The challenge:
The stability of linear alkanes dissolved in the oil at the reservoir temperature may be affected by the thermal profile during production, transportation and storage operations. During cargo transportation in cold areas, the temperature of the oil decreases slowly, and the paraffinic fractions of the oil start to crystallise, causing gelling of the oil, and sludge deposits at the bottom of the tanks.
The solution: increase the performance with dedicated solutions.
To overcome problems like these, a pour point depressant (PPD) is injected into the oil as far upstream in production as possible. By modifying the crystallisation pattern of the wax, this chemical lowers the pour point of the oil, and prevents paraffin crystals from settling.
Recently, a 150,000 T cargo of paraffinic oil (pour point 30°C) was treated at export facilities in western Africa with 300 ppm of CECA PROCHINOR® AP 880. The PPD was heated up to 40°C, and continuously injected into the oil at 55°C (above the wax crystallisation temperature), at the outlet of the desalting plants. The 150,000 T tanker was then loaded. The temperature of the oil in the tanks was 48°C.
The injection rate and the treatment formulation were recommended on the basis of the results of a laboratory study conducted both in our research centre in France and locally.
The benefits:
After two weeks’ transportation from western Africa to France, the temperature of the oil was less than 20°C in the colder tanks (in the front of the tanker). The oil was homogeneous (no sludge or deposit) and liquid (pour point 12°C). As the rheological behaviour of the oil was improved by the PPD’s effect, the transfer operations to the refinery storage facilities were completed within 23 hours, with no back pressure or troubleshooting in the export lines.
This kind of heavy paraffinic oil usually needs to be maintained at 40°C during transportation, and flushing operations are required to recover the sludge that has built up. In this particular case, it was not necessary to heat the oil or flush the tanks, thanks to the efficiency of the treatment.
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