Quantification of heat and fluid flow through time by 3D modeling : an example from the Jeanne d'Arc basin, offshore eastern Canada

Demand for energy is growing rapidly, causing worldwide concerns on security of supply. Petroleum systems modeling in 4 dimensions (cube + time) predicts generation, migration, and quality/quantity of accumulated hydrocarbons in reservoirs, incorporating temperature and pressure through the entire evolution of the basin. A petroleum systems model thus provides the only means to combine all physical aspects (source, trap, seal, and reservoir) and timing (charge) to reduce exploration risk and provide a reasonable resource assessment to guarantee a secure and constant supply of hydrocarbons. Over the years, the technology has advanced so far that the basin model results in combination with multi phase chemical reaction kinetics appear to approach reality. Nobody has quantified and published how close to reality these models actually get in the Jeanne d’Arc basin, especially in terms of charge history reconstruction and fluid quality and quantity. All necessary input data for a numerical model are available: especially for the Kimmeridgian Egret Member, the only mature source rock, which generates hydrocarbons; pvT (pressure, volume, temperature) data; and source and reservoir samples are accessible for more than 50 wells. Furthermore, there is processed, converted and interpreted 3D seismic available for the Jeanne d’Arc Basin. This makes the basin ideal for the present study. In addition, petroleum systems modeling should itself be tested to constrain correct assumptions and routines, as well as to improve the predictive capacity of the basin modeling approach. The first part of the thesis focused on the reconstruction of the geodynamic situation of the basin yielding new results for the reconstructed heat flow history using a 3D enhanced McKenzie model. Results show that to understand the thermal evolution of the Jeanne d’Arc sedimentary basin completely, it is crucial to consider the Triassic rift system. This first rift generated the structural framework of the basin, where most of the sediments were deposited. A second extension, in the Cretaceous, represents most likely an ultra-slow extension phase with a heat-impulse, too weak to leave any thermal record. This study demonstrates that the entire evolution of the Jeanne d’Arc basin can be reconstructed assuming just one single Triassic thermal rift. Additionally, the study shows the theoretical effects of lateral heat transfer on the determination of McKenzie stretching factors, its resulting implications for the tectonic subsidence, and the reconstructed heat flow history. The second and third parts concentrate on the determination of source rock properties (chemical reaction kinetics – bulk, multi component and PhaseKinetics) and on the reconstruction of the petroleum reservoir filling history for the entire basin. Petroleum generation and phase behavior were analyzed using phase-predictive compositional kinetic models (PhaseKinetics) determined by pyrolysis of Egret Member source rock samples. Different charge scenarios were tested to reconstruct the most likely migration pathways for the petroleum, which is trapped in the Terra Nova oil field. The most probable filling history includes charge to the reservoir from a local kitchen and a second kitchen located between Hibernia and Terra Nova that was responsible for the long-range contribution. This new migration concept differs from the traditional explanation based on geochemical measurements only (published by von der Dick et al., 1989), which infers that local generation was solely responsible for filling the Terra Nova field. This theory of local generation can be disproved based on a simple mass balance calculation. The mass of the local source rock is not enough to generate the known present amount of hydrocarbons. Finally, the study presents a basin-wide mass balance calculation showing the impact of a newly tested adsorption behavior of the source rock. Additionally, this chapter discusses the influence of different migration techniques (flowpath, Darcy, hybrid and invasion percolation) on a basin-wide mass balance calculation (MBC) in the Jeanne d’Arc basin. It can be concluded that a pure Darcy migration is not sufficient to reproduce the accumulation pattern in the basin and that hybrid or flowpath are the most efficient and precise migration methods to predict correct volumes and composition. Additionally, it turned out that the applied adsorption model does not adequately reproduce the natural behavior of source rocks (SR). Therefore, a revised approach was applied, in which the adsorption capacity is in general much higher, but diminishes, with increasing maturity. In summary, the study provides new insights into the geodynamic development of the Jeanne d’Arc basin, presents calibrated, verified and tested kinetics for the Egret source rock and presents new aspects of a mass balance calculation for the entire basin.

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