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Section 3

How to Drill with the LS-100 line

Experience in developing countries has shown that the construction of drilled wells must be simple and efficient. This keeps projects affordable, maintains a certain momentum and enhances local enthusiasm. Section 3 describes how to set-up and drill with the LS-100 - a small mud rotary drill rig which has been successfully used in over 20 developing countries around the world with great success.

Drilling With the LS-100 Index

Closely Related Topics Include:

3.1 Introduction

The LS-100 is a small, portable mud rotary drilling machine made by Lone Star Bit Company in Houston, Texas. Using this small drill rig, it is possible to rapidly complete safe, reliable water wells. As discussed by Hamann (1992), advantages of the LS-100 include: comparatively low cost, portability, and speed and depth to which the rig can go relative to manual methods (see Table 2).


Disadvantages of the LS-100 drill rig are that it is limited to drilling a 6 inch borehole to a depth of 30 m (100 ft) and it cannot effectively penetrate hard rock, loose boulders or coarse gravel (an air-rotary version of the LS-100 is currently being developed to drill in these environments).

Table 2: Comparison of Well Construction Techniques
Comparison Factor Hand Digging LS-100 Drilling
Capital CostLowModerate
TechnologyIn-PlaceNew
MethodEstablished, FamiliarSpecial training required.
EffortEffort bonds community.Onus on few drillers
Time to CompleteWeeks or MonthsDays
SafetyCave-in, falling rock hazards
digging in a deep hole.
Nobody in well
ContaminationPoor annular seals; Casing/lid often leak; Shallow water may be contaminated.Protected by sealed hole & continuous casing. Deep, safe aquifers accessible.
DecontaminationDifficultEasy
Water SupplyWell depth limited to 1-2 meters into water table.Well screen 3-10 meters below water table
Water StorageLarge diameter storage augments low yieldCannot construct useful well in low yield aquifers
LimitationsCaving sand or hard rock.Cobbles or hard rock
MaintenanceMinimal equipment; readily available.Spare parts may be difficult to acquire


3.2 Deciding to Drill with the LS-100

A small mud rotary drill rig is only a very small part of a solution to a very large problem. Success in using the drill rig depends on many factors including favourable subsurface geologic conditions, technical aptitude and experience, community support, and a commitment to maintenance, education and communication with others regarding the successes and failures of drilling.

Before you try operating a LS-100 drill rig, it is important that you are familiar with:

In addition, before deciding whether or not to use the LS-100, the following factors should be seriously considered because they have a very strong bearing on the success or failure of a drilling project:

  • Are there people in place who are already drilling using mud rotary techniques? If not, are there people with a mechanical aptitude who are willing to learn how to drill and service the machinery?
  • Are there local people who will be willing and able to maintain the well once it is installed?
  • Are basic supplies (piping, petrol, chlorine) readily available?
  • Is there sufficient technical support available to assist if problems are encountered?
  • Are there adequate communication and transportation options available for the team to function and effectively communicate with you?
  • What equipment, if any (engine spares, well screens, hand pumps, etc) will need to be imported into the country? How reliable is the supply?
  • Is the process of drilling and taking water from a handpump accepted by the prospective users?
  • Do the local people understand the associated costs (time, money and effort)?
  • Are the people committed to actively participate in and complete the project?

3.3 Pre-Drilling Preparations

Prior to traveling to a drilling site, there are a number of tasks which should be done. While it may be sometimes necessary to embark on a drilling project without all these tasks completed, projects will have a higher success rate and a lower level of frustration if they can be done ahead of time. Ideally, people have been trained, an Action Agency and Village Water Committee(s) established, and a Drill Team Selected (see Appendix S).


Maximizing drilling efficiency: Before you leave ensure that:
  1. suitable drilling sites have been selected. Each site should be:
    • in needy areas;
    • located where the LS-100 has a high potential for success;
    • located where drilling has been approved by the required government authorities.
  2. the drill rig, mud pump, pump cylinders and other equipment (such as extra seals for the pump and drill) has cleared customs, is in good repair, is stored in a secure room;
  3. a truck is available to transport the drill machine, handpumps, drilling supplies and drillers to the drilling site each day;
  4. Village Water Committees have been established in each prospective drilling site and that the committee and potential users are supportive of a well being constructed and are willing to take ownership of the project. Before you commit to the job, sign a "Community Water Supply Agreement" (see Appendix R).
  5. Drill crews have the required basic tools and equipment and that all necessary material has been purchased locally or will be brought with the crew to the drill site (see Table 3).

Table 3: Essential Tools and Supplies (pre-drilling shopping list)
Drill crews should have the following basic tools and equipment available prior to heading out to drill a well (these items are normally used to complete the construction of multiple wells):
  1. Thread die & wrench to fit diameter of local hand pump rod.
  2. Four 200-litre (55 gal) drums with tight fitting lids for hauling water to the drill site (water can be used up very fast during drilling and is the main cause of avoidable drilling delays).
  3. Three 19 L (5 gal) pails (buckets).
  4. Two 130x15 cm (2x6) boards to support and level drill rig legs.
  5. Six 1.8m (6ft) long 2x6 or 2x8 boards to build a form for the handpump pad (these can be re-used for future wells).
  6. Six 30-36 cm (12-14 in) lengths of rebar bent at one end to stake down the drill rig legs and guy lines.
  7. 30 m (100 ft) nylon rope to secure casing and pump during installation.
  8. Carpenter's bubble level
  9. 6.4 - 7.6 cm (2.5 - 3 in) diameter bailer, 1.2 m (4 ft) long to develop well.
  10. Socket wrench set with metric and English sockets.
  11. Hack saw blades (high quality).
  12. Wheelbarrow.
  13. Many cloth rags.
  14. 2 shovels, 2 pick-axes.
  15. 3x4 m (8x12 ft) MINIMUM sized heavy gauge plastic sheet to line the mud pits (to prevent water loss) and to put on the ground to keep equipment clean.
  16. First aid box (with basic medical supplies).
The following material should be purchased and stored for Each well that is to be drilled:
  1. 4 sacks bentonite clay or a half a sack of commercial drilling polymer;
  2. 5 lengths of PVC pipe, schedule 40, 10 cm (4 in) dia. 7 m (20 ft) long;
  3. 1 7m (20 ft) length of manufactured wire wrap of PVC screen (or make a screen by slotting a length of casing with a hach saw);
  4. 8 PVC couplings for 10.16 cm (4 in) pipe;
  5. One 10 cm (4 in) dia PVC end cap or make 1 wooden point/end plug;
  6. 1 litre each of PVC cement and primer;
  7. 5 litres (1.3 gallons) liquid bleach to disinfect the well;
  8. 8 sacks of sand for concrete mix (1 sack=50 Kg, 96 lbs or 1.1 cubic ft)
  9. 4 sacks of cement for annual grout seal and handpump pad;
  10. 36 concrete blocks for forming pad edge;
  11. 10 sacks of gravel for concrete mix;
  12. 3 sacks of washed, sieved coarse river gravel (2-6mm dia) for filter pack;
  13. 15m (50 ft) of 1 cm (0.4") diameter reinforced rod or heavy guage wire mesh for the handpump pad base;
  14. 40 litres (10 gallons) gasoline ("petrol") for the drill rig and mud pump engines;
  15. 4 litres (1 gallon) SAE 30 engine oil;
  16. 1 Kg (2 pounds) heavy duty grease for drill pipe joints;
The following material should be purchased and stored for Each handpump that is to be installed:
  1. 5 lengths of 3.18 cm PVC pipe, schedule 40, 7 m (20 ft) long;
  2. 12 PVC couplers (3.18 cm, male-thread with female-glue adapter);
  3. 12 PVC adapters (3.18 cm, female-thread with male-glue adapters);
  4. 10 lengths steel pump rod (1.11 cm dia 3.05 m long 1.11 cm NC threaded ends or 7/16 inch dia, 10 ft long, 7/16 NC threaded ends ) *Stainless steel preferred where water is corrosive;
  5. 12 steel couplings for the pump rod (matching thread).

Well construction in many countries has been complicated by lack of locally available:
  1. Drilling Mud (see Section 5).
  2. PVC Screen and Casing (see Section 7).
  3. Filter Pack Material (see Section 8).

3.4 On-Site Set-up

Unload all tools and equipment on dry ground near the selected drilling location. If possible, orient the drill rig so that it will be shaded during the afternoon. It is very hard to clean sand from greased threads, so keep pipes off the ground by placing them on boards (or tree branches).

Fill four 200 litre (55 gallon) drums with water and ensure that villagers are ready to keep these drums full during the drilling process. Arrange the water drums next to the area where the pits are to be dug. Add 1 cup of chlorine to each drum of water to ensure that bacteria are not injected into the groundwater during drilling - unless you are using polymer to thicken your drilling fluid (see Section 5 - Footnote #1).

Fence off an area behind which all observers must stand during the drilling process. Designate one of the local leaders to ensure that this safety rule is observed at all times. Have one of the drillers frequently explain what is happening while the well is being drilled.

Hand dig a 10 cm (4 in) diameter "well guide hole" about 15 cm (6 in) deep where the well is to be drilled.

3.5 Mud Pit Design/Construction

Dig two pits (settling pit and suction pit) - see Figure 5. Keep these pits 1.5 metres away from the well guide hole so that, when the well is finished, the pump pad does not need to be built on the unstable filled-in mud pits.

Together, the 2 pits should have at least three times the volume of the hole being drilled(1) (Driscoll, 1986). It is usually good if each pit is approximately 60 cm deep, 60 cm wide and 90-120 cm long (2 ft deep, 2 ft wide and 3-4 ft long) (with the long axis parallel to the direction of flow).

If the soil in the pit is sandy or water scarce, line the pits with un-punctured plastic. Wrap the edge of the plastic over and bury it a foot or more into the ground along the flow channels to prevent drilling fluids from flowing beneath the plastic.

Dig a 6 inch deep channel between the well guide hole and the first mud pit. Put the mud pump between the drill rig and the suction mud pit (see Figure 5).

Figure 5: Drilling Equipment Set-up On-Site Set-up

3.6 Drill Rig & Mud Pump Set-up

Set-up the LS-100 and mud pump following the steps outlined below (see Figure 6):

  • Erect the drill rig over the guide hole. Orientate it so that the hoses are over the mud pits, out of the way of the operator, and that the drill table legs are parallel to the channel going from the guide hole to the mud pits. Level the ground around it and install the front and back 2 x 6 boards (see Figure 5).
  • Attach the 3 guy ropes to the drill mast and firmly secure in the ground in a triangular fashion (see Figure 5)). Tighten the ropes to adjust the drill tower for vertical form (use a small carpenters level held against the Mast on two adjacent surfaces).

Connect hoses as follows (see Figure):

  • one hose to the middle port of the 3 way Valve, and the other end to the Mud Pump discharge port (top side);
  • one end of Suction Hose Assembly to suction port of mud pump and lower the foot valve (strainer) into a 18.93 L (5 gal) pail placed in the suction pit (Figure 5). The pail is required to avoid re-circulating cuttings back down the hole;
  • the 1.5 m (5 ft) hose (with both ends fitted) from the top port of the 3-way valve to the side port of the swivel on the drill rig;
  • the fitting end of the by-pass hose that has only one fitting (see Figure 5 and Figure 6) to the bottom port of the 3 way Valve. Allow other end to hang in the settling pit or in the return ditch between borehole and settling pit.

Make sure the crankcases on the drill rig and mud pump engines and transmissions are filled with SAE 30 oil up to the filler hole before you start them! CAUTION: change the oil after the first 5 hours operation for new machines!

The only part of the LS-100 that uses grease is the swivel. Loosen the upper and lower compression nuts of the water entry swivel, remove the 95 mm (3/8 in) bolt from the shaft, and pull out the quill. Apply grease liberally to the inside surfaces of the seals (not the outside of the seals or to the swivel housing). Reinstall the quill, insert the bolt and tighten the lock nut. Tighten the upper compression nut until it is snug. Engage the rotary and, circulating clean water, tighten the compression nut until the quill starts to bind. Then loosen slightly and lock in place using the Allan screw. Repeat tightening procedure for the lower compression nut. Then pump grease into the top and bottom fittings until it is no longer easy to inject grease. Stop if you see grease at the top or bottom of the fittings! If any leaks are observed during rig operation, loosen the set screws and tighten the compression nuts immediately (see Appendix Q to learn more about maintainance).

To prevent the LS-100 engine from stalling when it is idling, adjust the choke as follows prior to initial starting:

  • Remove air filter from carburettor;
  • Pull throttle control cable all the way out;
  • Keeping the throttle in the full open position, move the cable in the direction which will completely close the choke valve in the carburettor. Re-tighten the cable clamp.
  • Raise the drill head (engine/clutch assembly) to a convenient level to pull the starting rope (it is always easiest to start the engine prior to raising the drill head).

Figure 6: LS-100 Set-up
LS-100 Set-up

To keep the LS-100 drive shaft from rotating when the throttle is in the idle position, check and adjust it as follows:

  • With the engine running, turn the throttle control against the stop to the idle position (opposite direction to the choke position);
  • If the output shaft is turning, adjust the idle set screw on the carburettor throttle governor linkage to reduce the RPM to a point where the output shaft stops turning;
  • If necessary, adjust the length of the spring on the governor linkage by either stretching it or bending the ends to shorten it.

Secure a 10 cm (4 in) drill bit on the end of the drill pipe with a pipe wrench after cleaning and lubricating the threads of both the drill pipe and drill bit (see Section 4).

3.7 The Drilling Process

A borehole is drilled by rotating a bit at the end of drill pipe. Borehole cuttings are removed by continuous circulation of a drilling fluid as the bit penetrates the formation. The drill pipe is connected to the drill engine. Drilling fluid is pumped down through the hollow drill pipe using a centrifugal pump (mud pump) to a drill bit. The fluid flows upward in the annular space between the drill pipe and the borehole to the surface where it is channeled into a settling pit and most of the cuttings drop out. Fluid from the settling pit overflows into a second pit (suction pit). Relatively clean fluid from the second pit is then pumped back through the drill pipe and the cycle repeats.

Using water from the 208 litre (55 gallon) drums, fill the mud pits to the very top. Make sure that one person is responsible for keeping the pits full of water during the entire drilling process. This must be done to ensure that the cuttings will settle-out.

Fill the fuel tank of the drill engine and start it. With engine running in idle, raise the drill head to a sufficient height to allow the installation of a drill pipe section with the drill bit. Turn pipe by hand to thread it onto the swivel thread until it is all the way on.

Lower the drill bit into the prepared hand dug guide hole. Allow the drill pipe to rotate above the bottom of the guide hole.

Fill the fuel tank of the mud pump and start it using the following process:

  • Prime the pump before starting the engine by removing the discharge hose or the plug on top of the pump housing and pouring water into this opening until full. It will take a good amount of water since the Suction Hose will also be filled up.
  • Set the choke and run levers to the CHOKE and RUN positions respectively. These control are located on the side of the fuel tank opposite the pump side of the engine.
  • Pull the starting rope (several times may be necessary), and when engine starts to run, immediately return the choke lever to the OFF position. Leave the run lever in the RUN position. Note that it will take a few minutes for the pump to prime.

Increase the engine RPM until the clutch engages and the pipe starts turning. Turn the 3 way Valve so that the water will circulate from the Mud Pump through the bottom by-pass hose back to the pit. Add water as required to top-up the pits.

Then turn the valve so that water flows into the drill swivel. Make sure no water is leaking from the swivel seals. If it is, re-direct the water through the by-pass hole or stop the mud pump. Loosen set screws and tighten gland nuts quite snug and until leaking stops. Re-tighten set screws. It may be necessary to repeat this process during the drilling operation. Pump grease into the top & bottom gland nuts before tightening.

When the water begins pumping through the drill pipe, it will make a lot of splashing so make sure the drill operator is ready to lower the drill pipe into the hole fairly rapidly. After the drill has penetrated 30 cm (1 ft) or so, there will be a smooth flow of water.

Maintain a slight back pressure on the winch handle; at an easy drilling speed, the winch handle should make a full circle every 20 seconds or so. Do not exceed this speed or the water will not be able to circulate the cuttings out of the hole fast enough (causing the bit to seize) and/or the borehole walls will not be coated with enough fines to resist caving ! In harder formations it should make a full circle every 40 seconds. In very hard rock, a drilling rate of 30-150 cm/hr (1 - 5 ft/hr) is to be expected.

In hard rock, insufficient pressure on the drill pipes may result in an extremely low drilling speed. Caution should be used to avoid excessive pull-down pressure (weight) exerted on the drill string because this may result in crooked holes, bent drill rods and jammed drill bits (see Appendix G-3). Rotation speed should be slowed as the pull-down pressure increases.

Watch that the water is circulating continuously when the drill is rotating.

As soon as the drill has penetrated 60 cm (2 ft) or so, take sample cuttings from the first small pit and place them on the appropriate record location.

Continue the drilling process until all 1.5 m (5 ft) of the drill pipe has penetrated the hole.

Leave the drill string turning at the bottom of the hole and continue circulating drill mud until all cuttings are removed from the borehole (even if it takes 5 minutes or longer). This cleaning process is increasingly important as the hole is deepened: if not fully done in the manner described, cuttings may settle to the bottom of the borehole and make it impossible to add another length of drill pipe, cause the hole to cave-in or plug-up (see Appendix G-2) or the drill bit to jamb (see Appendix G-3). Note that the deeper you drill, the longer it takes the cuttings to be removed from the hole.

Switch the 3-way valve so that the drilling fluid circulates back into the mud pits rather than down the drill pipe. Clamp off the drill pipe and unscrew the drill head.

Raise the drill head to the full mast height (be careful not to allow the cable buckle to enter the top hole in the drill mast head and get jammed). If the drill engine is stopped, start it when it is at an easy operating level as the drill head is being raised. Work rapidly to prevent problems caused by cuttings settling in the borehole.

Lubricate the threads of the next drill pipe and screw it into the one clamped at the well head. Screw the other end onto the output shaft. Tighten the joints with wrenches.

Switch the 3-way valve so that the drilling fluid starts to circulate back down the drill pipe. Do not lower the drill head until there is clear evidence that the mud is circulating through the pits again.

Once drilling, it is important to:

  • monitor the drill cuttings to help determine what type of material is being drilled. Take samples of the cuttings every metre or so (at least 1 per drill pipe);
  • clean mud pits frequently to ensure cuttings are not re-circulated;
  • be sure a continuous supply of water is being provided to the 200L (55 gal) drums. Keep water drums replenished.

Special measures must be taken if you drill into:

  • a formation which is very hard to drill (see Appendix G-6).
  • contaminated soil and/or groundwater (see Appendix G-7
  • a confined aquifer which causes water to flow out of the borehole under pressure (see Appendix G-8).

After the 10 cm (4 in) "pilot" borehole is completed to the desired depth, allow the drilling fluid to circulate for 10 minutes to remove as much cuttings as possible from the well.

After 10 minutes, raise the drill head until the slip clamp on the drill table can be engaged at the coupling of the next length of drill pipe. Turn-off the mud pump.

Remove the upper length of drill pipe and lower the drill head to engage the socket in the next length of drill pipe.

Continue to carefully remove the drill pipe from the well. BE SURE THE SLIP CLAMP IS FULLY ENGAGED EACH TIME AND THAT EVERYTHING IS SECURED because it is very easy to drop drill pipe and tools into the borehole! If this happens to you... pray.... and read Appendix G-5!

Be sure to keep the mud pits and borehole full of water during this process.

When all the drill pipe is removed, the crew must now decide if subsurface conditions warrant completing a well. Careful action should be taken if the aquifer is marginal (see Appendix G-9);

If it appears that the borehole has only penetrated a marginal aquifer see section on "When to Stop Drilling" (Section 6), set a 5 cm (2 in) PVC casing with 3 mm (1/8 in) slots in the aquifer area. Then rapidly bail-out the casing, pump it using Waterra tubing or blow-out water using an air compressor (see Section 10.3). If the casing can be easily pumped dry, it may be worthwhile to abandon the well and drill elsewhere.

If there is a good flow from the aquifer, add a 6 inch reamer bit behind the 4 inch bit (see Section 4). Then re-drill the hole to widen it to the required 6 inches. While this is being done, the screen interval, length of casing, volume of gravel pack, grout etc can be planned, materials cut to size etc. This is very helpful to do since time is always of the essence when the drill pipe and bit are pulled from the completed borehole and the screen and casing installed.

If there is much sticky clay, the water-bearing portion of the 10 cm (4 in) hole may be filled with clean sand prior to reaming. This keeps clay from dropping into the borehole and smearing onto the borehole walls (causing severe well development problems).

Replace the drilling fluid with clean water or drilling mud prior to drilling into the aquifer (see "Section 5"). If not done, the well may never reach its full yield!

If in doubt, keep drilling until you are sure that you have found enough water. For tips on "How to Decide When to Stop Drilling", see Section 6.

After you have decided to stop drilling, allow the drilling fluid to circulate for 10 minutes to remove as much cuttings as possible from the well. Then circulate the "mud" out of the borehole by replacing it with fresh (clean) water.

When removing the drill pipe from the well, keep the bit rotating and water circulating. This leaves a nice smooth borehole wall behind the bit as it is coming out of the hole(2).

The casing, gravel pack, annular seal, cement pad and hand pump can then be installed.


3.8 Solutions to Drilling and Well Problems

There are many problems that you will encounter when drilling wells. Learn from the problems and try not to repeat them too often!

You will have more success if you keep in mind the following 5 common problems which lead to unsuccessful well completion:
  1. Drilling in conditions beyond equipment capability (Section 3.1);
  2. Unsuitable Drilling Mud and Borehole Caving (see Appendix G-2);
  3. Failure to get casing to bottom of borehole (see Appendix G-10));
  4. Poor gravel pack (see Section 8);
  5. Inadequate well development (see Section 10);



In addition, the following problems have also been encountered:




Footnotes

1 Ideally, for a 30 m (100 ft) deep borehole drilled with the LS-100, the settling pit should be 60 cm (2 ft) deep, 75 cm (2.5 ft) wide and 2 m (6 ft) long; the suction pit should be 60 cm (2 ft) deep, 75 cm (2.5 ft) wide and 1 m (3 ft) long. However, while these pits provide optimum settling capability, they require large quantities of water to be brought to the site.

2 If this is not done, the fins of the blade bit may disturb the borehole wall and cause silt/clay cuttings to "ball-up" or bridge within the borehole. In addition, drilling fluid may cause silts and clays (especially above the water table) to swell and bulge into the borehole. Getting the screen past these blockages can be very difficult and it is almost impossible to avoid severely plugging the screen.

Brush, R. (197?) "Wells Construction: Hand Dug and Hand Drilled", US Peace Corps, Washington DC.

Driscoll, F. (1986) Groundwater and Wells, St. Paul: Johnson Division

Hamann, M. (1992) "Utilization of Small Mud Rotary Drilling Rigs for Development of Safe, Village-Level Groundwater Resources", Paper presented at the 5th African Water Technology Conference, Nairobi, Kenya, February, 1992.

Lovett, W. (1985) "Chapter 2 - Safety on the Job", pp. 9-12 in Water Well Driller's Beginning Training Manual, Worthington, OH: National Water Well Association, ISBN 1-56034-049-5.

Moffat, B. (198?) "Efficient Water Wells", Developing World Water", Hong Kong: Grosvenor Press Int'l, pp. 36-37.

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