Read the text and do the exercises.

OIL FORMATION

Oil, natural gas and petroleumhave been foremost on people’s minds for the past years. Nations and the world are run by oil. It fuels our cars, our homes and provides us with electricity. It is used in the making of plastics and cosmetics. Oil is also prevalent in our lives, but most people don’t know where the oil we use comes from.

Terms and Vocabulary

сrude oil сырая нефть

мixture смесь

hydrocarbons углеводороды

separation разделение, разложение на части

refining очистка, перегонка (нефти)

volatile летучий, быстро испаряющийся

viscous густой, вязкий

residue остаток

reservoir rock порода-коллектор

source rock нефтематеринская порода

porous пористый

porosity пористость

permeable (impermeable) проницаемый (непроницаемый)

permeability проницаемость

cap rock покрывающая порода, покрышка

залежи

sulphur сера

nitrogen азот

oxygen кислород

feedstock исходное сырье

split up (v) разделять

be arranged быть систематизированным,

упорядоченным

tarry смолистый

alter (v) изменить

sink (v) погружаться

decay гнить, перегнивать

fine-grained мелкозернистый

exert (v) оказывать давление

trap (n,v) ловушка; заключать в ловушку

property свойство

shale сланец

accumulate (v) накапливать; накоплять

limestone известняк

sandstone песчаник

Read the text and do the exercises.

1. Crude oilis a complex mixture of hydrocarbonswith minor proportions of other chemicals such as compounds of sulphur, nitrogenand oxygen. To use the different parts of the mixture they must be separated from each other. This separationis called refining.

2.Crude oils from different parts of the world, or even from different depthsin the same oilfield, contain different mixtures of hydrocarbons and other compounds. This is why they vary from light colored volatile liquidsto thick, dark oils – so viscousthat they are difficult to pump from the ground.

3.Hydrocarbons vary in structure depending on the number of carbon atoms and the way in which the hydrogen atoms combine with them. Hydrocarbons can be arrangedas straight chains, branched chains or closed rings. There are two main chemical families of hydrocarbons – the alkanes and the alkenes.

4.As the structure of hydrocarbons varies so much, thousands of synthetic products can be manufactured with many different properties. Hydrocarbons with small molecules make good fuels. Methane (CH4) has the smallest molecules, and is a gas, used for cooking and heating and generating electricity. Gasoline, diesel, aviation fuel and fuel oil are all liquid fuels.

5.Hydrocarbon molecules can be split upinto smaller ones or built up into bigger ones, or alteredin shape, or modified by adding other atoms. This is why they are a very useful starting point (called a chemical feedstock) for making other materials. Even the thick black tarry residueleft after distillation is useful. It is called bitumen and is used in tarmac for road surfacing and for roofing.

6.Oil is formed from the remains of tiny plants and animals (plankton) that died in ancient seas between 10 and 600 million years ago. After the organisms died, they sankinto the sand and mud at the bottom of the sea. Over the years, the organisms decayedin the sedimentary layers. In these layers there was little or no oxygen present. So microorganisms broke the remains into carbon-rich compounds that formed organic layers. The organic material mixed with the sediments, forming fine-grained shale, or source rock.As new sedimentary layers were deposited, they exertedintense pressure and heat on the source rock. The heat and pressure distilled the organic material into crude oil and natural gas. The oil flowed from the source rock and accumulatedin thicker, more porous limestoneor sandstone, called reservoir rock. Movements in the Earth trappedthe oil and natural gas in the reservoir rocks between layers of impermeable rock, or cap rock, such as granite or marble.