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Wax and Flow Assurance
The crude oil composition influences the evacuation of crude oil in several ways. Paraffin wax and asphaltenes present in crude oil can affect crude oil production by deposition at wellbore, in tubing or in the pipelines. The inorganic constituents like calcium, barium, strontium etc. can obstruct flow by forming scale especially at wellbore, in tubing or in a choke.

Wax is an alkane with carbon number varying from 16 to 70. Wax is dissolved in crude oil under reservoir conditions and during flow from the reservoir to wellbore to wellhead and to surface, temperature and pressure change. This results in the separation and deposition of wax at different locations, depending upon characteristics of wax and temperature-pressure equilibria.

There are two important terms related to wax: pour point and cloud point. Cloud point is the temperature below which wax forms a cloudy appearance and is also known as Wax appearance Temperature and at that temperature waxes thicken the oil. The pour point of crude oil, or a petroleum fraction, is the lowest temperature at which the oil will pour or flow when it is cooled, without stirring, under standard cooling conditions. The pour point of crude oils relates to their paraffin content: the higher the paraffin content, the higher the pour point and the higher the pour point, the more are flow assurance problems. Below the pour point temperature, pumping and transportation problems may be encountered. Along with viscosity, the pour point is also used in pumping and design calculations.

The following factors influence the wax deposition:
- Temperature
- Crude oil composition
- Pressure
- Flow rate
- Gas / Oil ratio

The following wax remediation techniques are used, in combination or alone:
A.   Thermal
- Hot oiling
- Hot water
- Direct heating
B.   Chemical
- Solvent
- Wax crystal modifier
- Dispersant
- Surfactant
C.   Mechanical
- Mechanical / manual stripping
- Pigging
D.   Thermo-chemical
E.   Microbiological

Applications of Surfactants in the Petroleum Industry

Ref: J. DISPERSION SCIENCE AND TECHNOLOGY, 14(I), 87-116(1993)
By Dr. Anil Bhardwaj1, S. Hartland2, Department of Chemical Engineering and Industrial Chemistry
Swiss Federal Institute of Technology, CH-8092, Zurich, Switzerland

ABSTRACT
Surfactants find applications in different operations of petroleum production. They have become important in drilling; cement Sherries, fracturing, acidization, demulsification, corrosion inhibition, transportation, cleaning, water flooding, chemical, foam and steam flooding and environment protection. They are essential to the improvement of production economies and total recovery of petroleum. This review describes those points of applications, Logic behind their use and more common formulations.

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