Method of quantifying hydrocarbon formation and retention in a mother rock

Abstract

The method according to the invention allows the formation of oil and the retention phenomenon in the mother rock to be modelled. Organic matter characterization experiments are used to establish the molecular model (MM) of the initial sample (E). The thermal cracking reaction of this molecular model is reproduced by dynamic molecular simulation computations with a reactive force field (RMD) and validated by comparison with experimental data. The reaction mechanism obtained (SR) allows to carry out a kinetic study (C) by variation of the temperature parameter. The phase equilibria (PES) of the reaction medium are determined at any time from dynamic simulation. The successive phase equilibrium assessments at various progress stages of the cracking reaction allow following the physicochemical evolution (PC) of the thermal maturation of the organic sample studied. The free hydrocarbons (liquid and gaseous) that are not retained in the solid residue can be quantified throughout numerical modelling of the sample maturation; representing, in the sedimentary basins, the hydrocarbons that are not retained in the organic matrix of the mother rock (Q). This quantity can be used as an indicator or an input value for the retention threshold in basin models.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method of quantifying hydrocarbon formation and retention within a macromolecular chemical system. [0003] 2. Description of the Prior Art [0004] The following documents, mentioned in the description hereafter, illustrate the state of the art: [0005] Behar F., Vandenbroucke M., Tang Y., Marquis F., Espitalié J., 1997. Thermal Cracking of Kerogen in Open and Closed Systems: Determination of Kinetic Parameters and Stoichiometric Coefficients for Oil and Gas Generation. Org. Geochem., 26, 5-6, 321-339. [0006] Burnham, A. K. and Braun, R. L., 1989. Development of Detailed Model of Petroleum Formation, Destruction, and Expulsion from Lacustrine and Marine Source Rocks. Advances in Organic Geochemisrty, 16, 1-3, 27-39. [0007] Burnham, A. K. and Braun, R. L., 1990. Mathematical Model of Oil Generation, Degradation, and Expulsion. Energy and Fuel, 4, 132-146. [0008] Faulon, J. L., Predictio...

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Problems solved by technology

's work of 1997 showed that the differences in the experimental conditions of the pyrolyses carried out (open or closed medium, in the presence or absence of water or of mineral matrix, or according to the grain size of the sample) leads to a kinetic parameters lag and therefore to an uncertainty in the estimation of the oil window.

On the other hand, the complexity of these models makes elaboration of the reaction mechanism difficult.

Finally, and above all, the very large number of reactions in these models is incompatible with current basin simulators.

The polymer solubility theory and this model thus do not totally explain the hydrocarbon composition differences between mother rock extracts and reservoir oils, observed in petroleum systems.

Similarly, this model does not explain the great accumulation of aliphatic hydrocarbons in coals.

This model has two limitations: the first one is that the values of the swelling ratio are filed according to their chemical class but they are not normalized.

Thus, the model does not respect the mass conservation principle.

The second drawback is due to the fact that the swelling phenomenon involves swelling of the organic matrix.

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