"Basin modelling" is used during hydrocabron exploration to predict HC-accumulations within a sedimentary basin.
Nonetheless, this tool is very useful in solving scientific problems. Detailed background information is available from 
the DGSI page. I am using the PetroMod 2D/3D software suite of IES GmbH, Jülich.

Example:

Modelling deep basin gas accumulations in 3D -
an example  from the Alberta Deep Basin

C. Büker ^1,2, A. Fröhlich ², C. Zwach ³ & H.S. Poelchau ⁴

1 Institute of Geology and Geochemistry of Petroleum and Coal, Aachen University of Technology, D-52056 Aachen, Germany (bueker@lek.rwth-aachen.de)
2 Integrated Exploration Systems (IES) GmbH, D-52428 Jülich, Germany (carsten@ies.de)
3 Norsk Hydro AS, N-1320 Stabekk, Norway 
4 Institute of Chemistry and Dynamics of the Geosphere 4 (ICG-4), Forschungszentrum Jülich, D-52425 Jülich, Germany
 

The Alberta Deep Basin (Fig. 1) contains an unconventional gas trap where water saturated rocks overlie an almost gas 
saturated, thick sedimentary section of Lower Cretaceous age. The gas most probably originated from the adjacent coal 
bearing Upper Jurassic and Lower Cretaceous sequence. The reservoir and source rock distribution in the area is well 
known due to extensive drilling, but the processes involved in gas accumulation and preservation are still poorly under- 
stood. Three main theories in the literature attempt to explain the present day occurrence of gas in the Alberta Deep Basin:

i) the on-going gas generation in source rocks at present day due to very high heat flow (Maubeuge & Lerche, 1993),
ii) the desorption of the gas from the coal source rocks due to uplift (Wyman, 1984), and 
iii) trapping due to permeability boundaries formed by diagenesis (Masters, 1979).
 

Figure 1
Left: Map of the Western Canada Sedimentary Basin showing the isopachs of the sedimentary fill (in kilometres), some 
important tectonic elements of the Alberta and the Williston Basin, and the five Cordilleran tectonostratigraphic belts 
of Western Canada. The study area is located in the north-western part of the Alberta Deep Basin. 
Right: Structure of the Alberta Deep Basin. Cretaceous formations (Cadomin and younger) are gently dipping towards 
the southwest .

To get a better understanding of how the gas accumulations formed and why they still exist, 2D (Zwach, 1995) and a new 
3D basin modeling system were used. The regional erosion and heat flow history was constrained using a detailed analysis
of acoustic velocities of shales (Fig. 2), and vitrinite reflectance and fluid inclusion data, respectively. The geometry of the 
numerical models (Fig. 3; Tab. 1) was constructed using bore-hole data from a large database of some 1700 wells (Poelchau & 
Zwach, 1993). For modeling the generation of methane from coals, a specific kinetic data set (Krooss et al., 1993) was used.
Some modelling results are shown in figures 4 and 5.

Figure 2
Left: Magara´s sonic method of estimating thickness of eroded sediments (after Magara, 1986). 
Right: Regional estimated amount of eroded overburden after Poelchau & Zwach (1993). Open circels indicate boreholes
on which Magara´s method (left) was applied. Included are the locations of cross sections (red lines) and the area (red 
frame) for which 2D (Zwach, 1995) and 3D basin modeling was carried out, respectively. Note the gas-water contact 
indicating that water saturated rocks in the shallow northeastern part overly gas saturated rocks in the deeper south-
western part of the basin.
 

Figure 4
Burial history for the central grid cell and heat flow history used in the Finite-Element model.
 
 
 

Table 1 Basic input data for the Finite-Element model.  Nikanassin, Bluesky-Gething and Falher contain the  main source rocks and the Cadotte sandstone is the most important reservoir rock.

Figure 5 Modeled methane accumulation history. Overlay colors indicate  the saturation of the pore space with methane (in percent).View is  on top of Cadotte (layer 16 in Tab. 1). All layer on top of Cadotte  are hidden. The uppermost, blue outlined layer is the today eroded Paskapo-Wapiti (layer 26 in Tab. 1), its upper limit is the earth  surface.

Conclusions

i) The Alberta Deep Basin was inverted during the Tertiary, and significant amounts of Late Cretaceous and Early Tertiary 
deposits were eroded.

ii) Methane generation in the Late Jurassic and Early Cretaceous source rocks (coals) was mainly controlled by the depo-
sition of the later eroded Late Cretaceous and Early Tertiary sequence.

iii) An on-going gas generation in the source rocks at present-day due to very high heat flow can be ruled out.

iv) The present-day gas saturation in the Early Cretaceous sequence arises most likely from a combined effect of diagenetic
trapping and desorption of gas from coals due to Tertiary uplift and erosion as pore pressure and temperature decrease.

References

Krooss et al. (1993), Erdöl und Kohle - Erdgas -Petrochemie, 46 7/8: 271-276
Magara (1986),  Collection Colloques et Séminaires, IFP, 44: 129-147
Masters (1979), AAPG Bulletin, 63/2: 152-181
Maubeuge & Lerche (1993), Energy, Exploration & Exploitation, 11/3+4: 357-388
Poelchau & Zwach (1994), Reports Research Centre Jülich, 2882: 1-142 (B1); ISSN 0944-2952
Wyman (1984), AAPG Memoirs, 38: 173-187;
Zwach (1995), Reports Research Centre Jülich, 3082; ISSN 0944-2952.

Support of Canadian Hunter Exploration Ltd., Calgary, the German Ministry of Research and Technology 
(BMFT, project No. ET6906A4) and the Research Center Jülich is is gratefully acknowledged.