A Molecular Dynamics Study of Primary Production from Shale Organic Pores

F Perez and D Devegowda, SPE JOURNAL, 25, 2521-2533 (2020).

We created a model of mature kerogen saturated with a black oil. Our fluid model spans light, intermediate, and long allcane chains; and aromatics, asphaltenes, and resins. The maximum pore diameter of our kerogen model is 2.5 nm. The insertion of a microfracture in the system allows us to study fluid transport from kerogen to the microfracture, which is the rate-limiting step in hydrocarbon production from shales. Our results indicate that the composition of the produced fluids changes with time, transitioning from a dry/wet gas to a gas condensate, becoming heavier with time. However, at any given time, the produced fluid is significantly lighter than the in-situ fluid. The species with the greatest mobility is methane, which is expected because it is the lightest molecule in the fluid and its ability to migrate is greater than that of all other fluid molecules. A sensitivity analysis shows that the produced fluid composition strongly depends on the initial composition of the fluids in organic pores.

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