Convective fluid flow and diagenetic patterns in domed sheets

Abstract

When a moving pore fluid maintains equilibrium with the host rock, the flow and temperature fields can combine to produce diagenetic patterns. These diagenetic patterns define source and sink regions for mass transfer within the rock and permit prediction of both the spatial distribution of diagenetic alteration and its intensity. Analytical solutions have been obtained for the fluid flow and temperature fields for the case of a folded porous layer embedded in an impermeable medium heated from below and held at a constant temperature above. This corresponds to a layered sequence of rocks in which a permeable sand is bounded above and below by impermeable shales. The present results are limited to gently folded strata (small dip angles) but are quite general with regard to the actual layer geometry. The solutions depend on the fact that the temperature field can be uncoupled from the fluid flow when convection is weak. This results in a purely conductive temperature field which drives the fluid motion through buoyancy effects. It is shown that the dynamic of the system are most strongly influenced by the geometry of the porous layer and the ratio of thermal conductivities of the rocks.