bailer hits the mud its flap should open and the bailer should fill. The driller can see and feel if the bailer is filled with mud. If the flap is stuck, or if there is not much mud in the bailer, or if the soils settled, the driller instructs the pullers to lift and drop the bailer several times. This will stir up the mud at the bottom of the hole and fill the bailer.

The driller gives the signal to the pullers and the bailer is lifted out of the hole. The driller guides the bailer to the side of the hole where the mud will be dumped and then signals to the pullers to lower the bailer to the ground. The driller then pushes the top of the bailer over the log or stone so that the bottom of the bailer is resting on the log and the top of the bailer is resting on the ground. The mud should pour out, but if some of it sticks inside the bailer the driller will need to knock the bailer until the mud loosens.

When the bailer is empty, the driller signals the pullers and they lift the bailer. The driller guides the bailer over the hole and then signals the pullers to lower the bailer into the hole again.

This practice is repeated until the driller sees that the hole has been cleared of as much mud as possible. The driller then guides the bailer over to the shelf and re-attaches the bit.

One of the most common mistakes made by new drillers is to allow the bit or bailer to be dropped from the surface to the bottom of the hole.  When this is allowed to happen, the bit sticks into the mud at the bottom of the hole like a spear and is very difficult to loosen.  The tools should always be lowered slowly and carefully.

The puller’s job

The puller mostly just pulls the rope. When the rope is tied to an anchor the puller pushes the rope down to make the bit raise a foot or two and then lifts the rope back to its resting position quickly so that the bit can drop by it own weight to the bottom of the hole.

The puller pays close attention to the driller and the signals that the driller sends.

When it is time to bail the hole, the puller will lower the bailer into the hole and then, after lifting and dropping the bailer a few times to fill the bailer, grab the rope and run with it until the bailer reaches the top of the well hole. One way to make sure that the puller does not run too far and make the bailer run into the pulley is to mark a spot on the ground at the point that the bailer is clear of the hole. The puller can then run to this spot and stop.

Of course, there are usually six or more pullers on the rope. To have twelve pullers would be ideal, but to have more may be difficult to organize. If you have more pullers, you may want to organize teams that can take turns so that the pullers do not tire.

The first ten feet

The first ten feet of the well are more difficult to drill because the bit can move around more inside the hole and the splashing inside the hole can make a mess of the driller.

The driller has to work much harder to keep the drill bit centered in the hole during the first ten feet. There is no good advice we can give you. It just takes patience and practice. Lift and drop the bit only a foot and keep plenty of water inside the hole.

The hole will be wider at the top and then will narrow as you drill deeper. As it grows more narrow the bit will not move around as much and the drilling will become easier.

Keeping a well log

As you drill through the earth you will want to keep a record of the depths and types of soil and rock you find. This record is called a well log and is important for two reasons. First, if you note which types of earth you find water in, you will know what to look for when you are drilling other wells. Secondly, the record will help you to know how fast you are drilling and will help you to learn how to change your drilling style to best drill the different types of earth.

In Chapter 5 we discussed two tools which will help you keep a well log. The tape measure and the depth gauge. The depth gauge is a long string with a heavy weight on the end. Lower the heavy weight into the hole until the weight hits the bottom of the hole. Mark the string at the top of the hole and then remove the depth gauge from the well hole. Lay the depth gauge out on the ground. Using the tape, measure the distance from the end of the weight to the mark on the string. This shows how deep you have drilled.

By measuring the well hole often, you can see how fast and how deep you are drilling. Keep a written record of each measurement. Then, by subtracting the last measurement from the current measurement, you can find out how much you have drilled since the last measurement was taken.

For example, imagine that you bailed the mud out of the hole and then measured it to find that it was 120 inches deep. After drilling for a half hour you bail the hole again and then measure it. This time the depth of the hole was 136 inches.

136 inches Current depth of hole
- 120 inches Previous depth
= 16 inches Amount drilled in between

This means that you drilled sixteen inches in a half hour. This is very good progress!

But if everything comes out of the hole looking like mud, how do you tell what it is that you are drilling through at the bottom of the hole?

In Chapter 3 we discussed the sand screen. This is a tool made from wire mesh or mosquito netting stretched over a frame. Another option is a strainer with a fine mesh that is sometimes used in cooking.

Pour some of the mud that has been bailed out of the hole into the screen and wash it with water. Having a bucket of water on hand for this purpose is a good idea. The washing will clean the dirt away from the sand, stones, and rock chips. You can then look at what is left in the screen.

Are there small stones in the screen? Do they look like they are breaking? Are there rock chips? Wash them carefully and compare them to other rock chips you have found in the area. Do you recognize the type of rock? Is there a lot of sand in the screen? Is the sand course or did the fine sand wash out of the screen? Are there pieces of clay in the screen? What color is the clay? What color was the mud?

Make a note in your well log of the types of earth you are finding. Compare the types of the earth with how fast you are drilling. Is the type of earth easy to drill? Did it take a long time to drill the last few inches?

Practice and good note-keeping will help you to learn the well drilling craft. With time you will become an expert in the types of earth in your area and your well drilling will become easier. If you have kept good notes, you will know what you will be drilling through if you make a second well in the area.

One more very important reason for keeping good notes on the progress you are making is to avoid cave-ins.

Cave-ins happen when drilling through loose earth, like sand, that can fall away from the sides of the well hole and fill up the bottom of the hole. Cave-ins can trap the tools at the bottom of the hole and you may not be able to get the tools out again. If you have good notes, you will be able to judge if you will run into cave-ins.

Imagine you have been drilling for an hour and have been bailing mud with a lot of sand out of the well hole. When you measure the hole you find that you have made no progress. You look at the pile of mud that you have brought out of the hole and wonder what has happened. It may be that the sides of the hole are caving-in and that the hole at the bottom is only getting wider, not deeper. You will want to test by drilling some more and measuring again, but it may be that you will need to use casing. We discuss casing later in this chapter.

Drilling different types of earth

The most common type of earth is slightly moist dirt with a little clay, a few rocks, and sand mixed in. Drilling through this type of earth is easiest. The instructions given so far describe drilling through this type of earth. But the drilling technique changes slightly for other types of earth.

When you are drilling through earth that has fine dirt and clays, the mud at the bottom of the hole may become too thick. When this happens the bit can sink in easily and be very difficult to pull out. Pour in extra water to loosen the mud. Keep the mud from becoming too deep by bailing the hole out more often.

Drilling mud, as well as drilling sand or other loose formations, may be easier if you use only the bailer. A tapered edge on the bailer is handy at this point. Lower the bailer into the hole and raise and drop it as you would the bit. (Don’t forget to add water!) If the earth at the bottom of the hole is loose enough, the bailer will fill by itself without using the bit.

Drilling rock can be tedious. Sometimes you may only drill a foot or two in one day. But drilling rock is still much faster and easier than digging rock! The rock you are drilling may be a boulder that is only a few feet thick (look around the village or town around the well site to see what kind of boulders are in the area) or the rock may be a layer a hundred feet thick. Look at the cuttings coming from the hole. Do they match rocks found on the surface?

If you suspect that the rock you are drilling is part of a large layer (if there are nearby outcroppings or cliffs made of the same rock) it may still be worth drilling. Some very good aquifers are found in the cracks of rocks. Other good aquifers may be found under the rock. In some areas you may have no choice: sometimes the only aquifers are found under the rock layers.

Your own experience, as well as the experience of others who have dug or drilled wells in your area, will be your guide. If you are not sure, try to drill for at least a full day. If you can drill five to ten feet a day, you are making excellent progress and it may be worth continuing. If you find that you are not getting very far you may want to move. If the area your are drilling in has boulders, you may be able to move your drill a few feet in any direction and drill right past the buried boulder.

Finally, since drilling through rock is slow, you will find that you do not need to bail as often. There are some different drilling designs in the last chapter of this book. One of them, like the Spring Pole or inner-tube method, may work better and use less labor when drilling rock.

Try experimenting with all the designs to find out which ones works best on the types of earth in your country. As you gain more experience, you will come to know which methods work best in different situations.

Making mud

The secret to percussion drilling is to focus on making mud.

All well drillers do is make mud in the hole and lift it to the surface.

The best kind of mud is thick enough to keep the drill cuttings suspended in the hole so that the bit can cut away at the bottom without interference.  The thick mud also keeps the drill cuttings suspended long enough for the driller to extract the the drill and drop in the bailer.

If there's too much clay in the hole, the mud will get too thick and your bit will move too slowly to cut the bottom of the hole.  So you add water to make a thinner mud.

When you are drilling in rock or sand you may find that the mud at the bottom of the hole thins out and is mostly water.  The job of the mud in the hole is to suspend the chips of rock and soil so that they can not sink too quickly to the bottom of the hole.  When the mud becomes too thin and runny, the chips of rock can sink to the bottom of the hole and cushion the impact of the bit on the rock.  The remedy is to pour mud into the hole to thicken the water.

The best kind of mud is made from fine clays with no rocks or organic matter found in dry puddles or river beds.  If need be, sort the mud through a screen or sieve first to make sure that there are no rock chips in it.  Mix the clay with water at the surface to make a thick mud slurry and pour it into the hole.  One idea is to dig a small pit and using stomping feet to mix the clay.

When working in sandy soils, use the bailer to agitate the cuttings (lifting and dropping it 5-10 times) before trying to remove the cuttings.

When drilling through lots of sandy or gravelly soil, you can conserve your mud by making a settling pit for the mud extracted from the hole.  Dig a shallow pit near the well and line it with thick clay, or, if possible, plastic.   Pour the mud extracted form the well into this pit and let it sit so that the rocks settle to the bottom of the pit.  Then you can skim off the mud at the top and re-use it in the well.  (After the pit has settled overnight, set someone to sorting out the cuttings from the mud so you can reuse the mud as much as possible.)

It will take practice to learn which thickness of mud works best, but remember: The secret to percussion drilling is to focus on making mud.

Putting things on hold

When it is time to stop drilling at the end of the day, or if you are taking a break to eat or rest, it is important to remove the tools from the well hole.

Two things can happen to tools that are left inside the well hole. First, when the hole dries there might be a cave-in that would trap the tool at the bottom of the hole. Second, the mud at the bottom of the hole can dry up to be as hard as cement and trap the tool. Either way, you may not be able to remove you tools if they get stuck.

It is a good practice to clean the tools and the rope at the end of each day. The rope will last much longer if all the mud is cleaned off and it is hung to dry out. The other tools will also last longer and will be easier to use the next day if they are not covered with dry mud.

What to do in emergencies

If a tool does become stuck at the bottom of the hole, or if the tool falls off the rope, some special measures will have to taken.

In any case, it is very important to work as quickly as possible because of the dangers of cave-in or the mud drying.

In Chapter 3 we discussed the fishing tools. The fishing tools are hooks that can be used to catch the loop at the top of the drill bit or bailer.

If a tool has fallen off the rope, attach the fishing tool to the rope and lower it into the hole. If the hole is shallow, you can use sticks to help guide the fishing tool into the loop, but if the hole is deep you will have to use your sense of touch to feel when the fishing tool is in or around the tool. It is also very helpful to have others around the hole be very quiet so you can hear the sounds of the tools when they meet.

If you do not hear the tools touch and think that the tool may have become buried in a cave-in, measure the hole to see how much of the hole has been filled in by the cave-in. You may be able to push your fishing tool into the loose earth at the bottom of the hole by attaching it to a heavier tool like the bit or a pole. Use this option last because it can also push your tool deeper into the earth and make things worse.

If your tool is stuck at the bottom of the hole you will want to work fast. The best way to provide extra pull on the tool is to use leverage. Place a log or stone next to the well hole and lay a heavy pole across it as a lever. Tie the rope around the lever as the short end is in its lowest position. Push the lever down at the other end. Watch the rope closely. If the rope looks like it is straining too much and might break, stop pushing.

When the rope looks like it might break from the strain, it is time to double the rope. Attach another fishing tool to the loose end of the rope and hook onto the tool’s loop. Tie both ropes to the lever and try pulling the tool out again.

Pour a lot of water down the hole to loosen the soils and push and pull the rope from one side of the hole to the other to make the stuck tool shift.

We have spent many hours working to loosen bits we were sure were lost forever, only to have someone come up with an inspiration that slipped the bit out. Sometimes it just takes lots of patience. Good Luck!

Using casing

Casing is needed in soils that cave-in easily. Casing is a steel pipe that holds the hole open while it is being drilled deeper.

In many soils casing is not needed at all, and it saves the driller time and expense to drill without casing. In other situations, the added risk of drilling without casing may not be enough to cause the driller to use casing. But in some loose soils, and you can find out from other drillers in your area if you might find such soils, casing is necessary.

The inside of the casing is wider than the bit and the bailer, so the tools can be used inside the casing. For example, if your bailer is six inches wide at its widest point, then the casing would need to have at least 6 1/4 inches room on the inside.

Casing comes in pieces from six to ten feet long that are joined as the hole gets deeper. Some casing can be welded together and cut when removed, but this might be too complicated for some situations. Other casing has threaded ends and screws together using a coupler. This type is usually preferred, although the threads can be difficult to repair if they are damaged in the field.

Many times casing simply sinks in the hole by its own weight, and sometimes it must be slowed down. Sometimes it needs to be pounded into the well hole. In both cases we use casing clamps, tools that grip the casing without damaging it.

Simple casing clamps can be made by using wooden planks or poles that have been cut to fit the round shape of the casing. Better casing clamps can be made with bent steel. The clamps are bolted or tied together so that they squeeze the casing between them. By pushing or lifting on the casing clamps, the casing can be moved in and out of the hole.

The bottom of the casing, like the bottom of the bailer, has a rim of hardened steel called a "shoe". The shoe cuts away at the side of the hole and protects the end of the casing from becoming bent.

While you are drilling you will want to work as much as you can without a casing.

When the casing is needed, attach the boot to the bottom edge of the casing and the coupler to the top. Attach the clamps to the casing just beneath the coupler so that the casing cannot slip out of the clamps.

Stand the casing upright and move it into the hole. If the casing stops sinking, place weight on the clamps and pound until the casing sinks and the clamps are at the top of the hole. Do not pound on the top of the casing unless you have inserted a piece of wood or a metal sleeve to protect the threads.

Screw a coupler on a second piece of casing and attach it to the first piece. Holding the casing extra tight, move the clamps over the first coupler so that it grips the second piece of casing below the second coupler.

Keep attaching casing until the hole is lined. But be careful not to leave too much casing sticking above the ground because it will be hard to move the bit and bailer in and out of the hole. With a good measurement of the hole you will be able to know how much casing is needed.

The drilling continues the same way with the casing installed. If the bailer gets stuck in the casing when a rock gets between the casing wall and the bailer, lower the bit on the other end of the rope and lightly tap the stuck bailer to dislodge it.

Later, when you have finished drilling and installed the permanent casing, you will remove the steel casing. The casing might pull out with the rope, but it will usually need a little extra lift, like with a lever or car jack.  Attaching casing claps and turning the casing will make it easier to remove.

Attach the rope to the casing clamps and pull. If the casing seems loose but will not come out, tap the side of the casing and move it back and forth at the top of the hole. If pulling does not work then lifting might. Using the same leverage design mentioned in the section on emergencies, put a lever under each side of the casing clamp and lift. Another trick is to use a car jack under each side of the clamp.

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Wellspring Africa's
Hand Powered Percussion Drill

Copyright @ 1986-2012
by Cliff Missen and Wellspring Africa