Boreholes

Location of the hidden sea

Divining

Divining or dowsing has been used for centuries to locate ground water and minerals. The practice usually utilizes common instruments such as bent wire, forked rods, bottles, pendulums and many other utensils. The process is done by walking over an area with an instrument held in the hand; the diviner then senses changes below the ground by a reaction on the instrument. The instrument supposedly reacts to underlying water or minerals. There are many divining methods utilized around the world and they all differ from one another. To date there is little proof that this practice actually works. There is no scientific proof that divining locates water and minerals, it is believed that divining methods respond to changes in the earths magnetism and not water or minerals. However science can also not disprove water divining due to the many successful recordings.

There are many

diviners who have a proven track record and should be able to prove their strike record. These diviners are rare and sometimes difficult to obtain. It is not common for diviners to have recorded data on there boreholes but there reputation normally speaks for itself. Very few diviners will have a success rate above 70 to 80 percent.

It is important that you question the diviner on his knowledge of the area and the average depth of the boreholes. This information can give you an idea on the costs of the drilling. This is an approximate and should not be held as the actual final depth of drilling.

Throwing the hat

There are many successful boreholes that have been located with the random guess method. This method can be used in reas where ground water is easily located and the geology suitable. It has also been used in residential areas where limited access is common. This approach must be used with caution in areas where ground water is scarce. When using this approach make sure you know enough on the geology and success possibilities.

Scientific approach.

This approach uses geophysics and a scientific approach usually conducted by a hydro geologist. This method is utilized on larger projects where large volumes of water are required and a full report needed for sustainable abstraction. The methods used to locate the ground water will differ according to the geology. The instruments used to locate possible ground water features require a relatively competent person to operate the equipment or the information is worthless as well as the investigation.These geophysical instruments are extremely sensitive to interference and cannot operate in confined residential areas. There are many companies that conduct geophysical surveys and they all have proven track records. It is advisable that a local company be selected as they may know the area and its true production characteristics.

Hydrology

All of the methods used to locate ground water require some understanding of the surrounding geology. In areas where there are sustainable aquifers the possibilities for successful boreholes are greater and less attention need be spent on borehole siting. The areas where lower rainfall and poorer geology are common the possibilities reduce drastically. These areas require greater understanding and attention. Hydrology is the base of any ground water drilling project and should not be overlooked.

Drilling of water supply boreholes.

A borehole is an investment. A successful borehole is an investment that pays for itself time and time again. A borehole improves property value
anywhere in the world. The initial cost of a borehole is the minimal cost over the useful life of the installation. A water borehole can only maximize its cost saving if the installation is based on sound design and engineering. The project should be based on maximizing continuous savings. The initial cost saving on the installation will become the long term failure of not achieving long term cost savings and may even cause financial losses. It is the running costs of the installation that become the largest costs when the design is incorrect. The energy costs can also play a significant roll over a long period of time. It is the combination of good design and installation practices that make a borehole a sound investment.

The initial steps one should assess.

Before a borehole is drilled the reasons for drilling should be well assessed. The costs of drilling and equipping a producing water borehole can become very costly. In some cases this has to be overlooked, a good example of this is a subsistence borehole where the installation is only used for domestic purposes. Subsistence boreholes very rarely recover their initial as well as long term running costs. Boreholes that are drilled to supply good quality water for irrigation, industry and general human use, almost always recover their total input costs...

Drilling methods for water boreholes.

Percussion drilling.

This is one of the oldest drilling methods used by man. Its operation is simple and effective. The basic principle of its operation makes this drilling method very useful in developing countries. The drill rigs are cheaper than most modern drilling methods and equipment. Percussion drilling is extremely slow and is best suited to rural areas where limited resources are available. The drilling of the borehole is achieved by a set of drilling tools attached to a steel cable, the set of drill tools are moved in an up and down motion, it is on the downward motion that the
bit strikes the formation face. As the bit strikes the surface it chips or crushes the material being drilled. The drill string reciprocates at 20 to 60 times a minute. The drilling is almost always conducted in water filled boreholes. The borehole must be filled with water in order to form a drilling sludge which is then removed with a bailer.

The sludge is the drilled material and waste product.

The borehole is bailed as soon as the sludge becomes too thick to continue drilling. Once the borehole has been bailed it is refilled with water and the drill string is then reinserted to continue the drilling process. Percussion drilling can be used to drill almost any type of geology. It is however best suited to softer drilling conditions.

Rotary drilling.

There are many drilling methods that use the rotary method. The rotary drilling method uses a string of drill rods screwed together. The drill string is rotated hydraulically or mechanically. As the drill string rotates the drill bit advances. This more modern method is used with much diversity and can be customized to suit the drilling conditions.

Rotary mud drilling

The mud drilling method uses mud as the drilling fluid. The mud rotary drilling method is commonly used in unconsolidated soft formations. It is used when the geology has a tendency to collapse when left unstabilized. The mud fluid is used as the temporary open whole stabilizer. The mud is pumped through the drill rods to the drill bit via a pump on the drill rig, as the mud exits the bit it collects the drilled material The drilling fluid
moves out of the borehole as it circulated. Once the cuttings reach the surface the cuttings are removed out of the drilling mud via a settling pit. Once the mud is cleaned to its original condition it is recalculated.

This drilling method can become very costly due to the mud additives required to tune the mud to its optimum drilling performance. The mud rotary method is also used in deep hard rock water and oil wells. Mud rotary drilling is one of the most complicated drilling methods used; It is for this reason that mud drilling is less common in developing areas. Mud fluid can also damage the surrounding formation if it is not correctly monitored.

Air rotary drilling

The air drilling method uses air as the drilling and circulating fluid. This method requires a compressor with a high volume and pressure to supply sufficient air for effective drilling. The compressed air is pumped through the drill rods to the drilling bit. Once the compressed air exits the bit it collects the cuttings and begins expanding in an upward direction or towards the lower pressure in the borehole. As the air expands it energy output increases, therefore allowing the air to carry cuttings and solids. Once the air exits the borehole the energy dissipates and the cuttings are left on the surface as sand or rock chips. Air is located any where, where drilling is required. It is also much more simplistic in character as supposed to a liquid drilling fluid. The characteristics of air can be altered by adding chemical components to the compressed air. By adding water, foam and surficant we change the air density and volume allowing for improved cleaning of the borehole. Air rotary drilling is best suited for medium to hard drilling in consolidated formations. This method is commonly used on blast holes and some larger water wells.

Rotary percussion drilling or Down hole hammer

Down the hole hammer DTH drilling uses compressed air to power a percussion tool attached above the drill bit. As the piston strikes the bit the energy is transmitted into the rock, this strike causes the rock to shatter. Each time the hammer strikes the drill bit, the bit face is rotated to a new position. A down the hole hammer can strike the bit at 2000 to 4000 blows per minute. The rest of the drilling method follows the same principals as air rotary drilling. This drilling method is best suited to hard rock drilling as well as medium consolidated formations. DTH drilling is one of the most common drilling methods used.

In water exploration and abstraction borehole construction..

Alternative methods

There are many methods that are currently in use that create water boreholes. These methods are usually simplistic and require unsophisticated equipment. Most of these methods target shallow aquifers. These drilling methods are limited to rural and costal areas with some exceptions.