Overpressure on eclipse

[MACH2009]

Hi every body
it s my 1 st time i participate in this helpfull forum
i would like to ask if any one know how to integrate the overpressure effect on the pressure depletion profile on an eclipse data file
i tried some keywords about rock compaction but it dosen't work
the great ECLIPSE "dont know" what is an overpressurized reservoir

thanks

[vinomarky]

Can you elaborate exactly the scenario you are trying to simulate in Eclipse?

Overpressure..... I assume you mean differentially pressured in different areas of the reservoir? If they are all the same (overpressured) pressure, then simply using ROCKTAB keyword family should handle pressure support due to compaction

[MACH2009]

it's a tight gas reservoir which has an abnormal high initialy pressure(130 – 180% hydrostatic) due to stratigaraphic sealing or other structurale configuration.
during the depletion and at approximately normal pressure gradient, the formation compaction is essentially complete and the reservoir assumes the
characteristics of a normal gas expansion reservoir. This lead for a
second slope on the pressure decline.
i want to simulate this decline on eclipse

thank you for your help

[vinomarky]

Firstly, you'll probably get a wider audience willing to help on the spe.org site. Having said that, here are my thoughts

This seems like a (relatively) standard application of rock compaction

Enable it in Eclipse with ROCKCOMP keyword in your RUNSPEC, then define the pressure dependent PV and TRANS multipliers in the PROPS section with ROCKTAB keyword

In your case I would assume that for PV you'd have two distinct trends. One above 'normal' gradient (either a history match parameter, of from some sort of SCAL test), and one below the 'normal' gradient that corresponds more to standard consolidated rock compressibility type factor

I would guess TRANS multipliers probably correspond more to a lognormal relationship as your porosity decreases - especially above the normal pressure

Good luck