Many oil fields producing waxy crude, face severe wax deposition problem in down hole tubulars and surface flow lines. Sometimes this problem is also encountered at the face of producing zone in the well bore region due to changes in temperature & pressure conditions. This problem frequently results in complete blockage of the crude passage and poses severe production problem. Conventional methods such as thermal, magnetic, mechanical scraping, solvent cleaning and chemical treatment etc. are not only cumbersome, costly and hazardous but provide only temporary respite. Two separate microbial systems, capable of mitigating the vexed problem of paraffin deposition in oil well tubulars and surface flow lines have been developed.The microbial system for down hole tubular comprises of paraffin degrading bacterial (PDB) consortium named as PDS-10, nutrient supplements and growth enhancer. Laboratory studies showed significant reduction in pour point and flow behaviour of the crude. The process is effective up to 90 0 C but maximum efficiency was observed at 55 0 C. Field trial in 100 wells of different fields of Western & Eastern sector has shown that the treatment not only checked the paraffin deposition in all the treated wells but also improved oil production by 20-80 % in many wells. Most of the treated wells flowed without any wax deposition for 6-8 months after the treatment.For flow assurance in surface flow lines bacterial consortium named as FIB-19, which shows high degree of wax degradation capability has been developed. The bacterial consortium is aerophilic, mesophilic and remains active upto 43 0 C. Field trial in surface flow lines of twelve wells of Ahmedabad Asset was quite successful resulting in elimination of requirement of line flushing for considerable time along with reduction in pressure in the flow line. The average period of effectiveness of the jobs has been found to be around 4-5 months.

Severe wax deposition problem is encountered in down hole tubulars and at the face of producing zone in the well bore region and surface flow lines of most of the oil fields producing waxy crude. Paraffin in the crude begins to precipitate and deposit around well bore and tubulars as the pressures and temperatures decrease, frequently resulting into partial/complete blockage of crude passage and pose severe production problems. Traditional methods such as thermal, magnetic, mechanical scraping, and chemical treatment etc. are not only cumbersome, costly and hazardous but also provide temporary respite. Use of microbes, a novel approach was conceived to find alternate effective solution. Institute of Reservoir Studies (IRS), ONGC, has developed two separate microbial systems for mitigating the vexed problem of paraffin deposition in oil wells and surface flow lines. The microbial system for down hole tubulars comprises of paraffin degrading bacterial (PDB) consortium, nutrient supplements and growth enhancer. The bacterial consortium, is naturally occurring, micro-aerophilic, thermophilic, capable of degrading paraffin up to 90°C. Paraffin degrading ability was maximum at 55°C which is the temperature around which most paraffins get deposited. The candidate wells having severe wax deposition problem, were selected from different fields of Mehsana Asset of ONGC. Application of the technology has been done successfully on commercial scale in 45 wells (48 jobs) of Mehsana Asset. The microbial treatment not only checked the paraffin deposition in all the treated wells but also improved oil production by 20-80% in many wells. Most of the treated wells flowed without any wax deposition for 6-8 months after the treatment. Some of the wells even flowed for over a year giving average success ratio of around 70%. Net incremental oil gain from 48 jobs was around 4000 m3. Bacterial consortium, named as FIB-19, showing 67% wax degradation at 37°C prevents wax deposition in surface flow lines. The bacterial consortium is micro aerophilic, mesophillic and remains active upto 43°C. Application in surface flow lines of ten wells of Mehsana Asset was quite successful resulting in elimination of requirement of line flushing for considerable time along with reduction of pressure in the flow line.

No abstract