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Our Earth disposes of several fossil fuels such as oil, the most common resource used for transportation, or coal, which is mostly used in the industrial sector.
However, there is another type of fuel which we use on a daily basis to produce energy in power plants or even to heat up our own houses: we are talking about Natural Gas!
Fossilised natural gas can be found in deposits and it is produced from the anaerobic decomposition of organic material. It is mostly composed of methane, the smallest out of all hydrocarbon molecules. However, it can contain also ethane, propane and butane, as well as small quantities of pentane.
There are many gas fields and they are present almost all over the globe. The largest supplier is the Country of Russia, with a staggering yearly production of 624,61 Gm3 of natural gas. According to a 2010 estimate, its reserves will last at least for another 74 years. In second place, we find the Countries of Iran and Qatar, with a yearly production that ranges between 120 and 150 Gm3.
Anyway, how is natural gas extracted?
Most of the times natural gas is located in presence of a coal filed. This happens because over the years the decomposition of organic material caused the formation of layers of peat in river and torrential areas. Coal, and natural gas were generated through the fossilization of the peat layers .
Before starting with the extraction, it is necessary to carry out inspections on the territory in order to: determine the size of the field, the amount of gas present and the feasibility of the process of extraction. Geologists and geophysicists carry out tests on the reservoir site to digitally recreate the subsoil in 3D using a technique called Seismic Reflection: a sort of scan of the soil. This technique consists of firing seismic waves which, reflecting on the underlying clayey layers, are able to graphically reproduce the subsoil, highlighting potential natural gas deposits. After this initial procedure, we continue by drilling an exploration well, to make sure that the gas in present in this area. Subsequently, other types of wells are drilled, called delimitation wells. These have the function to delimit, both vertically and horizontally, the effective extent of the gas field, in order to have a precise assessment of the amount of gas. This is to ensure a fair economic return to the company that invests in a particular field.
Once the quantity of gas that the field contains have been verified, we move on to the next step, which consists in drawing up a Development Plan. The development plan will decide: how many extraction wells have to be drilled on the site, in which position, with which trajectory, the type of well (vertical, horizontal or deviated), as well as the position and number of structures necessary for the management and transport of the extracted gas
The type of the structure built to extract the gas can vary depending on the location of the field: hen the reservoir is close enough to the earth’s surface, the construction of the site and the gas extraction are easier. However, sometimes the deposit may be located under the seabed. In this case, the preparation of the site is more complex. It is necessary to build a platform in the middle of the sea, an ‘Off-shore’ platform, from which all drilling and extraction operations can be managed.
However, there is another type of fuel which we use on a daily basis to produce energy in power plants or even to heat up our own houses: we are talking about Natural Gas!
Fossilised natural gas can be found in deposits and it is produced from the anaerobic decomposition of organic material. It is mostly composed of methane, the smallest out of all hydrocarbon molecules. However, it can contain also ethane, propane and butane, as well as small quantities of pentane.
There are many gas fields and they are present almost all over the globe. The largest supplier is the Country of Russia, with a staggering yearly production of 624,61 Gm3 of natural gas. According to a 2010 estimate, its reserves will last at least for another 74 years. In second place, we find the Countries of Iran and Qatar, with a yearly production that ranges between 120 and 150 Gm3.
Anyway, how is natural gas extracted?
Most of the times natural gas is located in presence of a coal filed. This happens because over the years the decomposition of organic material caused the formation of layers of peat in river and torrential areas. Coal, and natural gas were generated through the fossilization of the peat layers .
Before starting with the extraction, it is necessary to carry out inspections on the territory in order to: determine the size of the field, the amount of gas present and the feasibility of the process of extraction. Geologists and geophysicists carry out tests on the reservoir site to digitally recreate the subsoil in 3D using a technique called Seismic Reflection: a sort of scan of the soil. This technique consists of firing seismic waves which, reflecting on the underlying clayey layers, are able to graphically reproduce the subsoil, highlighting potential natural gas deposits. After this initial procedure, we continue by drilling an exploration well, to make sure that the gas in present in this area. Subsequently, other types of wells are drilled, called delimitation wells. These have the function to delimit, both vertically and horizontally, the effective extent of the gas field, in order to have a precise assessment of the amount of gas. This is to ensure a fair economic return to the company that invests in a particular field.
Once the quantity of gas that the field contains have been verified, we move on to the next step, which consists in drawing up a Development Plan. The development plan will decide: how many extraction wells have to be drilled on the site, in which position, with which trajectory, the type of well (vertical, horizontal or deviated), as well as the position and number of structures necessary for the management and transport of the extracted gas
The type of the structure built to extract the gas can vary depending on the location of the field: hen the reservoir is close enough to the earth’s surface, the construction of the site and the gas extraction are easier. However, sometimes the deposit may be located under the seabed. In this case, the preparation of the site is more complex. It is necessary to build a platform in the middle of the sea, an ‘Off-shore’ platform, from which all drilling and extraction operations can be managed.
Whether on land or at sea, the drilling procedure is very similar; let’s now examine the structures and steps necessary for the extraction of natural gas.
To drill the soil, we use a special tool which resembles a rotary chisel. This chisel is composed of 3 conical heads made out of a very hard material, able to crush and shatter the soil. The chisel is attached to some 12-15 meters long rods, which are inserted as the excavation progresses. This machine is held together by a hook with steel wires connected to a system of pulleys that enables the drilling device to raise and lower. To give energy to all the instrumentation, we use an engine connected to a winch. The engine will also make the Rotary Table to start rotating and therefore, to drill . The rods brought down through the drilling are hollow and inside them flows a special mud that, in addition to lubricating the chisel, brings up the debris left by the crushing process. The excavation mud is brought to the surface through the pipes and is released into a tank where it is filtered and then separated from the debris. The mud is then re-introduced into the rig. Specifically to avoid landslides that could damage the tools , as the drill digs, the walls of the well are lined with steel pipes and cemented to the ground. Furthermore, the head of the drill is replaced with smaller and smaller ones as the excavations proceed; it starts from a 70 centimeters diameter of up to a diameter of about 10 centimeters, and the wells can reach a depth between 2 and 6 kilometers. At those depths the pressure is very high, which is why a special valve called ‘Wellhead’, or, more commonly, ‘the Christmas Tree’ is used. This equipment is a set of valves that control the pressure exerted by the gas rising to the surface. For greater safety, a Safety Valve is also installed on the so-called ‘Production Pipe’ at a depth of about 100 meters, in case the wellhead valve fails.
Once the digging phase is complete, the drill is removed and the extraction of natural gas from its field can begin.
The gas, brought to the surface by a system of pipes, is conducted into treatment tanks in order to be prepared for diffusion on the several predetermined points. In nature, gas is composed mainly of methane and it is an odourless substance. Thus, to ensure that it is perceived when there is a leak, peculiar substances are added to give it a strongly unpleasant odour. In some industrial plants, odourless natural gas is used because there are sensors that identify leaks of dangerous substances.
Once the treatment process is finished, the gas can be sorted into the various established areas. So called ‘Gas pipelines’ are used to distribute the product in houses, factories but also in power plants for the production of electricity.
Similarly to oil, gas is a limited fossil fuel. Actually, the reserves on the planet can still be exploited for many years, but fuel consumption has increased dramatically. This is why in recent years new alternative techniques have been developed to be able to produce natural gas, such as the production of ‘biogas’, which is obtained directly from the decomposition of organic waste, or with the extraction of methane from manure produced by animal farms. The technology to produce biogas exploits the formation of bacteria inside special fermenters, in this way urban organic waste, manure and agricultural waste can be transformed into gas. For instance, 5,500 cubic meters of biogas can be obtained from a landfill of 1,000,000 cubic meters. In a world where the consumption of fossil fuels is undergoing an exponential growth, can these new production represent a solution to a more sustainable society?
To drill the soil, we use a special tool which resembles a rotary chisel. This chisel is composed of 3 conical heads made out of a very hard material, able to crush and shatter the soil. The chisel is attached to some 12-15 meters long rods, which are inserted as the excavation progresses. This machine is held together by a hook with steel wires connected to a system of pulleys that enables the drilling device to raise and lower. To give energy to all the instrumentation, we use an engine connected to a winch. The engine will also make the Rotary Table to start rotating and therefore, to drill . The rods brought down through the drilling are hollow and inside them flows a special mud that, in addition to lubricating the chisel, brings up the debris left by the crushing process. The excavation mud is brought to the surface through the pipes and is released into a tank where it is filtered and then separated from the debris. The mud is then re-introduced into the rig. Specifically to avoid landslides that could damage the tools , as the drill digs, the walls of the well are lined with steel pipes and cemented to the ground. Furthermore, the head of the drill is replaced with smaller and smaller ones as the excavations proceed; it starts from a 70 centimeters diameter of up to a diameter of about 10 centimeters, and the wells can reach a depth between 2 and 6 kilometers. At those depths the pressure is very high, which is why a special valve called ‘Wellhead’, or, more commonly, ‘the Christmas Tree’ is used. This equipment is a set of valves that control the pressure exerted by the gas rising to the surface. For greater safety, a Safety Valve is also installed on the so-called ‘Production Pipe’ at a depth of about 100 meters, in case the wellhead valve fails.
Once the digging phase is complete, the drill is removed and the extraction of natural gas from its field can begin.
The gas, brought to the surface by a system of pipes, is conducted into treatment tanks in order to be prepared for diffusion on the several predetermined points. In nature, gas is composed mainly of methane and it is an odourless substance. Thus, to ensure that it is perceived when there is a leak, peculiar substances are added to give it a strongly unpleasant odour. In some industrial plants, odourless natural gas is used because there are sensors that identify leaks of dangerous substances.
Once the treatment process is finished, the gas can be sorted into the various established areas. So called ‘Gas pipelines’ are used to distribute the product in houses, factories but also in power plants for the production of electricity.
Similarly to oil, gas is a limited fossil fuel. Actually, the reserves on the planet can still be exploited for many years, but fuel consumption has increased dramatically. This is why in recent years new alternative techniques have been developed to be able to produce natural gas, such as the production of ‘biogas’, which is obtained directly from the decomposition of organic waste, or with the extraction of methane from manure produced by animal farms. The technology to produce biogas exploits the formation of bacteria inside special fermenters, in this way urban organic waste, manure and agricultural waste can be transformed into gas. For instance, 5,500 cubic meters of biogas can be obtained from a landfill of 1,000,000 cubic meters. In a world where the consumption of fossil fuels is undergoing an exponential growth, can these new production represent a solution to a more sustainable society?