(729d) Modeling of the Rate of Oil Vaporization From GOM Oil Spill

Following the accident at Macondo Well in the Gulf of Mexico (GOM) on April 20, 2010 oil spewed at a rate of 57000 barrels per day on a continuous basis until the well was fully closed on July 15, 2010. During this period nearly 5 million barrels of oil poured into the sea causing the worst oil spill and environmental disaster in the US history. A large portion of this oil (40 ºAPI) was vaporized during a period in which temperature varied from 20 to 34 ºC causing environmental and safety problems in the air especially in the vicinity of water surface. Knowledge of the amount of oil vaporized versus time is very important in the planning of clean up operations following an oil spill accident.

The purpose of this work is to present a mathematical model in which the amount of oil vaporized can be estimated versus time when oil is released from a damaged well. Complete data on low and high temperature, wind speed and humidity was obtained for the period of May, June and July, 2010 on daily basis. The oil API gravity was used as the only available specification of oil and a distribution model was used to split the crude into 20 pseudocomponents [1]. Characterization parameters for these components were calculated using methods available in the literature [2].

The model on the rate of oil vaporization and mass transfer coefficient in the air was developed based on a modified version of our previous analytical model [3]. In this model a time step of 12 hours ( ½ day) was used in which during each time step temperature, wind speed, surface oil area and its composition were kept constant. However, after calculating the amount of oil vaporized in each time step, new values for the oil volume, surface area, temperature and wind speed were used for the next round of calculations. In the model, it was assumed that the components with specific gravity greater than unity (heavier than water) immediately disperse into water column or sink to the sea floor so they do not enter the calculations for vaporization. 

Results of calculations show that as the leak was completely sealed (July 15_, 2010), about 50% (by volume) of total oil gushed into sea water surface was vaporized and 20% sank into the sea. NOAA [4], a US government agency which monitored the GOM oil spill throughout the crisis, estimated that from total amount of oil released about 24% was dispersed and 26% remained on the sea surface. Our calculations showed that about 29% was remaining on the sea. Considering that parts of oil was burned or, the proposed model predicts fairly well with actual field data and it can be used for a quick prediction of fate of an oil spill with continuous flow of oil based on minimal data available.

Acknowledgement

The funding for this project was provided by the Research Administration of Kuwait University under contract Project No. EC02/10.

 

References

[1] Riazi, M. R.,  1997, Ind. Eng. Chem. Research, 36, 4299-4307.

[2] Riazi, M. R.,  2005, Characterization and Properties of Petroleum Fractions, ASTM International, USA..

[3] Riazi, M. R., Al-Enezi, G., 1999, Chem. Eng. J. 73, 161-172.

[4] National Oceanic and Atmospheric Administration (NOAA), www.noaa.gov, accessed during the period:  April – July 2010.