Val_005b Oil to Gas Cracking

Contents

Problem Description

The user is assumed to have undertaken the example Val_005a beforehand.

The oil to gas cracking process is described here as highlighted in Figure 1. Five thermal field simulations, one for each of the five pre-defined kerogen organofacies A, B, C, D/E utilising the default kerogen kinetics parameters are performed. The ParaGeo results are compared against the results presented in Pepper and Dodd (1995) - [Figure 11].

Val_005b_001

Figure 1: Scheme of petroleum generation, cracking, expulsion, porosity change and pore pressure generation. Highlighted process is the Oil to Gas cracking.

The hydrocarbon kinetics input parameters for the oil -> gas cracking for the different organofacies A - F are shown in Table 1 below. Note that the oil -> gas pre-multiplier value is a calibrated value to the reference solution for both oil -> gas cracking results presented here and in the oil and gas expulsion results presented in Val_005c.

Hydrocarbon kinetics parameter	Definition
Oil gas cracking model	GaussHI
Oil gas cracking premultiplier A0	0.1E15 Ma-1

Table 1: Hydrocarbon kinetics oil -> gas cracking input parameters

Data File Description

The data files for the oil -> gas cracking process are in ParaGeo Examples\Validation\Val_005\Val_005b\Data. The model data for each of the organofacies types A - F is similar to Val_005a (default case) with the exception of the hydrocarbon kinetics data. Only this data structure is described here.

Hydrocarbon_kinetics

Hydrocarbon_kinetics defines the assignment and processing data associated with hydrocarbon kinetics, e.g. vitrinite maturation, oil -> gas cracking, hydrocarbon expulsion, hydrocarbon density for porosity update and pore pressure generation.

Data File

* Hydrocarbon_kinetics NUM=0

! ---------------------------------

Maturation_model 'EasyRo'

Oil_gas_cracking_model GaussHI

Oil_gas_cracking_premult 0.1E15

Hydrocarbon_density_model "Constant"

Hydrocarbon_density_properties IDM=1

898

1Oil -> gas cracking model is defined as "GaussHI". Note that this setting uses the default parameters for the activation energy constants and variance constants as defined in Hydrocarbon_kinetics (i.e. a1 = 233.6 kJ/mol, b1 = 7.5 kJ/mol, a2 = 32.5, b2 = 8.55).

2The pre-multiplier A0 is defined as 0.1E15 Ma-1.

Results

The results files for the oil -> gas cracking for kerogen organofacies types A - F are in ParaGeo Examples\Validation\Val_005\Val_005b\Results. In this directory the spreadsheet mat_kerogen_o2g_no_expulsion.xlsx contains the history results output from the simulations and comparison plots against the results presented by Pepper and Dodd (1995) - [Figure 11] for organofacies types A - F.

Figure 2 below shows a comparison of the ParaGeo results against the results presented by Pepper and Dodd (1995) - [Figure 11] for organofacies types A - F. These show excellent correlation between the two sets of results.

Organofacies	(a) ParaGeo vs Pepper and Dodd (1995) - [Figure 11] (b) ParaGeo
A
B
C
D/E
F

Figure 2: ParaGeo vs Pepper and Dodd (1995) - [Figure 11]: Oil -> Gas cracking transformation profiles for organofacies types A - F

References

[1] Pepper, A.S. and Corvi, P.J. (1995(a)): Simple kinetic models of petroleum formation. Part I: Oil and gas generation from kerogen. Marine and Petroleum Geology. 12(3) 291–319. 1995(a).

[2] Pepper, A.S., Dodd, T.A. (1995): Simple kinetic models of petroleum formation. Part II: Oil-gas cracking. Marine and Petroleum Geology. 12(3) 321-340.

[3] Pepper, A.S. and Corvi, P.J. (1995(b)): Simple kinetic models of petroleum formation. Part III: Modelling an open system. Marine and Petroleum Geology. 12(4) 417-452.

[4] Sweeney, J.J. & Burnham, A.K. (1990): Evaluation of a simple model of vitrinite reflectance based on chemical kinetics. AAPG Bull. 74 10., 1559 – 1570.