Have you ever wondered where the petrol we use to run our vehicles or the gas we use for cooking originated from?. To decrypt the science behind the formation of petroleum we need to go way back in time probably as far back as 500 million years.
Plants and animals died millions of years and were buried on the sea floor,bacterial decomposition could not be completed on these dead matters due to the deficiency of oxygen on the sea bed. These partially decomposed remains continued to pile on top one another on the ocean floor and over the course of thousands of years got covered by layers of sand silt and mud .The huge weight of these sediments pressing down on the layer of partially decomposed remains compresses it into a thinner layer and finally as the depth of this overlying sediments reached thousands of feet, the immense pressure and temperature converts these massive organic deposits into oil.
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On Further increase in temperature the oil formed can be converted to natural gas.
As these mud and silt layers become heavier the forces applied causes the bottom layers above the crude oil to turn into shale- a fine grain sedimentary rock consisting of consolidated clay and mud. The oil is forced from its original location migrating upwards through the cracks and fissures in the shale formation until it reaches an impermeable rock which traps it in position until it is discovered and extracted.
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Petroleum drilled from onshore location
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Petroleum drilled from onshore location
How does this crude oil get to us at the surface?
In some geological areas the presence of rocks with cracks and fissures allows oil to actually seep up to the surface in small pond. However most oil are usually trapped underground in reservoirs (a subsurface porous and permeable rock which oil/or gas accumulates).
Petroleum formed can then be extracted by Drilling a long hole down into the earth with an oil rig. A steel pipe called casing is placed in the hole to ensure it doesn't cave in. When the target zone where our oil and gas is located is reached, the steel pipe is perforated to allow oil/gas into the drilled hole. A hollow pipe called tubing is inserted into the hole and the oil and gas is produced to the surface. Once crude oil is produced it is basically useless and need to be refined. At the surface the produced oil and gas are transported to refineries, natural gas compressor stations or oil export terminal. On getting to the refinery, crude oil is transformed and refined into more useful products such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, liquefied petroleum gas, jet fuel etc.
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