High-Pressure Compaction Studies and Chemistry of Solutions Squeezed Out of Muds at Different Stages of Compaction: ABSTRACT

Abstract

Remaining moisture content (% dry basis) was determined for various clays (montmorillonite, hectorite, illite, kaolinite, dickite, halloysite), marine mud, and soil samples and plotted versus the logarithm of pressure (up to 500,000 psi.). The straight-line relation at pressures above 40-1,000 psi. (depending on type of clay) suggests that compaction is more or less a simple continuous process in the pressure range studied. The resistance to compression apparently increases with higher packing density and more strongly coalesced structures. Most of the water is squeezed out during a relatively short period of time (1-4 days), and equilibrium is reached after about 7-60 days (depending on type of clay). The calculated (from water loss) permeability of clay at high overburd n pressures (15,000-400,000 psi.) is in the order of 10-10-10-13 darcys, values characteristic of nearly impervious soils. Consequently, compaction appears not to be limited by low permeability, but rather by resistance to grain deformation. The salinity of squeezed-out solutions (using fresh marine mud, various types of clay, and sea water) progressively decreases with increase in overburden pressure. Consequently, mineralization of interstitial solutions in shale should be less than that of waters in associated sandstone. Reliable results in determining the chemistry of interstitial solutions of marine mud require that nearly all fluid be squeezed from each sample and require pressures in the 150,000-400,000 psi. range. Experiments concerning X-ray analysis of compacted clay for deciphering the magnitude of overburden pressure were inconclusive. End_of_Article - Last_Page 608------------