Classification of crude oil: Crude oils are classified on the basis of the various structural types of HCs. i.e Alkenes , cyelo alkanes, aromatics and s-o-n compels present in it . the

classification also considers sulphur content of the crude oil. Crud oils are

considered as para-ffinic or alkanic if the total content of saturated HCs is

greater than 50% of a particular crude oil. It is considered as aromatic if the

total content of aromatic resins and asphaltens is more than 50%. The

aromatic oils are further divided on the basis of naphthene % and sulphur

content.

Concentrate Type of crude oil S content

S > 50% P>N &P>=40% Paraffinic oil < 1%

AA < 50% P>=N & N<= 40% Paraffinic-Naphthenic < 1%

N>P & N>40% Naphthenic < 1%

S <= 50% P > 10% Aromatic-Intermediate >1%

P>10% & N<=25% Aromatic Asphalthic >1%

AA >= 50% P>=10% N>=25% Aromatic Naphthenic < 1%

S : Salurates AA: Asphaltene + Resin P : Paraffin N : Naphthenes

Physical Properties of crude oil: The Physical Properties of crude oil affects its migration and accumulation into pools. The detection of oil as well as its recovery from the oil well depends on the Physical Properties of the oil. Following are the commonly studies Physical Properties of crude oil . 1. colour:

it varies from colorless to pal amber to black. Commonly crude oil appears brownish red in transmitted light and greenish in reflected light. Heavier oils are blackish in color.

2. odour: crude oil having a large proportion of aromatics gives pleasant odour, in case of paraffin and haphthene based oil, odour is agreeable while oil having higher amount of complex heavier HCs. Alongirth S, N and O compels . gives disagreeable one.

3. specific gravity:

it varies from 0.55 to 1 . it is an important property as price of the crude oil dependa on it. As a rule , lighter the oil, higher is the proportion of commercially more important HCs present in it. And therefore higher is its price . In general paraffin. Based oil is better priced than asphalt-based oil. For measuring sp. grav. An arbitrary scale devised by API is in use. In this scale sp. grav. Of water is taken as 10 ْ API. The liquids having lower and lower sp. grav. Than water receive higher and higher number of the API degree. i.e. API degree shows inverse relationship with specific gravity. API ْ =(141.5 / specific gravity at 60 ْ F) – 131.5 By convection oil with than 30 ْ are considered as light those between 22 ْ API and 32 ْ API are medium and those with values below 22 ْ API are considered as heavy oils . the most favored grade of oil is 37 ْ API. Crude oils with this specific gravity are common in middle east , Alberta and north sea . very light crude oil above 40 ْ API occur in Algeria , Indonesia , SE Australia etc. For the aromatic base cam bay crude oil average API value is 32 ْ API.

4. Viscosity of a liquid is a measure of resistance to flow or it is an inverse measure of the ability of a substance to inverse relationship with temperature and shows an inverse relationship with temperature i.e. as temperature increase , fluid becomes more and more mobile. For oil industry it is an important property as the recovery of oil from oil well as well as handling of oil depends on its viscosity. Eg: in case of highly viscous oil , heating is required for its pumping as well as transport along with temperature .amount of gas dissolved in oil also affect its viscosity as the gas percentage present in gas increases its viscosity decreases . viscosity mainly depends on the number of C atoms present in a member of HC series. Viscosity is conventionally measured in centipoises 1 centipoises being viscosity of water at 20 ْ C. viscosity is more conveniently measured in time units in oil industry i.e. no. of seconds needed for a steel ball to roll through a standard volume of fluid. Such a unit is named say bolt universal second (SUS). SUS = (viscosity in centipoises x 4635 )/(elative density) Oil varies in viscosity from 1000 SUS to 50 SUS.

5. Refractive index: It is defined as a ratio of sine of angle of incidence to sine of angle of for crude of RI varies from 1.39-1.49 viscosity depends on the specific gravity .

heavier the oil, higher the RI. It is used in refinery operations.

6. fluorescence: all crude oils exhibit fluorescence. Aromatic base oils