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DRILLING TECHNIQUE

The construction of drilling has a very extensive literature and years of experience, mainly acquired from the sector of deep oil drilling.

If a project is not properly designed from the beginning and not constructed in the right way according to scientific parameters, it has a high risk of failure.

First, we do a preliminary investigation of the wider study area. For this purpose, we collect various data of the area, such as geological and hydrogeological maps, aerial photographs, hydrogeological and environmental studies, data concerning the characteristics of existing already completed boreholes. Also, if deemed necessary, a preliminary on-site visit is made to the study area.

By processing and combining all the above data, we achieve the best estimate and more accurate approach of the technical method, drilling specifications and drilling equipment, which will be selected for the construction of the project.

1. DRILLING METHODS

Depending on the rocks that are expected to be drilled, we choose between two main drilling methods:

  • one that uses a material that is technically called mud, as a circulation pulp. This method is chosen when relatively loose materials with a chance to collapse are expected to be drilled.
  • the one that uses foam material (soap) and air compressor, in cases of drilling mainly hard rocks.

More specifically, the mud is created when we apply drilling in clay rocks, mainly in recent geological formations. Occasionally we may need to add active solids (bentonite) to enhance the viscosity. We may also need to add inert solids (baryte) to achieve density and polymers – additives to improve its flow properties.

The composition of the mud and the way it is used play the most important role in the construction of the boreholes, which are constructed in this way. Indicatively, we mention that chemist responsible for the mud is the “project leader” in the field of oil drilling.

The mud circulation circuit must be made in such a way that it does not lose its properties. To achieve this requires large and complex machines (vibrating sieves, hydrocyclones, centrifugal separators, baffle tanks, etc.).

In order to use the above machines, an elevated ramp is required, on which a drilling rig is installed. However, because this is often impossible for technical reasons, the mud circuit can be constructed in the ground in a suitable way and techniques (with meander-shaped wells, pits, baffles, screens, etc.). In this way we get quite close to the result, which we would achieve with the use of machines.

If the purity of the circulation mud and its proper chemistry are not achieved, the drilling may fail.

The second method is mainly used in hard rocks with the help of air compressor and soapy foam material. The foam produced has the property of swelling and creating great buoyancy, as a result of which it cleans the drilling from the drilling material.

2. DRILLING

The bits used during drilling are selected according to the rocks encountered by the drilling and depending on their hardness.

In hard rocks, in which the method with foam material and air compressor is chosen, the drilling can be done using an air hammer.

Initially, a hosting pipe of larger diameter than the final borehole diameter and depth is installed according to the original design or the results of the initial drilling. The exterior pipe is cemented with ariani (diluted cement mortar).

The perforation is made internally by the sealing tube. A suitable guide 0.5-1 inches  diameter is used, smaller than the size of the bit and counterweights, which are necessary for better alignment and verticality of the drilling.

During drilling, samples of the geological formations are taken every 3 meters approximately, as well as at each change of lithological type. The samples are stored in special wooden boxes, in order to be available for supervision.

At the end of the work, the samples are transferred for storage. The samples are characterized and recorded at the drilling section by our geologist.

The correct characterization and the exact matching of their depth, is a decisive factor for the best placement of the filter pipes and the best possible quantitative and qualitative result of the drilling. For example, if the filters tubes are placed against clay and sand and the “blind” tubes against gravel containing water, we will result in reduced quantity and poor quality, due to the inflow of sand. The result will be the rapid destruction of the pumping unit, as well as the borehole.

3. GEOPHYSICAL RECORDINGS – DELETE (LOGGING)

Our company can perform electrical borehole logging, which help to accurately locate the aquifers, the correct placement of the filter pipes and the control, in the first phase, of the water quality of the perforated aquifers (brackish water). Geophysical surveying is done in tubular drilling, using a projectile that records electrical resistance , spontaneous potential and natural gamma radiation. The recordings are made immediately after the end of the drilling starting from the bottom of the drilling rig, towards the surface. Our company also has an underwater camera that descends into a tubed clean borehole.

4. DEVELOPMENT (CLEANING) OF THE WATER DRILL

In case of use of mud in the drilling, when the installation of the pipes and the gravel filter is completed, it is followed by cleaning with clean water and using a packer from the bottom of the drilling upwards, in order to achieve the cleaning of all pipes and gravel filter throughout depth.

If no packer is used, the drill is washed outside the pipes, only in the part from the first filter (the filter closest to the ground surface) to the surface. All other filters from there and below will not be washed externally, due to water leakage in the first filter. That is, the drilling will not be washed!

During the development of the drilling, if required, an air compressor will be used for the best possible result (air lift).

5. TECHNICAL REPORT

After the end of the field work, we prepare and submit to you in two (2) copies a project file, which contains all the information of the drilled mine.

The project portfolio will contain:

  1. Summary report, which includes a description of the work and methods used for the drilling that was constructed. It also contains elements such as the speed of the drilling rig, the losses of circulation pulp, the hydrostatic level after the development of the drilling rig as well as any other data for the works of the project.
  2. Drilling columns and piping sections, which include the geological description of the rocks drilled, the diameters of drilling and piping and the depth of installation of filter pipes, etc.
  3. Processing and presentation of the results of the test pumps, test pump vouchers, critical flow diagrams. Semilogarithmic diagrams of fall and level return as a function of time and calculation of hydraulic parameters, exploitable flow and the corresponding pumping level.

Responsible for the project will be the signatory Geologist of our company, with extensive experience in the design and construction of even the most specialized drilling projects.

Our construction sites are insured against any risk in a private insurance company.