We measured Mercury Injection Capillary Pressure (MICP) profiles on tight shale samples with a variety of sample sizes. The goal was to optimize the rock preparation and data reduction workflow for determining the storage properties of the rock, particularly porosity, from MICP measurements. The rock material was taken from a whole core in the Cretaceous Eagle Ford Formation in the form of a puck or disc. A horizontal 1 inch core plug was cut from this disc and the remaining material was subsequently crushed and sieved through various mesh sizes. MICP profiles up to 60,000 psia were then measured on the 1 inch plug and all of the various crushed and sieved rock particle sizes. In parallel we subsampled the plug material to measure bulk volume, grain volume, and porosity using a crushed rock helium pycnometry method. These additional measurements provided a comparison set of standard petrophysical properties from which we could compare the MICP results. In general our MICP profiles show a very strong dependence on sample size due to two reasons: pore accessibility and conformance. We verify the conformance correction approach of Bailey (2009) which specifically accounts for the pore volume compression of the sample before mercury has been injected into the largest set of interconnected pore throats. This new method is preferred over the traditional method of conformance correction when compared to crushed rock helium porosity since the latter is performed at unstressed conditions. Our results using Bailey’s (2009) method reveals that the -20+35 sample size is optimal for determining porosity in the Eagle Ford, and potentially other tight oil and gas shales. We use mercury injection for determining the various storage properties of tight shale because helium porosimetry is not always possible on fine cuttings samples. There are many instances when limited cuttings may be the only source of rock information available before a whole core is taken. Cuttings profiles also provide a key insight over long formation intervals that may not be available from whole core. Cuttings and core profiles for use in calibrating well logs have proven to be a requirement in these ultra-low perm systems.

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Tensiometers sense the chemical potential of water (or water potential, Ψw) in an external phase of interest by measuring the pressure in an internal volume of liquid water in equilibrium with that phase. For sub-saturated phases, the internal pressure is below atmospheric and frequently negative; the liquid is under tension. Here, we present the initial characterization of a new tensiometer based on a microelectromechanical pressure sensor and a nanoporous membrane. We explain the mechanism of operation, fabrication, and calibration of this device. We show that these microtensiometers operate stably out to water potentials below -10 MPa, a tenfold extension of the range of current tensiometers. Finally, we present use of the device to perform an accurate measurement of the equation of state of liquid water at pressures down to -14 MPa. We conclude with a discussion of outstanding design considerations, and of the opportunities opened by the extended range of stability and the small form factor in sensing applications, and in fundamental studies of the thermodynamic properties of water.

In perfusion experiments, the hydraulic conductance of stem segments (K xylem ) responds to changes in the properties of the perfusate, such as the ionic strength (I c ), pH, and cationic identity. We review the experimental and theoretical work on this phenomenon. We then proceed to explore the hypothesis that electrokinetic effects in the bordered pit membrane (BPM) contribute to this response. In particular, we develop a model based on electroviscosity in which hydraulic conductance of an electrically charged porous membrane varies with the properties of the electrolyte. We use standard electrokinetic theory, coupled with measurements of electrokinetic properties of plant materials from the literature, to determine how the conductance of BPMs, and therefore K xylem , may change due to electroviscosity. We predict a nonmonotonic variation of K xylem with I c with a maximum reduction of 18%. We explore how this reduction depends on the characteristics of the sap and features of the BPM, such as pore size, density of chargeable sites, and their dissociation constant. Our predictions are consistent with changes in K xylem observed for physiological values of sap I c and pH. We conclude that electroviscosity is likely responsible, at least partially, for the electrolyte dependence of conductance through pits and that electroviscosity may be strong enough to play an important role in other transport processes in xylem. We conclude by proposing experiments to differentiate the impact of electroviscosity on K xylem from that of other proposed mechanisms.

Greige cotton contains waxes and pectin on the outer surface of the fiber that are removed when bleached, but these components present potential wound dressing functionality. Cotton nonwovens blended with hydrophobic and hydrophilic fibers including viscose, polyester, and polypropylene were assessed for clotting activity with thromboelastography (TEG) and thrombin production. Clotting was evaluated based on TEG measurements: R (time to initiation of clot formation), K (time from end of R to a 20 mm clot), α (rate of clot formation according to the angle tangent to the curve as K is reached), and MA (clot strength). TEG values correlate to material surface polarity as measured with electrokinetic parameters (ζplateau, Δζ and swell ratio). The material surface polarity (ζplateau) varied from −22 to −61 mV. K values and thrombin concentrations were found to be inversely proportional to ζplateau with an increase in material hydrophobicity. An increase in the swell ratios of the materials correlated with decreased K values suggesting that clotting rates following fibrin formation increase with increasing material surface area due to swelling. Clot strength (MA) also increased with material hydrophobicity. Structure/function implications from the observed clotting physiology induced by the materials are discussed.