Modeling secondary migration and accumulation of hydrocarbons is one of the principal requirements in multi-dimensional basin simulation. In this paper, the treatment of secondary migration on basin simulators was discussed from both numerical and experimental point of view.
Firstly, a new gridding method is proposed for increasing reproductivity by decreasing discretization errors, in which thin grids in both source/seal bed and carrier bed along their lithologic boundaries are constructed. Case studies using an imaginary siliciclastic sedimentary basin show that this treatment can reproduce secondary migration pattern that is close and consistent with those obtained from thinly divided grid systems without increasing cpu times and memory spaces. This treatment is also easily included into most of the previously developed basin simulators, thus, it would be an effective tool for modeling secondary migration in sedimentary basins.
Secondly, displacement patterns are discussed based on the relative magnitudes among buoyancy, interfacial, and viscous forces using the results of one-dimensional vertical oil-water displacement experiments. Two displacement patterns are recognized during the experiments, one clearly formed a typical shock front and the other did not. Through trial-and-error matching approach using a two-phase fluid flow simulator, we found that the “shock-front” pattern can be reproduced by using typical relative permeability curves, while for “non-shock-front” case, we need quite different curves to reproduce observed results. It suggests that ordinary relative permeability curves obtained from special core analysis in the field of reservoir engineering might not be valid for modeling secondary migration.
Such investigations would be important for improving our understanding of petroleum migration in sedimentary basins, and should be conducted in parallel with the application of simulators to actual basins.
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