Electrokinetic and Chemical Aspects of Transport of Chloride Brines Through Compacted Smectite Layers at Elevated Pressures (Electroosmosis, Streaming, Conductivity)

216 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.Solutions of NaCl and NaCl-CaCl were forced through clay plugs made by compacting the 0.2 to 2.0 micron size fraction of Cheto montmorillonite. The concentration of NaCl solution was either 1.10 m or 1.087 m, and that of NaCl-CaCl(,2) solution was 0.92 m in NaCl and 0.075 m in CaCl(,2). Clay plug thicknesses ranged from 0.32 to 0.5 centimeters. The clay plugs were prepared differently in order to obtain different fabrics. Six experiments were carried out. It took five to ten weeks to achieve constancy of effluent chemical composition and of streaming potential. Confining pressure (CP) in these room temperature experiments was 5000 pounds per square inch (psi), differential hydraulic pressure (DHP) across the clay was 2000 psi, and mean hydraulic pressure (MHP) was 2300 psi. These values of CP and MHP are approximate for a depth of 5000 feet in sedimentary basins.Hydraulic flow rate, electrical conductance, streaming potential, electroosmotic flow rate and brine chemical composition were measured periodically until steady state. At steady state, stable oxygen isotopic compositions of both input and effluent reservoirs were determined for three runs and approximate osmotic flow rates were determined for two runs.The presence of Ca('2+) in the brine resulted in lower hydraulic conductivity and streaming potential but slightly higher electrical conductivity. The electroviscous effect was shown to cause a significant reduction in the flow rate. The experimental results conform to the predictions of nonequilibrium thermodynamics, for both Na-Cl and Na-Ca-Cl systems, under these simulated subsurface conditions. It appears from the data produced that osmotic and electroosmotic effects may be responsible in driving large amount of cross-formational subsurface fluid flow. Salt filtration efficiencies (SFE) from 27 to 48% and oxygen isotopic enrichments of -0.25 to -0.63% (SMOW) were measured. SFE increased with decreasing hydraulic flow rate. In the Na-Ca-Cl system, Na('+) was preferentially transported through the clay relative to Ca('2+).U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD