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widely, but below is a chart outlining the typical makeup of natural gas before it is refined.

Typical Composition of Natural Gas
Methane	CH4	70-90%
Ethane	C2H6
Propane	C3H8	0-20%
Butane	C4H10
Carbon Dioxide	CO2	0-8%
Oxygen	O2	0-0.2%
Nitrogen	N2	0-5%
Hydrogen sulphide	H2S	0-5%
Rare gases	A, He, Ne, Xe	trace

In its purest form, such as the natural gas that is delivered to your home, it is almost pure methane. Methane is a molecule made up of one carbon atom and four hydrogen atoms, and is referred to as CH4.

A Methane molecule, CH4

Natural gas is considered ‘dry’ when it is almost pure methane, having had most of the other commonly associated hydrocarbons removed. When other hydrocarbons are present, the natural gas is ‘wet’.

Natural gas is a fossil fuel. Like oil and coal, this means that it is, essentially, the remains of plants and animals and microorganisms that lived millions and millions of years ago. But how do these once living organisms become an inanimate mixture of gases?

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There are many different theories as to the origins of fossil fuels. The most widely accepted theory says that fossil fuels are formed when organic matter (such as the remains of a plant or animal) is compressed under the earth, at very high pressure for a very long time. This is referred to as thermogenic methane. Similar to the formation of oil, thermogenic methane is formed from organic particles that are covered in mud and other sediment.

Over time, more and more sediment and mud and other debris are piled on top of the organic matter. This sediment and debris puts a great deal of pressure on the organic matter, which compresses it. This compression, combined with high temperatures found deep underneath the earth, break down the carbon bonds in the organic matter. As one gets deeper and deeper under the earths crust, the temperature gets higher and higher. At low temperatures (shallower deposits), more oil is produced relative to natural gas. At higher temperatures, however, more natural gas is created, as opposed to oil. That is why natural gas is usually associated with oil in deposits that are 1 to 2 miles below the earth’s crust. Deeper deposits, very far underground, usually contain primarily natural gas, and in many cases, pure methane.

Natural gas can also be formed through the transformation of organic matter by tiny microorganisms. This type of methane is referred to as biogenicmethane.Methanogens,tinymethaneproducingmicroorganisms, chemically break down organic matter to produce methane. These microorganisms are commonly found in areas near the surface of the earth that are void of oxygen. These microorganisms also live in the intestines of most animals, including humans. Formation of methane in this manner usually takes place close to the surface of the earth, and the methane produced is usually lost into the atmosphere. In certain circumstances, however, this methane can be trapped underground, recoverable as natural gas. An example of biogenic methane is landfill gas. Waste-containing landfills produce a relatively large amount of natural gas, from the decomposition of the waste materials that they contain. New technologies are allowing this gas to be harvested and used to add to the supply of natural gas.

A third way in which methane (and natural gas) may be formed is through abiogenic processes. Extremely deep under the earth’s crust, there exist hydrogen-rich gases and carbon molecules. As these gases gradually rise towards the surface of the earth, they may interact with minerals that also exist underground, in the absence of oxygen. This interaction may result in a reaction, forming elements and compounds that are found in the atmosphere (including nitrogen, oxygen, carbon dioxide, argon, and water). If these gases are under very high pressure as they move towards the surface of the earth, they are likely to form methane deposits, similar to thermogenic methane.

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The use of natural gas as a primary fuel is relatively recent, as for many years gas was seen as a necessary by-product from the extraction of crude oil. From 1960, as pipelines and local gas transmission networks have been constructed, the growth in demand for natural gas has been spectacular. Now gas supplies over 30% of the world’s total energy demand . Like oil, natural gas is an important raw material for the petro-chemical industry and is used to obtain a multitude of products including ammonia, (for nitrogen fertilizers) and methanol (the basis of many plastics and other synthetic materials).

Natural gas is often found together with crude oil deposits and is formed by similar processes. It is also produced by the degradation of older carbon deposits, such as coal. As crude oil reserves are extracted, natural gas accumulates in the upper chambers of the seam and can be recovered once the extraction of crude is no longer viable. In this type of gas field, quantities of propane and butane are also recovered which are utilised for domestic and industrial use as LPG (liquid propane gas).

Natural gas is also found in dry seams, not in association with oil, as in the extensive Russian and NIS region gas fields. Detection and extraction techniques are similar to those for oil. Wells are typically 5000 metres deep, or more, and are lined to reduce contamination. The extracted gas is cleaned by absorption or cryogenic processes to remove heavy hydrocarbons and other impurities like sulphur.

Natural gas often has to be transported great distances from the gas fields to the demand centres. Two methods are used:

by ship, carried as liquid methane at around 160°C below zero

pumped through large diameter pipelines.

Pipeline technology has played a key role in the development of

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markets for natural gas. Gas has to be transported vast distances, often across continents, and users require stability in pressure and continuous supply. Large diameter pipes (up to around 4m) are used to minimise pressure, yet the cost of the pipe increases quickly with pipe size and intermediate pumping stations are required.

Natural gas can be measured in a number of different ways. As a gas, it can be measured by the volume it takes up at normal temperatures and pressures, commonly expressed in cubic feet. Production and distribution companies commonly measure natural gas in thousands of cubic feet (Mcf), millions of cubic feet (MMcf), or trillions of cubic feet (Tcf). While measuring by volume is useful, natural gas can also be measured as a source of energy. Like other forms of energy, natural gas is commonly measured and expressed in British thermal units (Btu). One Btu is the amount of natural gas that will produce enough energy to heat one pound of water by one degree at normal pressure. To give an idea, one cubic foot of natural gas contains about 1,027 Btus. When natural gas is delivered to a residence, it is measured by the gas utility in ‘therms’ for billing purposes. A therm is equivalent to 100,000 Btu’s, or just over 97 cubic feet, of natural gas.

Nowadays, gas pipelines even cross straits joining continents, like that of Gibraltar which ensures the supply of gas from Algeria to Europe. Major pipelines bring gas from Russia and Scandinavia into Western and Central Europe and others supply the USA and Central America from the Canadian fields. A major pipeline project is currently underway in Latin America to bring gas from the Andes in the West of the continent, across the Amazon Basin to supply the industrial regions of Brazil in the East.

The large liquid gas distribution centres are in the Mediterranean (Algeria and Libya), the Pacific Rim (Indonesia, Brunei, Malaysia and Alaska) and NIS countries. The Russian and other NIS gas fields produce around half of the world’s present gas demand. Other major fields are in the Middle East and North Sea.

A Christmas tree is a set of valves, pipes, and fittings used to control the flow of oil and gas as it leaves a well and enters a pipeline.

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IV. Knowing Ins and Outs

Read the question and three possible answers, translate them into Russian. Decide which one is the safest choice. Explain your decision.

Living Dangerously?

1. Someone spilled paint in your kitchen and it splashed on your natural gas range. What do you do?

Simple! Just grab a rag and clean it up with paint thinner.

Wipe up the splash with clean, dry rags. If you must use a flammable solvent, turn off the gas to your stove, extinguishing the pilot light. Clean off any residue, and ventilate fumes before relighting the pilot.

Use a very deluted solution of solvent to clean the paint splash.

2.You come home from work to find a strong natural gas odor in your home. What do you do?

Call the utility immediately!

Get a flashlight and look for the leak.

Get everyone out of the house immediately. Go to a nearby phone and call the utility.

3.Your electricity is out and your house is very cold. What do you do to keep warm?

Bundle up or stay with a friend who still has power until your power is restored.

Light your gas oven and huddle around the open oven door.

Bring your camp stove into the kitchen and fire it up.

4.You collect magazines and are looking for an out-of-the-way place to store them. What do you do?

Store the magazines in that clean, dry spot right next to your furnace.

Store the magazines next to the water heater but off the ground, so they don’t get wet if the water malfunctions.

Store magazines in the attic, away from natural gas appliances.

5.It’s the start of the heating season, and you suspect your natural gas furnace may need a tune-up. What do you do?

Call a qualified service person to check your furnace and its flue before you light your furnace.

Run your furnace for a few days to see if it’s working properly.

Check the furnace yourself. If you don’t see anything wrong, it should be fine.

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6. While digging a hole for a fence post in your backyard, you hit a natural gas pipeline and puncture it slightly. But you don’t hear any hissing sound. What do you do?

Quick! Fill in the hole and put the fence post a few inches away.

Leave the hole open and notify the utility.

Pour concrete in the hole.

7. The burner flames on your gas range top are glowing bright yellow. What do you do?

The burner of your gas range should have blue flames. Have a professional check the range immediately.

No problem. As long as the range lights, it’s fine.

Clean the burners. If the flames are still yellow, that’s the way it is supposed to be.

8.You and your family members are having headaches and fluelike symptoms that seem to coincide with spending time inside your home. What do you do?

Buy a carbone monoxide detector and see if the alarm goes off.

Get your family out of the house immediately. Seel treatment for carbon monoxide poisoning. Call your utility for an emergency inspection.

Have someone check your house in a week or two.

9.The pilot light goes out on your natural gas heater. What do you do?

Wait to light it until later when you get back from work.

Quick. Find a match and relight the pilot light as soon as you discover it’s out.

First, make sure the appliance is off, open nearby window to ventilate any buildup of gas, and wait five minutes. Then follow the manufacturer’s directions to relight the pilot.

V.Enhancing Skills in English-Russian Interpretation

Render orally the following text:

Exploration

The practice of locating natural gas and petroleum deposits has been transformed dramatically in the last 15 years with the advent of extremely advanced, ingenious technology. In the early days of the industry, the only way of locating underground petroleum and natural gas deposits was to search for surface evidence of these underground formations. Those searching for natural gas deposits were forced to scour the earth, looking for seepages of oil or gas emitted from underground

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before they had any clue that there were deposits underneath. However, because such a low proportion of petroleum and natural gas deposits actually seep to the surface, this made for a very inefficient and difficult exploration process. As the demand for fossil fuel energy has increased dramatically over the past years, so has the necessity for more accurate methods of locating these deposits.

Sources of Data

Technology has allowed for an incredible increase in the success rate of locating natural gas reservoirs. In this section, it will be outlined how geologists and geophysicists use technology, and knowledge of the properties of underground natural gas deposits, to gather data that can later be interpreted and used to make educated guesses as to where natural gas deposits exist. However, it must be remembered that the process of exploring for natural gas and petroleum deposits is rife with uncertainty and trial-and-error, simply due to the complexity of searching for something that is often thousands of feet below ground.

Geological Surveys

The exploration for natural gas typically begins with geologists examining the surface structure of the earth, and determining areas where it is geologically likely that petroleum or gas deposits might exist. It was discovered in the mid 1800’s that anticlinal slopes had a particularly increased chance of containing petroleum or gas deposits. These anticlinal slopes are areas where the earth has folded up on itself, forming the dome shape that is characteristic of a great number of reservoirs.

By surveying and mapping the surface and sub-surface characteristics of a certain area, the geologist can extrapolate which areas are most likely to contain a petroleum or natural gas reservoir. The geologist has many tools at his disposal to do so, from the outcroppings of rocks on the surface or in valleys and gorges, to the geologic information attained from the rock cuttings and samples obtained from the digging of irrigation ditches, water wells, and other oil and gas wells. This information is all combined to allow the geologist to make inferences as to the fluid content, porosity, permeability, age, and formation sequence of the rocks underneath the surface of a particular area. For example, in the picture shown, a geologist may study the outcroppings of rock to gain insight into the geology of the subsurface areas.

Once the geologist has determined an area where it is geologically possible for a natural gas or petroleum formation to exist, further tests can be performed to gain more detailed data about the potential reservoir

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area. These tests allow for the more accurate mapping of underground formations, most notably those formations that are commonly associated with natural gas and petroleum reservoirs. These tests are commonly performed by a geophysicist, one who uses technology to find and map underground rock formations.

Seismic Exploration

Arguably the biggest breakthrough in petroleum and natural gas exploration came through the use of basic seismology. Seismology refers to the study of how energy, in the form of seismic waves, moves through the Earth’s crust and interacts differently with various types of underground formations. In 1855, L. Palmiere developed the first ‹seismograph›, an instrument used to detect and record earthquakes. This device was able to pick up and record the vibrations of the earth that occur during an earthquake. However, it wasn’t until 1921 that this technology was applied to the petroleum industry and used to help locate underground oil formations.

The basic concept of seismology is quite simple. As the Earth’s crust is composed of different layers, each with its own properties, energy (in the form of seismic waves) traveling underground interacts differently with each of these layers. These seismic waves, emitted from a source, will travel through the earth, but also be reflected back towards the source by the different underground layers. It is this reflection that allows for the use of seismology in discovering the properties of underground geology. Geophysicists are able to artificially create vibrations on the surface and record how these vibrations are reflected back to the surface.

An analogy that makes intuitive sense is that of bouncing a rubber ball. A rubber ball that is dropped on concrete will bounce in a much different way than a rubber ball dropped on sand. In the same manner, seismic waves sent underground will reflect off of dense layers of rock much differently than extremely porous layers of rock, allowing the geologist to infer from seismic data exactly what layers exist underground and at what depth. While the actual use of seismology in practice is quite a bit more complicated and technical, this basic concept still holds.

Onshore Seismology

In practice, using seismology for exploring onshore areas involves artificially creating seismic waves, the reflection of which are then picked up by sensitive pieces of equipment called ‘geophones’, imbedded in the ground. The data picked up by these geophones are then transmitted to a seismic recording truck, which records the data for further interpretation

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by geophysicists and petroleum reservoir engineers. The drawing shows the basic components of a seismic crew. The source of seismic waves (in this case an underground explosion) creates vibrations which reflect off of the different layers of the earth, to be picked up by geophones on the surface and relayed to a seismic recording truck to be interpreted and logged.

Although the seismograph was originally developed to measure earthquakes, it was discovered that much the same sort of vibrations and seismic waves could be produced artificially and used to map underground geologic formations. In the early days of seismic exploration, seismic waves were created using dynamite. These carefully planned, small explosions created the requisite seismic waves, which were then picked up by the geophones, generating data to be interpreted by geophysicists, geologists, and petroleum engineers.

Recently, due to environmental concerns and improved technology, it is often no longer necessary to use explosive charges to generate the needed seismic waves. Instead, most seismic crews use non-explosive seismic technology to generate the required data. This non-explosive technology usually consists of a large heavy wheeled or tracked vehicle carrying special equipment designed to create a large impact or series of vibrations. These impacts or vibrations create seismic waves similar to those created by dynamite. In the seismic truck shown, the large piston in the middle is used to create vibrations on the surface of the earth, sending seismic waves that are used to generate useful data.

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Offshore Seismology

The same sort of process is used in offshore seismic exploration. When exploring for natural gas that may exist thousands of feet below the seabed floor, which may itself be thousands of feet below sea level, a slightly different method of seismic exploration is used. Instead of trucks and geophones, a ship is used to pick up the seismic data. Instead of geophones, offshore exploration uses hydrophones, which are designed to pick up seismic waves underwater. These hydrophones are towed behind the ship in various configurations depending on the needs of the geophysicist. Instead of using dynamite or impacts on the seabed floor, the seismic ship uses a large air gun, which releases bursts of compressed air under the water, creating seismic waves that can travel through the Earth’s crust and generate the seismic reflections that are necessary.

Magnetometers

In addition to using seismology to gather data concerning the composition of the Earth’s crust, the magnetic properties of underground formations can be measured to generate geological and geophysical data. This is accomplished through the use of magnetometers, which are devices that can measure the small differences in the Earth’s magnetic field. In the early days of magnetometers, the devices were large and bulky, and only able to survey a small area at a time. However, in 1981, NASA launched a satellite, equipped with magnetometer technology, capable of taking magnetic measurements on a continental scale. This satellite, called Magsat, allows for the study of underground rock formations and the Earth’s mantle on a larger scale, and provides clues as to tectonic plate movement and the location of deposits of petroleum, natural gas, and other valuable minerals.

Gravimeters

In addition to using variances in the Earth’s magnetic field, geophysicists can also measure and record the difference in the Earth’s gravitational field to gain a better understanding of what is underground. Different underground formations and rock types all have a slightly different effect on the gravitational field that surrounds the Earth. By measuring these minute differences with very sensitive equipment, geophysicists are able analyze underground formations and have a clearer insight into exactly what types of formations lie below ground; and, whether or not they have the potential for containing hydrocarbons like natural gas.

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