If you&#;re familiar with drilling at all, you know it&#;s all about the geology. It&#;s no different when drilling for water wells. Rock formation type, depth of the overburden, bedrock and the aquifer all play a role in how you determine the method of drilling and which equipment and drill bits you need. You might need roller cone bits, step drag bits, claw bits, chevron bits or PDC bits for water well drilling, but it&#;s dependent on the application.
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If you already know what type of bit you need, contact our team to make an order. O-K Bit is the world&#;s largest supplier of rerun bits, and we&#;re happy to provide you with whichever bits you&#;re looking for.
Types of Water Wells
While you are probably interested in information about how water wells are drilled and what bits you may need, it&#;s important to note that drilled wells are not the only type of water wells.
There are three primary types of water wells: drilled wells, dug wells and driven wells. Each has its own unique characteristics.
Drilled Wells &#; Drilled water wells utilize a drilling rig and drill bits to bore into the earth. The bit rotates clockwise to create the borehole. As the bit breaks up the soil and rock beneath, the wells are drilled deep into the ground (often between 100 and 500 feet).
Dug Wells &#; Dug wells are water wells that are created by digging a hole in the ground and lining the walls of the hole with brick, tile or stone. The hole is drilled to a level below the water table so that the water comes into the hole and can be bailed out.
Driven Wells &#; These wells are made by driving pipe into the ground. Driven wells are relatively shallow (30 to 50 feet deep) and, therefore, they draw in water that is in aquifers close to the surface.
All three types of wells penetrate below the water table into the aquifer below (although to different depths). The water from the aquifer is then pumped or bailed out through the well. However, driven wells and dug wells are more likely to be contaminated because they draw water from shallower depths which are more likely to have bacteria or contamination.
How are water wells drilled?
Drilling water wells is a process that involves many steps. The lengthy process is valuable though because, if done correctly, a water well can provide water for a hundred years or longer. The process also helps drillers ensure they are equipped with the right tools and drill bits for successfully drilling the well.
Steps for drilling a water well:
Identify the desired location &#; Before beginning the process, it&#;s important to identify the well&#;s location and ensure an adequate supply of groundwater. If there is not an adequate water supply or the correct directional flow of water, you may need to select a different site.
Evaluate the site of the well &#; evaluating the site is an important step for determining the desired depth of the well, understanding the rock formations present and selecting the equipment needed for the well. This includes choosing the correct drill bits for your water well drilling site.
Drilling the well &#; drilling the well will involve setting up the drilling rig, drilling the borehole and installing the casing and screen.
Pumping and evaluating &#; after the drilling, the pumped yield of the well will be evaluated and then developed. For most wells, there will be fine materials (minerals and sediment) that need to be removed so the water more effectively moves into the well.
Testing and disinfecting &#; The water will then be tested for quantity and quality. The well will be disinfected. After the water well is successfully drilled, it will be capped (for sanitary protection) until it can be connected to the customer&#;s system.
Bits Used for Water Well Drilling
A wide variety of drill bits are used for water well drilling. The rock formations of the drilling site will determine which bits are needed, but the O-K Bit team is equipped with whichever water well drill bits you need.
The following bits are commonly used for water well drilling:
Step Drag Bits
Step drag bits are commonly used for drilling pilot holes. They are useful in this application because their cuttings are easiest to log and they are able to drill quickly. They are durable and hard, which means they have the longevity that many other bit types lack. Step bits are also used in sand, clay and other medium-hard rock formations throughout the drilling process. You should avoid using step bits in hard or coarse gravel rock formations because they will not be able to shear effectively.
Roller Cone Bits
Roller cone bits are identifiable by their rolling cone inserts. These cutting structures are useful for drilling through tough soil and rock. The tungsten carbide inserts are durable and self-cleaning, so as they crush and chip hard rock formations they remain productive. These bits are used at lower penetration rates, but they are especially effective at breaking up hard rock.
PDC Bits (Polycrystalline Diamond Compact Bits)
You may use a PDC bit for a water well drilling application if you hope to drill very precisely in soft to medium rock formations. These bits utilize a synthetic diamond compound on the cutters to create a highly durable and productive cutting structure on the bit. PDC bits are able to achieve high penetration rates while in use.
Claw Bits
If your water well drilling site has a high volume of clay, a claw bit may be useful as you drill your water well. A claw bit is designed to use its uniquely shaped fingers to dig into and loosen hard clay that otherwise would be difficult to bore through. These bits are highly durable and the cutting structures (the fingers) can be replaced when worn.
Reamer Bits
Finally, reamer bits are often used in water well drilling to widen the borehole and keep the hole straight. The cutting surfaces of these bits are attached below drill pipe which then aids in keeping the hole straight and prevents bits from becoming gummed up with clay. Most commonly, reamer bits are used in sandy soils or clay formations.
Well Drilling Methods
There are a wide variety of well drilling methods and techniques. The best approach will likely depend on the unique conditions of your drilling site. A few of these methods are:
Regardless of the method or location of your water well drilling, O-K Bit is here to help you select the best new and rerun bits for the job. Contact our team today to order the supplies you need for water well drilling.
Drilling type
Soil type
Comments
Rotary drilling
Soft rock
Significant depths up to 5,000 meters
Possibility of inclined or horizontal drilling
Down-the-hole drilling
Hard and cracked rock (limestone, granite, etc.)
Depth up to 4,000 meters
Top hammer drilling
Consolidated land
Small diameter (150 mm maximum), shallow depth
Able to do inclined drilling
Auger drilling
Clay, clayey sand, gravel
Depth of a few dozen meters
Core drilling
All soil types
Drilling for soil analysis
Able to do inclined drilling
Percussion drilling
Hard rock: sandstone, limestone, shale
Depth up to 100 meters
Pipe Jacking
Clay, clayey sand, gravel
Installation of horizontal or vertical pipes
Rotary drilling: This type of drilling digs a hole by grinding the rock with a tool under the effect of weight and rotation. It is mainly used in oil production. The cuttings are brought to the surface under the pressure of a drilling fluid that is injected into the drill string. Drilling fluid also helps consolidate the walls of the borehole, so it is not necessary to case it as the operation progresses.
Down-the-hole drilling (rotary percussion drilling or rotary hammer drilling): this type of drilling uses drilling rigs that drill with a rotary cutter (drill head) and hammer the bottom of the hole with a pneumatic hammer. The excavated material rises to the surface under the pressure of the compressed air used for the hammer. These drilling rigs are powerful and have high drilling rates, especially in rock. For artesian wells (wells where water naturally rises to the surface under groundwater pressure) or geothermal drilling, an air injection at the end of the drill pipe pushes the water up the borehole, allowing the operator to immediately determine the water flow encountered. This type of drilling is used for hard and cracked ground up to 4,000 meters deep. When the drilling bit is eccentric, the drilling can be done with a casing advancement system (installation of tubes by gravity) which reinforces the hole as the drilling progresses.
Top hammer drilling: this type of drilling uses drilling rigs that also operate on a percussion system, but one that remains outside the borehole. They are mainly used for small diameter drilling, for example for mineral exploration or the installation of tie rods in rock. This system is used for shallow boreholes, as there can be significant deviation due to the structure of the ground drilled through. These drilling rigs can operate in any direction however.
Auger boring: This is a type of rotary drilling using a worm screw (the auger). This type of drilling is mainly used for unconsolidated clay or sand terrain. The excavated material is directly brought to the surface by the worm screw. For deep drilling, it may be necessary to regularly raise the auger to empty it of its excavated material.
Core drilling: Core drilling is similar to rotary drilling, but it uses a crown to extract a sample, called a core, inside the tool.
Percussion drilling: consists in breaking the rock by dropping a tool, the drill bit, by gravity. This type of drilling can only be used vertically. To prevent the borehole from collapsing, it is necessary to case it as it is drilled. The cuttings are reassembled as soon as they interfere with drilling by replacing the drill bit with a flap valve bailer. The flap valve bailer is a type of tube equipped with a tilting flap in the lower part. This tilting flap allows the tube to be filled with excavated material which is then transported to the surface.
Pipe jacking: is mainly used to install horizontal pipes. The tube is pushed progressively by percussion, the excavated material being removed at the end of the drilling operation either by water injection or with an auger. This technique is used in particular to avoid transmitting vibrations to the surrounding buildings or to avoid digging a trench.
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