The fact about Petroleum

The facts about Petroleum

How was petroleum formed?

Just how petroleum was formed is still something of a mystery. Petroleum – both liquid oil and natural gas – does not contain any obvious clues that tell us about its origins. In contrast, we can follow the development of coal because we can find traces of prehistoric plant life in coal fragments at all stages of their formation.

All petroleum products are “complete” products and each one is fully developed in the earth and different from all the others. Some petroleum is thick and waxy and it could be used as axle grease without any changes. But some petroleum is so light that it could be used to fuel a diesel engine.

Some scientists, known as petroleum geologists, have developed a theory about the formation of this important energy source. The theory states that petroleum was formed from decayed organic material, both animal and vegetable, that lived close by – or within - the ocean. The dead material was built up on the ocean floor. Then certain chemical al­teration processes turned the dead material (debris) into fatty and waxy substances.

Over time, the buried substances - dead marine animals and plants – became petroleum. It is estimated that this process (the conversion of decayed organic material into petroleum) took up to 10 million years. The creation of petroleum occurred sometime between 200 and 400 million years ago. Now. The question we ask, if the creation of Petroleum it takes us to 400 million years, then how old exactly our country? No one could tell the exact age of our beloved island existed.

Another, but less-accepted theory, is that volatile fluids have “cooked out” from the earth’s rock mantle when the planet was forming. The fluids work their way to the upper layers of the earth's crust. Petroleum is formed in rocks that are fine-grained and soft. There are great forces of water and pressure acting on these porous rocks. This pressure eventually forced the petroleum from the pores and cracks of the rocks.

The petroleum was gradually “squeezed” into the water’s depths and it continued to rise until it reached a barrier known as a “seal”. The petroleum then moved along the barrier until it reached the highest point, known as a “trap”. Then it could go no further. It began to accumulate as more and more was squeezed out of the porous rock. This movement or “migration”, so long and so slow, often means that petroleum is discovered far away from the place where it was formed, and in a great variety of rocks. Often, it is found in large amounts in places where rocks have been forced by earth movements into the form of a dome. Petroleum rises into the dome and it is trapped there. The rocks that capture the petroleum are called reservoir rocks.

A typical petroleum deposit is made up of three layers:
1. There is a zone where the pores of the rocks are filled with natural gas.

2. Underneath the gas is a zone where the rocks have their inter­stices (or pores) full of oil. This oil also contains dissolved gas, as the gas is under great pressure (Similar to bottled gas, propane and butane gases which are liquids through pressure.)

3.Beneath the oil is water.

Dear readers, Now the next step is that knowing who finds the Petroleum, and where? the following passage is gonna be very interesting one, as it is essential what we should know for the sake of the general knowledge.

Who finds petroleum and where?
Finding petroleum was once a job for prospectors who dug wells in places that they thought would be suitable - perhaps a line of hills or a swamp. So they drilled a hole there and it was known as a “wild-cat” well. But the demand for petroleum became too great to rely on guesswork. Wild­cat prospectors had to give way to specialist scientists. These scientists are geologists and geophysicists.
Geologists study rocks and soils in the layers of the earth’s crust. Many geologists are specialists. Some are interested in sedimentary rocks. These are called sedimen­tologists. Others study fossils. They are palaeontologists.

Others specialise in the chemistry of rocks and the fluids they con­tain. These are geochemists. They work closely with geophysicists in the search for petroleum. Geophysicists study and measure the physical phenomena of the earth. They measure temperature, magnetism, earth movements, water flow, assess earthquakes. Their measurements are used for three purposes:
1. First, to improve our knowledge and understanding of the earth (what it is and what makes it tick).

2. Second, to find out what is the nature of the earth for the construction of tunnels, buildings, power stations and other structures.

3. And third, to explore the earth for petroleum, natural gas and minerals, and to establish whether these are suitable for commercial exploitation.

To make their measurements, they “read” gravity, electricity, light, shock waves, sound, heat and radioactivity. They put their instru­ments on the surface, underground, in water, in the air - or all four. They also produce vibrations in the earth using vibrat­ing machines or compressed air “guns” in the ocean. Recordings of the transmitted and reflected vibrations will “tell” them what sort of rocks there are. These are called seismic surveys. (“Seis­mology” is the study of earthquakes.

The Geophysicists can tell petroleum explorers where these large areas of sedimentary rocks (sedimentary basins) are located. They do this by measuring the gravitational force and the earth’s magnetic field at the earth’s sur­face. Areas of lower magnetic field strength and lower gravitational force are areas underlain by sedimentary rocks. There are a number of Australian sedimentary basins.

There are two seismic methods to detect sedimentary rocks: reflection and refraction. In both methods, shock waves pass through the rock structure and are recorded on a device called a geophone. When their underground maps are ready, geophysicists hand them over to petroleum engineers, because the only sure way to tell if the petroleum is actually there is to drill. Tests wells are drilled, to bring up samples of rock. These are studied for evidence of petroleum.

Petroleum geophysicists look for sediments. But they know that petroleum often has migrated from the place where it was formed. So they look for the non-porous rocks that have “trapped” petroleum. When oil exploration wells are drilled, a range of “down hole” measurement tools can detect more information from the well, such as rock density, radioactivity, magnetic strength and porosity. Geophysicists can “read” the differences because their instru­ments “behave” in different ways for each. Similarly, differences be­tween coal, water and petroleum can be detected. So geophysicists look for “con­trasts” and these differences tell them about ore bodies and reefs; or ancient earth movements; or strange rocks that earthquakes have shoved into other rocks.

If petroleum is there, how much? Can it be recovered? How much can be recovered? If oil or gas is produced from a well, its pressure and flow rates are accurately measured. Most of the wells that are sunk are dry. Either no petroleum or gas is found, or the amount is so small it is not worth getting out. The search never stops!