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A borehole is the generalised term for any narrow shaft drilled in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water or other liquid (such as petroleum) or gases (such as natural gas), as part of a geotechnical investigation or environmental site assessment, for mineral exploration, or as a pilot hole for installing piers or underground utilities. Boreholes used as water wells are described in more depth in that section.
In the engineering and environmental consulting fields, the term is used to collectively describe all of the various types of holes drilled as part of a geotechnical investigation or environmental site assessment. This includes holes advanced to collect soil samples, water samples or rock cores, to advance in situ sampling equipment, or to install monitoring wells or piezometers. Samples collected from boreholes are often tested in a laboratory to determine their physical properties, or to assess levels of various chemical constituents or contaminants.
Typically, a borehole used as a well is completed by installing a vertical pipe (casing) and well screen to keep the borehole from collapsing. This also helps prevent surface contaminants from entering the borehole and protects any installed pump from drawing in sand and sediment. When completed in this manner the borehole is then more commonly called a well: whether it is a water well, oil well or natural gas extraction well.
Drilling has undergone a substantial evolution from the early days and is now a very specialised and technical activity requiring substantial skill and professional expertise to achieve the desired result.
There are various methods for drilling a borehole but the most common methods used today are rotary drilling, percussion drilling and sonic drilling. With the exception of sonic drilling, there are different methods for each of the other categories. In addition there are also different flushing methods for the removal of cuttings from the borehole i.e. direct flush or reverse flush and different and different flushing media such as air, foam or mud. In the case of percussion the cuttings are removed by mechanical methods. Possibly the most common drilling methods used is the rotary method utilising air or mud flush. Using the rotary method with air flush and an air operated hammer (percussion) mounted in the drill string has the advantage of being fast, efficient and very controllable. However, different situations may require different applications, technologies and methodologies to reach a successful project completion, and that's where the industry experience and expertise of the Drilcorp team can help. With their skill and knowledge, you can avoid expensive mistakes in your project and rest assured that your borehole will be successfully drilled on time and within budget.
Groundwater Abstraction Boreholes
When drilling a borehole that will ultimately be used for groundwater abstraction purposes, the process becomes much more than just making a hole in the ground.
A water borehole is a specially engineered hole in the ground, designed to allow water to flow into this hole and permitting a pump to be installed inside the hole to facilitate the abstraction of water. Critical to this engineered design are the steps taken to prevent the surrounding geological formations to collapse and seal off the borehole, which could result in the entire borehole drilling process being started from scratch, or at a minimum, cleaning out the hole to recommission it.
Water abstraction is a team effort; the driller is there to drill and construct a borehole, while the actual location of the water is a task that is carried out by the scientific team members, led by a hydrogeologist. The scientists have to study the geological formations and determine how and where the driller should install the borehole. At Drilcorp we have the best drillers working with the most accomplished scientists; which together make a formidable team.
One of the most important aspects of drilling is the absolute necessity to achieve a vertical borehole. The skill involved in maintaining a vertical borehole as the drill passes though sand, gravel, clay and hard rock formations to its final destination is one that is only acquired through many years of drilling experience.
Drill rods can weigh several tons and if too much pressure is applied while drilling or the drill spins too quickly, it can wear out the bit or overload the rig. Conversely if insufficient pressure is applied or the spin speed is too slow, it may not penetrate the rock. Add to this the complication that several different geological types of strata may be encountered in a single borehole installation, requiring differing drill pressures and spin speeds and you can see why this is a task for experienced operators, and why Drilcorp put so much emphasis on experience and training in their workforce.
Because the drill rods are quite heavy and can weigh several tons; if the drill pushes too hard or turns too fast, the drill bit will wear out too fast; if it does not push hard enough, it won't penetrate. Quite often several rock layers are encountered in a single borehole, each requiring different drilling pressures and speeds. When water is encountered the drilling becomes even more complex, with the driller having to use his expertise to make vital adjustments to the pressures and drill speeds in a very short timescale.
The two main types of drilling are:
Rotary drilling using the mud flush technique.
In rotary drilling, a drill bit, which is made from toughened materials such as tungsten, is attached to a drill pipe. Once drilling has commenced and the bit is breaking through the substrata, the drill fluids are circulated through the drilling pipework into the borehole and back to the surface, at the same time washing the drilling residue or cuttings upwards and out of the hole. This fluid also serves as a formation stabiliser preventing possible cave-in of unstable sands or crumbly rock before the well casing or well screen is installed. In addition this fluid acts as a lubricant for the drill bit. As the drill passes through water bearing rock formations water will flow into the hole. Drillers, or hydrogeologists on site will carefully monitor the depth of water "strikes" and keep a note of the formations in which they occur.
Rotary drilling using air percussion and flush technique
This technique uses compressed air to operate a down-hole air hammer on the end of the drill string that helps to break up the rock formation. The compressed air that is used to operate the down-hole air hammer also blows the crushed rock fragments out of the hole to the surface along with any water that flows into the hole during drilling. An experienced driller will realise that water will flow from the hole at specific intervals can be caused by the compressed air forcing minor water deposits to the surface. Only when the driller is certain that he has reached the right aquifer will he stop the drilling process.
Costs
The cost of a borehole can be significantly influenced by the applied design as well as the difficulty to construct a borehole in a specific geological formation.
Drilcorp will advise you of the most cost-effective method of drilling a borehole after they have carried out a primary site survey.
While our solution may not be the cheapest in initial costs, in the long term we will provide you with a solution that will repay its investment many times over.
Drilcorp will specify systems, applications and construction methods that will ensure the maximum functionality and longevity of your installation, keeping it clean, functional and operational for many years to come with the minimum of maintenance.
Drilcorp's reputation is second to none, our services are actively sought and retained by some of the most prestigious companies in the World and our byword is excellence in service and delivery.
Call us now on 0191 527 3970 for a no-obligation quotation.
In the engineering and environmental consulting fields, the term is used to collectively describe all of the various types of holes drilled as part of a geotechnical investigation or environmental site assessment. This includes holes advanced to collect soil samples, water samples or rock cores, to advance in situ sampling equipment, or to install monitoring wells or piezometers. Samples collected from boreholes are often tested in a laboratory to determine their physical properties, or to assess levels of various chemical constituents or contaminants.
Typically, a borehole used as a well is completed by installing a vertical pipe (casing) and well screen to keep the borehole from collapsing. This also helps prevent surface contaminants from entering the borehole and protects any installed pump from drawing in sand and sediment. When completed in this manner the borehole is then more commonly called a well: whether it is a water well, oil well or natural gas extraction well.
Drilling has undergone a substantial evolution from the early days and is now a very specialised and technical activity requiring substantial skill and professional expertise to achieve the desired result.
There are various methods for drilling a borehole but the most common methods used today are rotary drilling, percussion drilling and sonic drilling. With the exception of sonic drilling, there are different methods for each of the other categories. In addition there are also different flushing methods for the removal of cuttings from the borehole i.e. direct flush or reverse flush and different and different flushing media such as air, foam or mud. In the case of percussion the cuttings are removed by mechanical methods. Possibly the most common drilling methods used is the rotary method utilising air or mud flush. Using the rotary method with air flush and an air operated hammer (percussion) mounted in the drill string has the advantage of being fast, efficient and very controllable. However, different situations may require different applications, technologies and methodologies to reach a successful project completion, and that's where the industry experience and expertise of the Drilcorp team can help. With their skill and knowledge, you can avoid expensive mistakes in your project and rest assured that your borehole will be successfully drilled on time and within budget.
Groundwater Abstraction Boreholes
When drilling a borehole that will ultimately be used for groundwater abstraction purposes, the process becomes much more than just making a hole in the ground.
A water borehole is a specially engineered hole in the ground, designed to allow water to flow into this hole and permitting a pump to be installed inside the hole to facilitate the abstraction of water. Critical to this engineered design are the steps taken to prevent the surrounding geological formations to collapse and seal off the borehole, which could result in the entire borehole drilling process being started from scratch, or at a minimum, cleaning out the hole to recommission it.
Water abstraction is a team effort; the driller is there to drill and construct a borehole, while the actual location of the water is a task that is carried out by the scientific team members, led by a hydrogeologist. The scientists have to study the geological formations and determine how and where the driller should install the borehole. At Drilcorp we have the best drillers working with the most accomplished scientists; which together make a formidable team.
One of the most important aspects of drilling is the absolute necessity to achieve a vertical borehole. The skill involved in maintaining a vertical borehole as the drill passes though sand, gravel, clay and hard rock formations to its final destination is one that is only acquired through many years of drilling experience.
Drill rods can weigh several tons and if too much pressure is applied while drilling or the drill spins too quickly, it can wear out the bit or overload the rig. Conversely if insufficient pressure is applied or the spin speed is too slow, it may not penetrate the rock. Add to this the complication that several different geological types of strata may be encountered in a single borehole installation, requiring differing drill pressures and spin speeds and you can see why this is a task for experienced operators, and why Drilcorp put so much emphasis on experience and training in their workforce.
Because the drill rods are quite heavy and can weigh several tons; if the drill pushes too hard or turns too fast, the drill bit will wear out too fast; if it does not push hard enough, it won't penetrate. Quite often several rock layers are encountered in a single borehole, each requiring different drilling pressures and speeds. When water is encountered the drilling becomes even more complex, with the driller having to use his expertise to make vital adjustments to the pressures and drill speeds in a very short timescale.
The two main types of drilling are:
Rotary drilling using the mud flush technique.
In rotary drilling, a drill bit, which is made from toughened materials such as tungsten, is attached to a drill pipe. Once drilling has commenced and the bit is breaking through the substrata, the drill fluids are circulated through the drilling pipework into the borehole and back to the surface, at the same time washing the drilling residue or cuttings upwards and out of the hole. This fluid also serves as a formation stabiliser preventing possible cave-in of unstable sands or crumbly rock before the well casing or well screen is installed. In addition this fluid acts as a lubricant for the drill bit. As the drill passes through water bearing rock formations water will flow into the hole. Drillers, or hydrogeologists on site will carefully monitor the depth of water "strikes" and keep a note of the formations in which they occur.
Rotary drilling using air percussion and flush technique
This technique uses compressed air to operate a down-hole air hammer on the end of the drill string that helps to break up the rock formation. The compressed air that is used to operate the down-hole air hammer also blows the crushed rock fragments out of the hole to the surface along with any water that flows into the hole during drilling. An experienced driller will realise that water will flow from the hole at specific intervals can be caused by the compressed air forcing minor water deposits to the surface. Only when the driller is certain that he has reached the right aquifer will he stop the drilling process.
Costs
The cost of a borehole can be significantly influenced by the applied design as well as the difficulty to construct a borehole in a specific geological formation.
Drilcorp will advise you of the most cost-effective method of drilling a borehole after they have carried out a primary site survey.
While our solution may not be the cheapest in initial costs, in the long term we will provide you with a solution that will repay its investment many times over.
Drilcorp will specify systems, applications and construction methods that will ensure the maximum functionality and longevity of your installation, keeping it clean, functional and operational for many years to come with the minimum of maintenance.
Drilcorp's reputation is second to none, our services are actively sought and retained by some of the most prestigious companies in the World and our byword is excellence in service and delivery.
Call us now on 0191 527 3970 for a no-obligation quotation.
