Sandstone cementation and fluids in hydrocarbon basins

Are porewater flow or stasis exclusive hypotheses? We think there is an intermediate view. Processes governing sandstone cementation in the deep sub-surface are elusive, case-specific and difficult to model in general terms. Combining techniques from petrography, isotopic and ion microprobe analyses with basin modelling one can narrow the possibilities towards unique hypotheses. Examples are given, predominantly from the North Sea basins, where palaeo-porewaters in different settings may evidence: (1) meteoric, compaction, or convection origins; (2) overpressured vertical leakoff; and (3) stasis and >100 m 'diffusion', helped by flow dispersion. Geochemical interaction transfers K and Al to muds, C to sands and forms secondary porosity by feldspar loss at depth, late carbonates, and hairy illite that can date oil charge.