Numerical simulation of thermal convection in compacting sedimentary basins

SUMMARY A numerical model of combined fluid flow and heat flow is used to study convection in sedimentary basins during compaction. the main issue of the paper is the interaction of non‐Rayleigh convection flow with compaction flow and/or meteoric flow. It is shown that under reasonable assumptions, the flow inside a permeable layer is the superposition of the compaction flow through the layer and the thermal convection flow in the layer. These assumptions are expressed in terms of the time constants involved. Non‐Rayleigh convection roll(s) will therefore appear if the compaction flow (or the meteoric flow) is less than the thermally induced flow. This condition can be stated by a simple expression involving the Rayleigh number for the layer and the absolute value of the flow velocity through the layer. Two case studies are presented, which show non‐Rayleigh convection in compacting basins. A numerical example of Rayleigh convection is also presented, which demonstrates that Rayleigh convection, under realistic conditions such as compressible rock and non‐perfect thermal conducting top and bottom boundaries, is a complex process. This case study shows that even a ‘small’ amount of vertical excess pressure gradient is enough to stabilize the fluid inside a layer. sedimentary basins thermal convection