Mathieu Ducros

2-D Basin Modeling of the Western Canada Sedimentary Basin across the Montney-Doig System: Implications for Hydrocarbon Migration Pathways and Unconventional Resources Potential

Abstract Basin and petroleum system modeling tools can aid in assessing unconventional resources. The present study gives an overview of the petroleum system of the Western Canada Sedimentary Basin (WCSB) through the modeling of a representative regional geologic cross section. A special emphasis is given on the Triassic Montney and Doig formations, which host the largest known unconventional play in Canada. Our model simulated the large diversity of plays that are found in the WCSB: self-sourced and tight reservoirs as well as conventional reservoirs with conventional and biodegraded oils. Results of this study strengthen the hypothesis of long-distance (>100 km [>62 mi]) migration for a major part of the hydrocarbons generated by the Gordondale and Doig Phosphate source rocks from the western to the eastern part of the basin. They also show that hydrocarbons generated within the Montney formation did not migrate far from their source rock due to very low permeabilities. Although the quantification of expelled versus generated hydrocarbons is still in its infancy, our results suggest that as much as half of the hydrocarbons generated in the Montney-Doig formations might still be retained in their source rock. Extending such a model in three dimensions might help improving the assessment of the volumes and distributions of dry gas, liquid-rich gas, and oil present in the low-permeability Montney and Doig formations.

Probability maps of reservoir presence and sensitivity analysis in stratigraphic forward modeling

One of the main objectives of petroleum exploration consists of predicting reservoir location. Data collected in the basin are used to better understand the sedimentary architecture but are usually insufficient to accurately characterize this architecture. Three-dimensional stratigraphic forward modeling has brought new insights in the understanding of sediment distribution. It gives the opportunity to investigate several geological models and to tackle reservoir presence probability. However, simulation time is a strong limitation to properly taking the uncertainties into account during operational studies. Here, we propose a methodology based on metamodels (or surrogate models) to perform sensitivity and risk analyses. The objective is to reduce the simulation time necessary to quantify the regional impact of the input parameters and to estimate probability maps of reservoir presence. The approach consists of building functions that approximate the spatial outputs of the simulator (such as sediment thickness or net-to-gross distributions in the basin) and that are fast to evaluate. These functions are then called instead of the stratigraphic forward simulator for uncertainty quantification. The proposed methodology is applied to a three-dimensional synthetic case study, considering uncertainty on input parameters related to sediment transport, accommodation space, and sediment supply. The sensitivity analysis quantifies in each location the influence of the parameters on the sediment distribution, which can help to better understand the influence of each uncertain process on the basin architecture. In addition, probability maps of reservoir presence are estimated. The proposed approach is a promising trade-off between simulation time and information that can be inferred.