Experimental investigation on sandstone sample disaggregation using a repetitive freezing and thawing technique

A repetitive freezing and thawing disaggregation technique, simplified as freezing technique, is des-cribed. The freezing technique is a new method for preparing clay suspension during the separation and enrichment of authigenic illites from reservoir sandstones. The disaggregating effects and the controlling factors have been investigated in detail using typical sandstone samples, and compared with a wet grinding technique, as a conventional disintegration method. Comparing with the wet grinding technique, the freezing technique has advantages and disadvantages. The freezing technique is more effective to avoid detrital potassium feldspar contamination. The obtained authigenic illite K-Ar ages are more reliable as void of detrital contamination. Sample disintegration time is mainly related to porosity and permeability and long disintegration timeframes can be a disadvantage for well cemented sandstone samples. The buried depth of the sandstone samples is the main controlling factor, as well as the shale content and organic content comprising coal seams or residual oil films or bitumen coatings. The experimental results show that the freezing technique can be used to disaggregate less consolidated or medium cemented sandstones mainly related to variable shallow to medium depths ranges. For well cemented and deeply buried sandstones with low porosity and permeability ranges, the method is less suited as long disintegration timeframes of several months or years are required. The experimental results also show that the wet grinding is still a practical and effective technique for preparing clay suspension, with the advantages of easy-operation, celerity and better effects, and has very bright application futures.