Streaming potential properties of westerly granite with applications

Abstract

This paper reports on laboratory measurements of the streaming potential properties of common minerals and in particular of Westerly granite. Data are presented for these solids in contact with simple electrolytic solutions and in one case for temperature variation in the range 5°–70°C. For 1:1 electrolytes the ratio of the streaming potential coupling coefficient to fluid resistivity was approximately −4 mV/(atm Ωm) and for 2:1 electrolytes −2 mV/(atm Ωm). The effect of temperature was small (0.05 mV/°C temperature increase) and indicates that the zeta potential was independent of temperature. Preliminary experimental results using mixed electrolytic solutions (NaCl + CaCl2) and two‐phase fluid flow are also described. Two‐phase flow can enhance streaming potentials by as much as a factor of 3 or 4. The laboratory data are used to interpret streaming potentials in geological problems, such as earthquake prediction, geothermal prospecting using the self‐potential method, and surface conductivity contribution to the electrical resistivity of rocks.

Determination of rock properties by low‐frequency AC electrokinetics

“…If these cavities are closed, the mass transfer creates a compression in one cavity and a decompression in the other, thereby generating an electroosmotic pressure AP. As with streaming potential, the steady state electroosmotic pressure is linearly proportional to the applied voltage, and the proportionality constant is denoted [Amaefule et al, 1986], the onset of inertial (i.e., "turbulent") effects at high flow rates [Geertsma, 1974], or not having adequate time for the steady state fluid flow profile to become fully established in low-permeability samples [Morgan et al, 1989]. If the sample under test has a rigid structure and permeability that is not too low, linearity in Ks can persist with applied pressures as large as 100 kPa and perhaps higher [Ishido and Mizutani, 1981; Jouniaux and Pozzi, 1995].…”

Vertical seismoelectric profiling in a borehole penetrating glaciofluvial sediments

“…[22] The z potential for most water-saturated geological sediments, according to Ishido and Mizutani [1981] and Morgan et al [1989], ranges between À10 mV and À100 mV; we choose À50 mV as an intermediate value.…”

Experimental studies of seismoelectric conversions in fluid‐saturated porous media

“…The induced field is simply a sta1Now at Shell UK Exploration and Production, Aberdeen, Laboratory experiments have been performed to measure streaming potentials caused by a pressure gradient through a porous rock and to determine the zeta potential or enhanced conductivity through the electrical double layer along the grain surfaces [Morgan et al, 1989;Jouniaux and Pozzi, 1995]. Zhu et al [1999] investigated the electrokinetic conversions in fluid-saturated borehole models.…”