Petroleum and derivatives such as asphalt have been known and used for almost 6000 years and there is evidence of use of asphalt in building more than 600 years ago. Modern petroleum refining began in 1859 with discovery of petroleum in Pennsylvania and subsequent commercialization. The exploration of petroleum originated in the latter part of the nineteenth century
Crude Oil and Natural Gas Origin, Occurrence, Exploration and Drilling
Oil and natural gas were formed hundred years ago from the prehistoric plant and animals. it is believed that hydrocarbon formed by the thermal maturation of organic matter buried deep in earth. over the millions of years under extreme pressure and high temperature these organic matter converted to hydrocarbons consisting of oil and gas. Hydrocarbons are present in the variety of forms: koregen, asphalt, crude oil, natural gas, condensates, and coal in solid form.
Oil and gas production includes exploration, drilling, extraction, stabilization. The underground traps of oil and gas are called reservoir. Various types of traps are structural traps, stratigraphic traps and combination traps Most reservoir contain water also along with oil and gas. Reserves are classified as proven, probable and possible reserves. Earlier finding of oil and gas was matter of luck and hit and miss process. Tools used for oil and gas exploration are based and dependent on gravity change, magnetic field change, time, change and electrical resistance. However it has become now more challenging and complex. With advent of three dimensional seismic technology which is based on the sound waves, identify the subsurface formation by reflection of sound, there has been much improvement in identification of oil and gas traps and reservoirs. Seismic technology significantly improves the method of estimating the oil and gas deposits. Next step after exploration is the drilling of exploratory well. Drilling may be vertical drilling or horizontal drilling. Drilling may be performed on-shore or off-shore. Horizontal drilling and hydro-fracturing has resulted in economical and more productive drilling of shale gas which was not economical with conventional vertical drilling.
Composition of Petroleum (Crude Oil)
Petroleum (Crude oil) consists of mainly carbon (83-87%) and hydrogen (12-14%) having complex hydrocarbon mixture like paraffins, naphthenes, aromatic hydrocarbons, gaseous hydrocarbons (from CH4 to C4H10). Table M-VI 1.1 gives more details about composition of petroleum. Besides crude oil also contains small amount of non hydrocarbons (sulphur compounds, nitrogen compounds, oxygen compounds) and minerals heavier crudes contains higher sulphur. Depending on predominance of hydrocarbons, petroleum is classified as paraffin base, intermediate base or naphthenic base.
Table M-VI 1.1: Composition of Petroleum
Methane, ethane, propane, butane, pentane, hexane
General formula CnH2n+2
Boiling point increases as the number of carbon atom increases. With number of carbon 25-40, paraffin becomes waxy.
Isoparaffins (Iso alkanes)
The number of possible isomers increases as in geometric
progression as the number of carbon atoms increases.
One pair of
General formula CnH2n
Olefins are not present in crude oil, but are formed during process. Undesirable in the finished product because of their high reactivity. Low molecular weight olefins have good antiknock properties.
5 or 6 carbon atoms in ring
General formula CnH2n+2-2Rn
Rn is number of naphthenic ring
The average crude oil contains about 50% by weight naphthenes. Naphthenes are modestly good
1,2 dimethyl cyclohexane.
components of gasoline.
6 carbon atom in ring with three around linkage.
Toluene, Xylene, Ethyl Benzene, Cumene, Naphthaline
Aromatics are not desirable in kerosene and lubricating oil. Benzene is carcinogenic and hence undesirable part of gasoline.
Hydrogen sulphide, Mercaptans
Undesirable due to foul odour
0.5% to 7%
pyrrole, indole, carbazole
The presence of nitrogen compounds in gasoline and kerosene degrades the colour of product on exposure to sunlight. They may cause gum formation normally less than 0.2.
Naphthenic acids, phenols
Content traces to 2%. These acids cause corrosion problem at various stages of processing and pollution problem.
Processing Of Petroleum (Crude Oil)
Crude Oil Processed In India
Figure M-VI 1.1: Oil and Gas Processing
Kuwait, Dubai, S. Arabia( Arab Mix, Arab medium), Iraq, Abu Dhabi, UAE(upper Zakum,Murban,UM Shaif)
Iran, Kuwait : Ratawai, Egypt( Suez Mix, Zeit mix),
Libya - Es Sider
Nigeria-Bonny Light, Eseravos, Forcados, Penington,
Angola, -Cabinda, Palanca, Girassol
Eq. Guinea -Ceiba, Zaffiro
Congo -Nikossa, Kitina
Malaysia -Labuan, Miri Light
Australia -Barrow Island, Cooper Basin,Chalis
Brunei -Seria Light
Table M-VI 1.3: Worldwide Crude quality
Residue in crude ,vol %
‘S’ in residue ,Wt %
Metals in residue, ppm
Sources of indigenous crude
Assam Crude Nahorkatia/
31 oAPI, Sulphur 0.3%, Pour point +30 oC, High aromatics, Total distillate yield 65%.
27 o API, Sulphur 0.3%, High aromatics, Distillate yield 57%.
48 oAPI, Sulphur 0.1%, Pour point +18 oC, Distillate
yield 80-82% (Light distillates 24%, Middle distillate 47%), Wax content 9.9%, total sulphur 0.02%.
North Gujarat Crude
28 oAPI, Sulphur content 0.1%, Pour point +27 0C, Distillate yield low 33-35%, High organic acidity.
Bombay High Crude
38 oAPI, Sulphur 0.2%, Pour point +30 oC, Distillate yield 65-70% (Light distillate 24%, Middle distillates 46%), High aromatics.
46 oAPI, Sulphur 0.1%, Pour point 3 oC, Distillate yield 80%.
KG Basin Ravva Crude
36 oAPI, Sulphur 0.1%, Pour point +30 oC, Distillate yield 61%.