Introduction to Petroleum Industry

Dr. Fatma Ashour

INTRODUCTION

• Petroleum is the general term given to Hydrocarbon Mixtures found in nature below the surface of the earth.

• Petroleum occurs either in

Gaseous form called Natural gas Liquid form called Crude Oil Solid form called Bitumin or Pitch

Impurities• Petroleum is mainly composed of Hydrocarbons [compounds containing

C & H only]; any compound which is not a hydrocarbon is considered an impurity.

• The most important impurities are :

Organic ‘S’ compounds (eg: H2S and Mercaptans)

Organic 'N' compounds (eg: pyridine derivatives)Other impurities are present namely:O2–compounds (eg: oxides, carbonates and sulphates)

P -coumpoundsMineral Salts (eg: NaCl and MgCl2)

Mineral elements (eg: Vanadium and Nickel)

Uses

• Petroleum, as found in nature, cannot be directly used, it has to be refined &/or separated into various fractions before it can be marketed.

• The main uses of Petroleum Products are:

As a fuel (eg: Natural gas, gasoline, Diesel Fuels and Fuel Oil)As a source of heat and power generation (eg: Kerosene and Fuel Oil)As a lubricant (eg: Lubricating Oils & greases)As a raw material for the Petrochemical Industry (eg: Natural gas and

Naphtha)

Atmospheric-Vacuum Distillation Complex

Petrochemical Industries

• These are industries in which Petroleum is used as a raw material. The most important of which are: -

Manufacture of H2 (hence NH3 & the main fertilizers…….etc).

Manufacture of olefins – hence the Plastics , and synthetic textile industries…etc)

Manufacture of Aromatics (hence synthetic rubber……..etc).

TECHNOLOGY OF THE PETROLEUM• The Technology of the Petroleum Industry maybe divided into FOUR main

Operational Stages:

• Exploration (ie: Prospecting & Drilling) for Natural gas or crude oil and their Commercial ‘Production’ when found.

• Transportation of Natural gas to gas plants and crude oil to refineries as well as petroleum products from refineries to markets.

• Marketing and Selling of Natural gas &/or crude oil to millions of consumers with the elaborate storage and distribution facilities within marketing areas.

• Processing or Refining, whereby both Natural gas & crude oil are processed / refined into consumable products.

Crude Oil

• Origin & Theories• The question of the origin of crude oil in nature is

important for oil exploration.

• Many theories have been suggested to account for the origin of petroleum in nature, the most important of these are:

The Inorganic Theory The Organic Theory

Carbide theory

• Hydrocarbons present in petroleum are formed by the action of water on inorganic carbides. They are formed by the reaction of metal and carbon under high temperature & pressure conditions inside the earth.

Ca +2C CaC2

4Al + 3C Al4C3

CaC2 + 2 H2O Ca(OH)2+C2H2

Al4C3 +12H2O 4Al(OH)3+3 CH4

These lower hydrocarbons then undergo hydrogenation and polymerization to give various types of hydrocarbons( paraffins, aromatics and cycloparaffins)

• However , this theory fails to explain the following facts:

• Presence of nitrogen and sulphur compounds• Presence of chlorophyll and haemin• Presence of optically active compounds

The Organic Theory ( Engler 1890)(widely accepted theory)

According to this theory, certain places have been covered by the sea during early geologic ages. Such waters (shallow waters) are rich in animal or vegetable life (usually ‘marine organisms’, large or microscopic).

• On dying, marine organisms sink to the bottom of the sea and are buried; later on, the sea shores recede leaving these deposits (remains) as a surface layer on the land.

• Geologic variations result in covering these remains by layers of mud, causing the marine deposits to be buried deep below the surface of the earth.

• Mud accumulates on the thick layers containing the organic matter, causing high pressures and high temperatures. Such conditions, assisted by the bacteria and possibly radio-activity transform organisms by a fermentation process to hydrocarbons in the form of gas or oil.

• The organic theory explains the presence of N and S compounds, chlorophyll and optically active compounds.

OILFIELD REFINING

• In general crude oil (or Natural gas) receives some primary refining at the oil (or gas) field. This is because, the oil (or gas) produced at the well head is usually associated with:

- Petroleum gases (natural gas)- Connate water.- Sand.

• Such, so called crude impurities, must be removed before the oil is distributed to the storage tanks and, consequently transported to the refineries.

It is common practice that, the production from each well is led through a ‘flowline’ from the well head to a ‘gathering station’. This gathering station handles the production from several wells in its vicinity and is equipped with ‘gas separators’ (cyclones) and with ‘settling tanks’ in which the oil can be stored (or guaged out) and from which water-which settles out-could be drained off.

GOSP Flow Sheet

Removal of Gases

• Gases associated with crude oil must be removed before transportation to the refineries. This is because such gases raise the vapour pressure of the oil and thus increase fire hazards.

• Gases are removed in special “gas separators” which vary widely in their detailed construction according to the capacity required and the operating pressure.

• They consist essentially of vertical or horizontal cylindrical vessels containing baffles against which the oil/gas mixture is directed.

• The separated gases leave through an outlet, at the top of the tank, while the liquid (Oil), free from gases, collects at the bottom.

• The efficiency of separation is sometimes increased by installing settling tanks in the form of a cyclone ‘cyclone settlers’. The crude oil enters tangentially to the rotating vessel thus acquiring a spiral path and, consequently, increasing the efficiency of separation.

• If the pressure of the gases produced from the well head is high, it can be reduced in steps by installing more than one settling tank in series.

Removal of Water• The oil produced from the well head is generally associated with variable

quantities of water (connate or edge water) known as ‘formation water’. The crude oil must be dehydrated before being distributed to the refineries. Such dehydration operation is carried out because:

• - It prevents any unnecessary rise in the transportation cost.• - It prevents any erosion of the pipelines used in transportation

Formation water in found in TWO forms:

Free Water : This water can be easily separated from the oil by gravity settling in the tank at the gathering stations and later also at the main storage tanks.

Water emulsified with the oil

• This water often occurs in the form of an emulsion with the oil and would not readily settle out. In such emulsions the water exists as fine droplets of microscopic size.

• To extract it from such an emulsion, the droplets must be made to coalesce into drops of a larger size, hence they will sink through the lighter oil and form a layer beneath the oil.

Demulsification methods:

1- Heating: This has the effect of softening the coating which Separate the oil from the water, and

thus promote coalescence to larger size molecules through mixing or agitation.

2- Addition of Special Chemicals Chemicals have the effect of partially dissolving the resinous coating surrounding the

water droplets i.e. they reduce the interfacial tension between the oil and the water. (sulphonated oils, detergents and salts (similar to Na2 CO3)).

• 3- Electrical Method It has been found that the coatings surrounding the water droplets are electrically

charged. Emulsion is subjected to a high potential difference the water droplets will move towards the electrodes at opposite sign. An alternating current (In the range of 30.000-33.000 watts) is therefore used in this method whereby the droplets will be subjected to vigorous reciprocating motion, during which several droplets collide with one another. Such collisions result in larger droplets which are easily separated by gravity settling.

Removal of Sand

• Oil produced from the well head is generally associated with sand, resulting from the breaking down and fragmentation of the porous formation containing the oil.

• Sand is removed by “Gravity Settling” actually, the same settling tank used to remove water is generally used for the simultaneous removal of sand. The apparatus consists essentially of a settling tank whereby the oil its separated from the sand. The latter is withdrawn from the bottom of the tank while the clean crude oil is taken from a side opening above the sand layer.

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High Pressure separature