Kerogen_kinetics

 

Data Structure: Kerogen_kinetics

Description

Defines the assignment and processing data associated with Kerogen_kinetics definition

Usage

Kerogen_kinetics     NUM=ival   where ival  is the data structure number

 

Description

Overview

This data structure defines the assignment and processing data associated with kerogen kinetics.

 

Screening of potential source rocks is performed by measurement of total organic carbon (TOC) content and Rock-Eval type pyrolysis yield (S1 and S2; sometimes P1 and P2), where:

 

•S1 = the amount of free hydrocarbons (gas and oil) in the sample.

•S2 = the amount of hydrocarbons generated through thermal cracking of non-volatile organic matter.

 

Reactive kerogen is thermally degradable: it is defined by the pyrolysis S2 yield and when the S2 yield is normalized to the TOC, the ratio is known as the hydrocarbon index (HI)

kinetic_001

 

HI therefore provides an indication of the reactive to inert kerogen proportions in the sedimentary organic matter (SOM).

 

Hydrocarbon yields are reduced to carbon equivalents using a factor W (e.g. W=0.85 ), which is the weight fraction of carbon in hydrocarbons. However, S1 sometimes is implicitly defined considering W, so that in this case W=1.0 (default value in ParaGeo).

 

The ratio of gas generated relative to oil ( G) is also defined. G differs from the often used expression ( GOGI ), but they are related (see Pepper and Corvi, 1995 Figure 2) reproduced here.

kinetic_012

 

The equivalent fractional carbon concentrations relative to the initial total carbon mass are then:

 

kinetic_002

kinetic_003

kinetic_004

kinetic_005

kinetic_006

 

and the reactive kerogen is defined as

kinetic_007

 

Key indices and quantities defining the conversion of kerogen to hydrocarbon are:

kinetic_008

kinetic_009

kinetic_010

kinetic_011

 

Note that Transformation ratio TR is also referred to as Transformation index TI in the manual.

 

Five pre-defined kerogen types are available defined by the organofacies presented by Pepper and Corvi (1995) (see table):

 

Name

Description

Principal Biomass

Sulphur

Environmental/Age

Possible IFP Classification

A

Aquatic, marine, siliceous or Carbonate/evaporite

Marine algae, bacteria

High

Marine, upwelling zones, clastic-starved basins (any age)

Type II'S'

B

Aquatic, marine, siliciclastic

Marine algae, bacteria

Moderate

Marine, clastic basins (any age)

Type II

C

Aquatic, non-marine, lacustrine

Freshwater algae, bacteria

Low

Tectonic non-marine basins, minor on coastal plains (Phanerozoic)

Type I

DE

Terrigenous, non-marine, waxy

Higher plant cuticle, resin, lignin, bacteria

Low

Some (Mesozoic and younger) 'ever-wet' coastal plains

Type III'H'

F

Terrigenous, non-marine, wax-poor

Lignin

Low

Coastal plains (Late Palaeozoic and younger)

Type III/IV

 

Alternatively user defined kerogen types may be defined using a Gaussian description or tabular definition of weights and activation energies.

 

Default kerogen - > oil generation kinetic parameters for the pre-multiplier A0, activation energy Emean and the variance σ for the five organofacies presented by Pepper and Corvi (1995a) are listed in the table below:

 

Name

A0 (1/s)

Emean (KJ/mol)

σ (KJ/mol)

A

2.13E+13

206.4

8.2

B

8.14E+13

215.2

8.3

C

2.44E+14

221.4

3.9

DE

4.97E+14

228.2

7.9

F

1.23E+17

259.1

6.6

 

Default kerogen - > gas generation kinetic parameters for the pre-multiplier A0, activation energy Emean and the variance σ for the five organofacies presented by Pepper and Corvi (1995a) are listed in the table below:

 

Name

A0 (1/s)

Emean (KJ/mol)

σ (KJ/mol)

A

3.93E+12

206.7

10.7

B

2.17E+18

278.7

18.4

C

2.29E+16

250.4

10.1

DE

1.88E+11

230.6*

7.7

F

1.93E+16

275.0

9.9

•*Pepper and Corvi (1995a) have deemed the default value of Emean =206.4 kJ/mol unreliable and unrealistic, thus the default is defined as 230.6 KJ/mol based on results calibrated to the reference solution.

 

Other default parameters in the kerogen kinetics for the five organofacies presented by Pepper and Corvi (1995) are listed in the table below:

 

Name

Transformation ratio*, TR

Hydrocarbon index, HI

Gas concentration ratio, G

Weight fraction carbon, W

A

0.033

0.617

0.17

0.80

B

0.018

0.592

0.17

0.75

C

0.020

0.600

0.13

0.68

DE

0.007

0.333

0.23

0.68

F

0.002

0.158

0.44

0.75

 

•*Note that Transformation ratio TR is also referred to as Transformation index TI in the manual.

 

References

•Pepper, A.S. and Corvi, P.J. Simple kinetic models of petroleum formation. Part I: oil and gas generation from kerogen. Marine and Petroleum Geology. 12(3) 291-319. 1995

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

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

 

 

Click to expand/collapseName    Name of kerogen data

Usage

Name

Character Name

 

 

Description

Defines the name of kerogen data (maximum 32 characters).

 

 

Click to expand/collapseKerogen_facies_type    Kerogen facies type

Usage

Kerogen_facies_type

Character Name

 

 

Description

Specifies the type of kerogen facies. Five pre-defined types as defined by Pepper and Corvi (1995a) with the names A, B, C, D/E, F are available. Alternativelly a user defined type may be specified. Consequently, valid values are:

 

• "A" - Marine, siliceous or Carbonate/evaporite organofacies from marine algae and bacteria. High sulphur content. Possible IFP classification as Type II'S'

• "B" - Marine, siliciclastic organofacies from marine algae and bacteria. Moderate sulphur content. Possible IFP classification as Type II

• "C" - Lacustrine organofacies from freshwater algae and bacteria. Low sulphur content. Possible IFP classification as Type I

• "D/E" - Terrigenous waxy organofacies from higher plant cuticle, resin, ligin and bacteria. Low sulphur content. Possible IFP classification as Type III'H'

• "F" - Terrigenous wax poor organofacies originating from ligin. Low sulphur content. Possible IFP classification as Type III/IV

• "DefineName" - User defined kerogen organofacies properties via Kerogen_gas_properties and Kerogen_oil_properties

 

Notes

•If a pre-defined type is selected then Kerogen_gas_properties and Kerogen_oil_properties are set by default.

 

 

Click to expand/collapseKerogen_gas_properties    Defines the properties for Kerogen->Gas conversion via a Gaussian distribution

Usage

Kerogen_gas_properties

IDM=ival

 

 

Real Values

 

 

 

 

where

ival

Number of kerogen gas properties

Description

Defines the properties for Kerogen->Gas conversion via a Gaussian distribution. The values comprise:

•Location 1 - pre-multiplier ( A0)

•Location 2 - activation energy ( Emean)

•Location 3 - variance ( σ)

 

Notes

•Default parameters are available for specific named kerogen types:

Name

A0 (1/s)

Emean (KJ/mol)

σ (KJ/mol)

A

3.93E+12

206.7

10.7

B

2.17E+18

278.7

18.4

C

2.29E+16

250.4

10.1

DE

1.88E+11

230.6*

7.7

F

1.93E+16

275.0

9.9

•*Pepper and Corvi (1995a) have deemed the default value of Emean =206.4 kJ/mol unreliable and unrealistic, thus the default is defined as 230.6 KJ/mol based on results calibrated to the reference solution.

 

 

Click to expand/collapseKerogen_gas_table    Kerogen gas table

Usage

Kerogen_gas_table

IDM=ival

JDM=jval

 

Real Values

 

 

 

 

where

ival

jval

Number of kerogen gas weights

Number of Rows in kerogen gas weight table (=2)

Description

Defines Kerogen->Gas table. The data is provided as a 2-D table where:

•Row 1 - List of Kerogen->Gas weights ( CKG (i))

•Row 2 - List activation energy ( Ei)

 

 

Click to expand/collapseKerogen_oil_properties    Defines the properties for Kerogen->Oil conversion via a Gaussian distribution

Usage

Kerogen_oil_properties

IDM=ival

 

 

Real Values

 

 

 

 

where

ival

Number of kerogen oil properties

Description

Defines the properties for Kerogen->Oil conversion via a Gaussian distribution. The values comprise:

•Location 1 - pre-multiplier ( A0)

•Location 2 - activation energy ( Emean)

•Location 3 - variance ( σ)

 

Notes

•Default parameters are available for specific named kerogen types:

Name

A0 (1/s)

Emean (KJ/mol)

σ (KJ/mol)

A

2.13E+13

206.4

8.2

B

8.14E+13

215.2

8.3

C

2.44E+14

221.4

3.9

DE

4.97E+14

228.2

7.9

F

1.23E+17

259.1

6.6

 

 

Click to expand/collapseKerogen_oil_table    Kerogen oil table

Usage

Kerogen_oil_table

IDM=ival

JDM=jval

 

Real Values

 

 

 

 

where

ival

jval

Number of kerogen oil weights

Number of Rows in kerogen oil weight table (=2)

Description

Defines Kerogen->Oil table. The data is provided as a 2-D table where:

•Row 1 - List of Kerogen->Oil weights ( CKO (i))

•Row 2 - List activation energy ( Ei)

 

 

Click to expand/collapseTOC    Total organic carbon by weight TOC

Usage

TOC

Real Value

 

 

Description

Defines the total organic carbon by weight ( TOC) in terms of the total organic carbon content in mass; i.e. the percentage of the mass of all carbon organic particles relative to the total mass of the rock matrix. It is therefore a concentration value of the generated and expelled petroleum masses using the total rock mass.

 

 

Click to expand/collapseTransformation_index    Transformation index TI (Also referred to as Transformation ratio TR)

Usage

Transformation_index

Real Value

 

 

Description

Defines Transformation index ( TI =S1/TOC) in SI units ( ghc /gc) as opposed to the often used units ( mghc /gc ).

 

 

Click to expand/collapseHydrocarbon_index    Initial hydrocarbon index (HI)

Usage

Hydrocarbon_index

Real Value

 

 

Description

Defines Hydrocarbon index ( HI =S2/TOC) in SI units ( ghc /gc) as opposed to the often used units ( mghc /gc ). Note that Transformation index TI is also referred to as Transformation ratio TR in the manual.

 

 

Click to expand/collapseGas_concentration    Gas concentration ratio

Usage

Gas_concentration

Real Value

 

 

Description

Defines the initial gas concentration ratio ( G ). Valid range is 0.0 < = G < = 1.0, where 0.0 corresponds to Oil-only generation and 1.0 corresponds to Gas-only generation. The gas concentration ratio differs from the often used expression ( GOGI ), but they are related (see Pepper and Corvi, 1995 Figure 2).

 

 

Click to expand/collapseReactive_content    Mass of reactive kerogen

Usage

Reactive_content

Real Value

 

 

Description

Mass of reactive kerogen CKR defines the initial mass of reactive kerogen terms of the percentage of the reactive mass of all carbon organic particles relative to the total mass of the rock matrix.

 

 

Click to expand/collapseWeight_fraction_carbon    The weight fraction of carbon in hydrocarbons W

Usage

Weight_fraction_carbon

Real Value

 

 

Description

W defines the weight fraction of carbon in hydrocarbons (Default 1.0 - corresponding to implicitly including W in S1 and S2).

 

 

Click to expand/collapseThickness    Thickness of kerogen layer

Usage

Thickness

Real Value

 

 

Description

Defines the thickness of kerogen layer. If Thickness is not defined, then the computed element volume will be used.

 

 

Click to expand/collapseKerogen_reaction_count    Kerogen reaction count

Usage

Kerogen_reaction_count

Integer Value

 

 

Description

Defines the number of parallel reactions in update procedure (Default =11).

 

 

Click to expand/collapseUniversal_gas_constant    Defines the universal gas constant R

Usage

Universal_gas_constant

Real Value

 

 

Description

Defines the universal gas constant R (Default: 0.00831446261815324 kJ/K/mol).

 

 

Click to expand/collapseKerogen_density    Defines the density of kerogen

Usage

Kerogen_density

Real Value

 

 

Description

Defines the density of kerogen (in the range of 1250 kg/m^3).

 

 

Click to expand/collapseHydrocarbon_density_model    Hydrocarbon density type

Usage

Hydrocarbon_density_model

Character Name

 

 

Description

Hydrocarbon_density_model defines the model for evaluation of the density of the expelled hydrocarbon; i.e. the average density of the expelled oil and liquid gas. Valid values are:

 

• "Constant" - Constant hydrocarbon density

 

 

Click to expand/collapseHydrocarbon_density_properties    Density of combined oil and liquid gas

Usage

Hydrocarbon_density_properties

IDM=ival

 

 

Real Values

 

 

 

 

where

ival

Number of density properties

Description

Hydrocarbon_density_properties defines density of expelled combined oil and liquid gas. The properties are dependent on the model type:

 

Constant

• Hydrocarbon density - Constant value for hydrocarbon density

 

Notes

•Default hydrocarbon densities are available for specific named kerogen types:

Name

Hydrocarbon density (kg/m^3)

A

898

B

865

C

876

DE

860

F

835

 

 

Click to expand/collapseKerogen_initialisation_flag    Defines whether groups assigned kerogen are initialised as kerogen present or not.

Usage

Kerogen_initialisation_flag

Integer Value

 

 

Description

Defines whether groups assigned kerogen are initialised as kerogen present or not. By default the kerogen is assigned to the complete group, whereas if set as off then kerogen must be assigned via spatial state initialisation. Valid values are:

•0 - kerogen is not present

•1 - kerogen is present (default)