--> Compositional Kinetics with a PVT Description Applied to the Prediction of Petroleum Quality in Brazilian Basins, Penteado, Henrique L.; Araujo, Laury M., #90100 (2009)

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Compositional Kinetics with a PVT Description Applied to the Prediction of Petroleum Quality in Brazilian Basins

Penteado, Henrique L.1
 Araujo, Laury M.1

1E&P Dept, Petrobras S.A., Rio de Janeiro, Brazil.

A compositional kinetic model for primary and secondary cracking using classes for petroleum PVT modeling has been developed for Brazilian lacustrine and marine source-rock sequences. This kinetic scheme has been widely applied in 3D petroleum systems modeling in Brazilian marginal basins to assess timing of oil and gas generation, as well as for the prediction of petroleum composition and PVT properties.

A total of more than 70 non-biodegraded oils from both lacustrine and marine source rocks, with API gravities ranging from 27 to 55, was submitted to quantitative gas chromatographic analyses. The oils were sliced according to boiling point and molecular weight ranges, and the mass percentages of each slice from C6 to C60+ were estimated. With these results, a PVT-type description of compound classes was adopted for the oil phase. Combining results for the oils with those for the gas phase, an enhanced PVT description was achieved for the whole petroleum (C1 to C60+).

The kinetics for primary cracking of lacustrine and marine source rocks were derived from Rock-Eval data, with corrections introduced for the actual petroleum expulsion efficiency. The initial composition attributed to the expelled petroleum from each type of source rock was that of the least mature, non-altered natural petroleum equivalent. As kerogen cracking proceeds, heavier and less stable compound classes can undergo secondary cracking, thus producing lighter and more gas-rich petroleum. The kinetics and stoichiometry of secondary cracking of each compound class were derived from experiments of artificial cracking of oils using several pyrolysis techniques. By coupling the primary and secondary compositional kinetic schemes, petroleum composition and its PVT properties (density, API gravity, GOR, saturation pressure) can be continuously assessed throughout source rock maturation.

Petroleum compositions provided by this new PVT-type kinetic scheme reproduce well those of real accumulations in Brazilian marginal basins, thus allowing its application as a powerful predictive tool in exploration prospects in frontier areas. Furthermore, the correlation of petroleum composition with source-rock maturity made possible by this kinetic scheme allows the oil composition of discovered accumulations to be used as calibration for source-rock evolution in petroleum systems modeling.

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil