Understanding Oil and Gas

Introduction
History of oil starts from more than 4000 years ago, when oil was used for constructing walls in Babylon. It was also used as medicine for human injuries. Modern history of oil starts when oil wells were drilled in North America in 1858. The commercial use of oil starts here and it had its peak in 1940’s till now. As usage of oil increases day by day more than the resources available, world started looking at crude oil as “Black Gold”. They started looking for the alternative way to produce oil in artificial manner. For this kind of production of oil, the search of answer for the question “how oil origins naturally?” will be of great use.



Origin of Oil
Origin of oil is not yet clear. There are many theories out of which two are biogenic and Abiogenic theory discussing origin of oil. According to biogenic theory crude oil is formed from the buried organic materials. These organic materials got mixed up with mud and undergo high pressure and temperature under the earth. First forms a waxy material known as “Kerogen” and after experiencing more heat, it gets changed to liquid and gaseous phase and this process is called “Cyrogenic”. Because of the oil weight compared to rock, it tries to escape upwards through the adjacent holes, pours and cracks. When they find no place to escape they get trapped and form “Oil Pool”. This is the explanation about origin of oil by biogenic theory which has become traditional over a period of time.

But in 1950 scientists from Russia and Ukraine came up with the new theory called Abiogenic theory, which is totally against biogenic theory. According to Abiogenic theory the petroleum deposits are formed deep in the earths crust and form inorganic materials. These scientists argued that the high pressure required for the formation of oil, is found in the deep mental and the organic material do not exhibit hydrocarbon contains to supply the enormous amount of petroleum found. The presence of helium and 13C isotope in the hydrocarbon adds strength to this theory, but this theory is not widely accepted.
Oil companies explore on the basis of biogenic theory. Here comes the greatest headache to the oil companies “how to locate oil at a particular place exactly”.



Exploration of Oil and Gas
Locating a place for drilling to find oil is a great task. The primary search of hydrocarbon begins with observation of surface terrain like faults and anticlines at a surface because it may be the indication of potential structural trap under the earth. Usually oil is found in sedimentary rocks. Now a day’s modern technique is used to locate oil field. Three main primary techniques used are Geophysical, Remote sensing and wild catting.




1. Geophysical
This technique involves
- Measuring electrical current, gravitational, magnetic anomalies, heat flow,geochemical relationship and density variations from deep within the earth.
- Interpreting the data to locate the presence of hydrocarbon under the earth.
Seismic Survey
a) Onshore
This technique involves
- Use of vibrations to get the picture of subterranean rock formations at the depth of 30000 feet below ground level with the help of explosives or vibrating trucks.
- Reflected vibration is detected by geophones.
- Recorded in magnetic tapes and printed in 2D graphs.
- These 2D graphs give us subsurface geology.
b) Offshore
- Vibrations are produced by dynamites or by compressed air.
- Detected by hydrophones
- Similar graphs are plotted as in onshore process.
- 3D seismic surveys are accurate but costly ($30,000 per mile).
2. Remote Sensing
- Satellite photographs are used to map the surface area.
- Gives clear picture of various information like soil moisture, soil type, mineral, etc.
- A type of RS is Side Looking Airborne Radar (SLAR) which is widely used now.
- It is a secondary process and the cost involved is huge.
3. Wild Catting
- Well is drilled in a new place based on photography, knowledge, and experience in a particular area.
- Probability of failure in this method is high.


- Arivazhagan.R