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Modeling source rock distribution, thermal maturation, petroleum retention and expulsion: The Case of the Western Canadian Sedimentary Basin (WCSB) Stanislas
1 Pauthier ,
Mathieu 1 IFP
1 Ducros ,
Benoit
1 Chauveau ,
Tristan
2 Euzen ,
William
1 Sassi
Énergies nouvelles, Geosciences Division, Rueil Malmaison, France 2 IFP Technologies (Canada) Inc., Calgary, AB, Canada. Contact:
[email protected]
Introduction Basin modeling is a multi-disciplinary approach integrating varied sources of geological data. Therefore, the main objective is to build models consistent with the available information. For instance, input parameters such as heat flow and initial TOC must be first calibrated at the location of wells and extrapolated on maps taking into account available geological, biological or geochemical concepts.
We present solutions that allow to produce calibrated and geologically meaningful maps of heat flow, initial TOC and hydrogen index based on both well measurements and on the geological information included in the basin model. They are applied on a large scale basin model of the WCSB (800km x 1300km) using TemisFlow® (Fig. 1). A focus is done on the Montney and Nordegg source rocks intervals and on the unconventional petroleum system of the Montney Formation.
Fig. 1: 3D model of the Western Canadian Sedimentary Basin. (34 stratigraphic units with a 5km cell resolution).
Fig. 2: Location of the simulated 3D and 2D models in the Western Canadian Sedimentary Basin
Geological settings of the WCSB Foreland basin limited to the East by the Precambrian Canadian Shield and to the West by the Canadian Cordillera (Fig. 2). 3 major periods: Paleozoic to early Mesozoic time: sedimentation on the western margin of a stable craton dominated by carbonate deposits. Jurassic to Paleocene: clastic sedimentary wedge induced by the formation of the Cordillera and its associated foreland basin. From Paleocene onward: Erosion and sediment by-pass (Laramide Orogeny). Focus on Montney and Doig Formations (Fig. 3): Siliciclastic sediments of the Triassic succession. They rest unconformably on the Permian Belloy Formation. The Upper boundary of the Triassic is a major unconformity related to the formation of the Canadian Cordillera. In the Eastern part, they are capped by the organic-rich shale of the Nordegg Formation. In the Western part, they are overlaid by the proximal sandy deposits of the Middle Triassic Halfway Formation.
TOC0,HI0
Fig. 3: Cross section presenting the main stratigraphic intervals of the WCSB.
Methodology and modeling workflow
Petroleum retention (organic porosity, adsorption) and expulsion
© 2012 - IFP Energies nouvelles
Geological 4D model (facies, bathymetry, thickness and sedimentation rate, well data, …)
Source rock maturity
Pressure , migration and HC alteration
Conventional and unconventional petroleum systems analysis
Uncertainty and risk
Renewable energies | Eco-friendly production | Innovative transport | Eco-efficient processes | Sustainable resources
Source rock richness at basin scale Chemical and biological conditions (Ox0, PP0)
Very prolific basin
PP0: Ox0:
Duvernay (Devonian, Type II) Exshaw-Bakken (Devonian, Type II Montney (Triassic, Type II) Phosphatic Doig (Triassic, Type IIS) Nordegg-Gordondale (Jurassic, Type IIS) Poker Chip (Jurassic, Type II) Mannville Coals (Cretaceous, Type III)
Simulation of TOC0 and HI0 at wells locations (TOC0S, HI0S) = function( sedimentation rate bathymetry biological conditions chemical conditions ) Optimization of (Ox0, PP0)
Sedimentation rate and bathymetry
HIOs
TOCOC
Estimation of initial SR potential Estimation of initial TOC (TOC0) and HI (HI0) maps of marine organic matters is performed based on geological and biological considerations (Fig. 5). Inputs: Modern TOC and HI measured at wells Paleobathymetry Sedimentation rate. Outputs: Estimated TOC0 and HI0 at well locations. Maps of TOC0 and HI0 at basin scale.
TOCPD: HIPD: TOCOS: HIOS: TOCOC:
primary productivity basin scale redox conditions present day TOC present day HI simulated initial TOC simulated initial HI computed initial TOC
Computation of TOC0C
TOCPD and HIPD
TOCOC
Computation of the error function Error = function(TOC0S – TOC0S)
Optimized (PP0, Ox0)
Sedimentation rate and bathymetry maps
Computation SR distribution and richness at basin scale
Fig. 4: Estimation of TOC0 and HI0 maps consists in two main steps: • An optimization of the biological (PP0) and chemical conditions (Ox0) using well data. • An extrapolation to basin scale based on the maps of bathymetry, and sedimentation rate and on the optimized PP0 and Ox0.
Fig. 5: Forward model for estimation of TOC0 and HI0 of from marine organic matter (MOM) as a result of primary productivity (PP0) and degradation processes. Degradation along the water column is estimated from Martin’s law (1987): the effective organic flux of organic matter (PPz) at the water/sediments interface is a function of the bathymetry and of the primary productivity (PP0). Finally, early diagenesis is estimated from the burial efficiency (i.e. sedimentation rate and redox conditions, Burdige , 2007)
Montney Formation
Focusing on the Montney and Nordegg Formations
• Type II (low TOC and oxic conditions) • Calibration from 7 wells
Bathymetry (m)
Nordegg Formation
Sedimentation rate (m/My)
HI0 (mgHC/gC)
• Type II/IIS (high TOC and anoxic conditions) • Calibration from 34 wells
Fig. 6: Geological settings associated to the deposition of the Nordegg and Montney organic-rich Formations. The Montney Formation exhibits, relatively to source rocks, high sedimentation rates (from 20m/My to more than 60m/My, top left) whereas low sedimentation rates (
