Occurrence of Petroleum.

HISTORY and Development of Petroleum

Petroleum has been known throughout historical time. It was used in mortar, for coating walls and boat hulls, and as a fire weapon in defensive warfare. Native Americans used it in magic and medicine and in making paints. Pioneers bought it from the Native Americans for medicinal use and called it Seneca oil and Genesee oil. In Europe it was scooped from streams or holes in the ground, and in the early 19th cent. small quantities were made from shale. In 1815 several streets in Prague were lighted with petroleum lamps.

The modern petroleum industry began in 1859, when the American oil pioneer E. L.Drake drilled a producing well on Oil Creek in Pennsylvania at a place that later became Titusville. Many wells were drilled in the region. Kerosene was the chief finished product, and kerosene lamps soon replaced whale oil lamps and candles in general use. Little use other than as lamp fuel was made of petroleum until the development of the gasoline engine and its application to automobiles, trucks, tractors, and airplanes. Today the world is heavily dependent on petroleum for motive power, lubrication, fuel, dyes, drugs, and many synthetics. The widespread use of petroleum has created serious environmental problems. The great quantities that are burned as fuels generate most of the air pollution in industrialized countries, and oil spilled from tankers and offshore wells has polluted oceans and coastlines.

MODE OF OCCURRENCE

During the past 600 million years incompletely decayed plant and animal remains have become buried under thick layers of rock. It is believed that petroleum consists of the remains of these organisms but it is the small microscopic plankton organism remains that are largely responsible for the relatively high organic carbon content of fine-grained sediments like the Chattanooga shale which are the principle source rocks for petroleum. Among the leading producers of petroleum are Saudi Arabia, Russia, the United States (chiefly Texas, North Dakota, Alaska, and California), China, Iran, Canada, the United Arab Emirates, Mexico, Brazil, Kuwait, Iraq, Nigeria, Venezuela, and Norway. The largest proven reserves are in the Middle East.

Geographic location 

Geographic location refers to a position on the Earth. Your absolute geographic location is defined by two coordinates, longitude and latitude. These two coordinates can be used to give specific locations independent of an outside reference point.

What is longitude and latitude?

Latitude is the measure, in degrees, of the distance of a location from the equator, which divides the Earth into Northern and Southern Hemispheres. Longitude is the measure, in degrees, of a location from the prime meridian, the starting point from which the time zones are calculated.

What divides Earth into the Northern and Southern Hemispheres?

The Earth's Northern and Southern Hemispheres are divided by the equator, which is an imaginary line located at 0 degrees latitude. The Northern Hemisphere consists of most of Asia, northern South America, Europe, North America and two-thirds of Africa's landmass. The Earth's Southern Hemisphere is comprised of Antarctica, one-third of Africa, Australia, a small number of Asian islands and much of South America.

Where is the equator located?

The equator is an imaginary line located at 0 degrees latitude, stretching around the middle of the Earth. It divides the planet into the Northern and Southern hemispheres. Daytime at the equator always lasts 12 hours, with night also lasting 12 hours.

Location (geography)

The terms location and place in geography are used to identify a point or an area on the Earth's surface or elsewhere. The term location generally implies a higher degree of certainty than place, which often indicates an entity with an ambiguous boundary, relying more on human or social attributes of place identity and sense of place than on geometry. 

Types of location and place

Relative location

A relative location, or situation, is described as a displacement from another site. An example is "3 miles northwest of Seattle".

Locality

A locality, settlement, or populated place is likely to have a well-defined name but a boundary which is not well defined in varies by context. London, for instance, has a legal boundary, but this is unlikely to completely match with general usage. An area within a town, such as Covent Garden in London, also almost always has some ambiguity as to its extent.

Absolute location

An absolute location is designated using a specific pairing of latitude and longitude in a Cartesian coordinate grid — for example, a Spherical coordinate system or an ellipsoid-based system such as the World Geodetic System — or similar methods

GEOLOGICAL AGE OF RESERVIOR ROCK

A reservoir rock is a place that oil migrates to and is held underground. A sandstone has plenty of room inside itself to trap oil. It is for this reason that sandstones are the most common reservoir rocks. Limestone and dolostones, some of which are the skeletal remains of ancient coral reefs, are other examples of reservoir rocks.

A fundamental property of a reservoir rock is its porosity. However, for it to be an effective reservoir rock, THE fundamental property is permeability. Both porosity and permeability are geometric properties of a rock and both are the result of its lithologic (composition) character. The physical composition of a rock and the textural properties (geometric properties such as the sizes and shapes of the constituent grains, the manner of their packing) are what is important when discussing reservoir rocks and not so much the age of the rock.

Petroleum Reservoir 

A petroleum reservoir or oil and gas reservoir is a subsurface pool of hydrocarbons contained in porous or fractured rock formations. Petroleum reservoirs are broadly classified as conventional and unconventional reservoirs.

 conventional and unconventional reservoirs.

 In case of conventional reservoirs, the naturally occurring hydrocarbons, such as crude oil or natural gas, are trapped by overlying rock formations with lower permeability. While in unconventional reservoirs the rocks have high porosity and low permeability which keeps the hydrocarbons trapped in place, therefore not requiring a cap rock. Reservoirs are found using hydrocarbon exploration methods.

Formation

Crude oil found in all oil reservoirs formed in the Earth's crust from the remains of once-living things. Crude oil is properly known as petroleum, and is used as fossil fuel. Evidence indicates that millions of years of heat and pressure changed the remains of microscopic plant and animal into oil and natural gas.

Roy Nurmi, an interpretation adviser for Schlumberger, described the process as follows: "Plankton and algae, proteins and the life that's floating in the sea, as it dies, falls to the bottom, and these organisms are going to be the source of our oil and gas. When they're buried with the accumulating sediment and reach an adequate temperature, something above 50 to 70 °C they start to cook. This transformation, this change, changes them into the liquid hydrocarbons that move and migrate, will become our oil and gas reservoir.

In addition to the aquatic environment, which is usually a sea, but might also be a river, lake, coral reef or algal maT, the formation of an oil or gas reservoir also requires a sedimentary basin  that passes through four steps: deep burial under sand and mud, pressure cooking , hydrocarbon migration from the source to the reservoir rock, and trapping by impermeable rock. Timing is also an important consideration; it is suggested that the Ohio River Valley could have had as much oil as the Middle East at one time, but that it escaped due to a lack of traps. The North Sea , on the other hand, endured millions of years of sea level changes that successfully resulted in the formation of more than 150 oilfields .

Although the process is generally the same, various environmental factors lead to the creation of a wide variety of reservoirs. Reservoirs exist anywhere from the land surface to 30,000 ft (9,000 m) below the surface and are a variety of shapes, sizes and ages.