CAPILLARY FLOW POROMETRY – ASSESSMENT OF AN ALTERNATIVE METHOD FOR THE DETERMINATION OF FLOW RELEVANT PARAMETERS OF POROUS ROCKS

摘要

The determination of flow relevant parameters of porous rocks(e.g.permeability,pore throat radii distribution,pore size distribution,porosity,to name only few) forms since decades a well established part of petrophysics to characterize,understand and assess reservoir rocks in terms of their hydraulic properties and flow behavior.For the determination of the pore throat radii/pore size distribution of porous rocks,the mercury injection technique(after Purcell) is commonly used.With this technique,the rock sample is flooded with mercury,whereat the applied injection pressure is proportional to the size of the pores(pore throats),which are through-flown.Nevertheless,this technique is not only time consuming(several hours),the sample is strongly mechanically influenced,due to the high overburden/injection pressure(up to 10,000 psi) and additionally,it is contaminated with mercury.Contaminated rock samples are very difficult to handle,toxic and,in most cases,the valuable core sample is lost for further investigations.The authors would like to present a promising alternative to this well established method,the so called Capillary Flow Porometry(CFP).Originally developed for the characterization of filter papers,porous membranes and other nanostructure materials,this technique has been successfully adapted for petrophysical purposes by a first prototype.Contrary to Hg-injection,CFP uses an inert gas(e.g.nitrogen) to push a wetting and nontoxic liquid out of the porous network,where the applied pressure is again inversely proportional to the corresponding pore/pore throat.Furthermore, measuring time is greatly reduced from several hours to several minutes.First measurements on different cretaceous sandstones show good reproducibility and good accordance to Hg-injection experiments.Additional core and special core analyses(CAL /SCAL) have been carried out(permeability,BET surface,porosity,NMR,μ-CT),to characterize the corresponding porous networks as complete as possible,and to correlate results of the Hg-injection and CFP meaningful.