الفهرس | Only 14 pages are availabe for public view |
Abstract Petroleum is the major energy source all over the world. It is a complex mixture of hydrocarbons and mainly composed of paraffins, olefins, and aromatics. Paraffin wax is high molecular weight straight chain alkanes with 16 or more carbon atoms. Paraffin remains in equilibrium in liquid state, but once the crude oil is pumped out from the reservoir, the pressure and temperature are reduced; viscosity of the crude oil is increased, the paraffinic hydrocarbons (wax) start to precipitate out of the crude oil on the pipe walls decreasing the inner diameter of the pipeline causing difficulties in the extraction, problems in transportation process, especially during wintertime. This is one of the most important problems in any oil field producing paraffinic crude oils, and costing the companies millions of dollars per year. There are approaches used for managing paraffin deposition in oil fields: (1) Mechanical, (2) thermal, (3) chemical, and (4) microbial. The mechanical method is used to remove paraffin deposition mechanically using devices known as scrapers or cutters. Thermal method is used by increasing the temperature by injection of hot steam or hot oil between tubing and casing. Chemical method can be used by injecting agents to dissolve paraffin or changing wax crystal structure which prevents paraffin crystals from depositing by altering their growth. The chemicals used are toxic and cause great damage to the environment and cause long-term damage to the pipelines and wells. Therefore, microbial degradation of paraffinic compounds has gained considerable interest for many reasons: it is easy to handle, eco-friendly, noncombustible, non-carcinogenic, and nonpathogenic, and it has low toxicity. Microbial degradation is also of low cost when compared to chemicals prices. Removal of paraffin wax by microorganisms is based on their ability to degrade viscous long chain hydrocarbons into short-chain non-viscous ones. They can also change the structure and decrease the size of paraffin crystals which will improve the fluidity of crude oil. Many microorganisms, such as Pseudomon as, Acinetobacter, Rhodococcus, Bacillus and many more, can degrade alkanes/paraffins, as they use them as a source of carbon for their nutrition and growth. |