where does oil come from?

Answers to where does oil come from

Oil was formed from the remains of animals and plants that lived millions of years ago in a marine (water) environment before the dinosaurs. Over the years, the remains were covered by layers of mud. Heat and pressure from these layers helped the remains turn into what we today call crude oil. The word "petroleum" means "rock oil" or "oil from the earth."

Crude oil is a smelly, yellow-to-black liquid and is usually found in underground areas called reservoirs.  Scientists and engineers explore a chosen area by studying rock samples from the earth.  Measurements are taken, and, if the site seems promising, drilling begins.  Above the hole, a structure called a 'derrick' is built to house the tools and pipes going into the well.  When finished, the drilled well will bring a steady flow of oil to the surface.

The world's top five crude oil-producing countries are:
       * Saudi Arabia
       * Russia
       * United States
       * Iran
       * China

Over one-fourth of the crude oil produced in the United States is produced offshore in the Gulf of Mexico. The top crude oil-producing states are:
       * Texas
       * Alaska
       * California
       * Louisiana
       * New Mexico

Historical View
Have you ever heard the term fossil fuel? It means a source of energy that comes from once-living things. You know about such fossils as dinosaur bones. Those fossils are bones that over a long period of time turned to stone. Just as those bones turned to stone, other bones turned to oil. Oil is made of bones and tree trunks and shells and all sorts of other parts of organisms that lived thousands and even millions of years ago.

When living things die, they are broken down and covered over by dust, soil, or sand. As they are covered over by other layers of once-living things and by more layers of soil, sand, and rock, they get buried deeper and deeper below Earth’s surface. These “sandwiches” of once-living things, sand, and soil are eventually subjected to very high pressure and to very high temperature. When the pressure is great enough, the sand and soil change into rock. And at just the right temperature, the once-living things change into a liquid called oil and a gas called natural gas.

After oil and gas form, other layers of rock continue to press down from above, causing still more pressure. This pressure causes the rock to go even deeper into the Earth. But this pressure on the oil and gas is like pushing a balloon under water; it just tends to pop back up again. The oil and gas move upward through cracks and holes in the rock. One kind of rock, called reservoir rock, contains many small holes, or pores. Oil and gas are often found in this porous rock. Finally, the oil and gas are stopped from moving upward by other, nonporous layers of rock. Then the oil and gas pool in a trap, where the oil may remain until it’s discovered and the rock is drilled to extract it. You may wonder how people find oil. In the past, oil was often found accidentally. There were many areas where oil traps lay close to the surface. In these areas, if someone dug a deep hole in the ground, the digger might reach the oil trap. Once a hole was made into the trap, gas and oil would shoot out and up into the air. Many oil wells in Texas were accidentally discovered in this way.

Digging Deeper
In the leading theory, dead organic material accumulates on the bottom of oceans, riverbeds or swamps, mixing with mud and sand. Over time, more sediment piles on top and the resulting heat and pressure transforms the organic layer into a dark and waxy substance known as kerogen.

Left alone, the kerogen molecules eventually crack, breaking up into shorter and lighter molecules composed almost solely of carbon and hydrogen atoms. Depending on how liquid or gaseous this mixture is, it will turn into either petroleum or natural gas.

So how long does this process take?
Scientists aren't really sure, but they figure it's probably on the order of hundreds of thousands of years.

"It's certainly not an instantaneous process," Thomas told LiveScience. "The rate at which petroleum is forming is not going to be the solution to our petroleum supplies."

The United States' latest reminder of its petroleum dependency occurred when hurricanes Katrina and Rita struck the Gulf of Mexico, where the majority of the country's oil platforms and refineries are located. Many analysts predicted gas prices would surge to $4 and $5 per gallon, but the fears turned out to be overblown. Many of the structures suffered only glancing blows and were operating again soon afterwards.

Yet Another View
There is general agreement in mainstream science that petroleum originated when organic matter in ancient muds and clays accumulated in subsiding geological basins. This sediment was heated over a period of millions of years as geological processes brought the material deeper underground. The end product depends on just how deep the organic-rich sediments were carried. At 150 - 200 C, natural gas is the end produce. At 60 - 150 C, oils are produced, and leach out of the rocks to form pockets that get trapped between impermeable layers of shale.

The geologic period when petroleum deposits can form depends on a balance between sufficient sources of organic material ( trees, plants etc with waxy 'hydrocarbon coatings') and the occurrence of the proper geologic subsidence and trapping processes. Deposits found in Precambrian rocks are rare, as are deposits in the much more recent Pleistocene 'rocks'. However, tar deposits are found in the latter rocks such as the famous 'La Brea Tar Pits' in southern California. It takes several million years for the petroleum products such as oil to migrate out of their parent rocks into the appropriate 'reservoir' rocks where they get trapped and accumulated into sub-surface pools. Radioactive dating of the rocks in which oil deposits occur span the range from the Cambrian Era to the Cretaceous Era between 65 million and 500 million years ago.

Creationists propose that these deposits were laid down by the Great Biblical Flood some few thousand years ago in 2350 B.C, when the organic deposits ( Flood victims) were entombed in the Earth. Their conversion into oil and gas deposits then took a few thousand years to the present time. So, everytime you fill up at the gas pump you are pouring liquified dead humans and ancient creatures into your car.

What is the chief evidence that disputes the Creationist proposal? The migration of petroleum from their strata of origin into surrounding rocks takes a long time, measured in millions of years, not centuries. This is based on the physics of fluid flow through semi-permeable material under a pressure gradient. There is nothing speculative about this mechanism, anymore than there is controversy over how water flows through a garden hose. There is also the problem of the time scale for conversion 'or cracking' of organic matter into oil and gas derivatives under the rather gentle temperature and pressure conditions found in nature. Again this is a matter of organic chemistry, not speculation, and the time scales are again measured in millions of years not days or centuries.

Disclaimer - Answers to the questions are researched using various sources and are meant to increase the knowledge of our visitors. We cannot gurantee the accuracy of answers to questions.

Questions & Answers Page 2
Questions & Answers Page 1
Get Savio DSilva's Books for Free