Case04 Hydrocarbon kinetics Porosity update flag
Contents
The present case is a variation of Case01a with the first four layers in the column model containing kerogen 'B'. The only difference in this example is the definition of porosity update flag. By default, the porosity update flag is on. By switching this off, i.e. setting porosity update flag to zero, no porosity update due to hydrocarbon kinetics is taken into consideration. This examples serves to demonstrate the influence of porosity change due to hydrocarbon kinetics with the default ON or OFF porosity update flag.
It is recommended to undertake Case01 beforehand. The data is identical to the Case01a data with the addition of the porosity update flag in the Hydrocarbon_kinetics data structure. The data file for the project is in : Kin_001\Case04\Data.
Data File (.contact) |
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* Hydrocarbon_kinetics NUM=0 ! ---------------------------------------
(.....)
Porosity_update_flag 0
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1Porosity_update_flag is set to 0, i.e. no porosity update due to hydrocarbon kinetics is taken into consideration.
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The result files for the project are in directory: Kin_001\Case04\Results. Results of the high definition history files for the output variables including the hydrocarbon kinetic state variables have been processed into the excel file 00_Kin_001_Case04_Results.xlsx. Some of the graphical plots are presented here. The influence of the porosity change due to hydrocarbon kinetics is presented here with comparison reference to the Case01a example with default porosity update ON. •Case01a - Porosity update ON (default). •Case04 - Porosity update flag = 0 (OFF).
As expected, when the porosity update flag is set to OFF with no porosity change from the hydrocarbon generation taken into consideration, the stresses are very similar to the no kerogen case.
The comparison plots below show a slight increase in porosity from the no kerogen case for the case with the porosity update flag OFF. Although no porosity change from the hydrocarbon is taken into consideration, a consequence of the transformation from kerogen to hydrocarbon is a reduced density which in turn has other consequences. Density of hydrocarbon is approximately 850 kg/m3 compared against kerogen density of 1200 kg/m3.
The figures below show a marginal increase in the pore pressure for the update flag OFF case compared against the reference no kerogen case. This corresponds to the slight reduction in stress in the first four kerogen layers. With the porosity update flag OFF case, there is no increase in pore space due to the expulsion, therefore no weakening of rock allowing for further compaction, no higher perm associated with the porosity increase from expulsion and only the reduced density of hydrocarbon from kerogen transformation taken into consideration. This causes a slight overpressure.
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