The effect of steam quality on the electrical behavior of steam-flooded sands: A laboratory study

Laboratory measurements of the effects of steam injection on the electrical conductivity of sands can aid in the interpretation of electrical surveys used to monitor subsurface steam-injection projects. The effect of variations in injected steam quality was measured in the experiments presented here. The injection of low-quality steam, boiled from a 0.01 mol/L NaCl solution, into clean sand saturated with 0.01 mol/L NaCl, resulted in a net decrease in conductivity and a constant equilibrium conductivity in the steam zone, The injection of high-quality steam, using the same saturating and injection salinities, caused the conductivity to first drop to a minimum and then to increase to an equilibrium value similar to that seen in the lowquality injection. The local conductivity minimum deepened with time and traveled with the steam front. The appearance of the conductivity minimum at the steam front can be attributed to the formation of a dilution bank, which temporarily decreases the local salinity. The extent of the dilution increases with time, resulting in the decrease of the conductivity over time. The conductivity then increases as injected salt moves through the sand. The steam quality controls the appearance of this minimum because it determines the relative speeds of the steam front and the steam liquid: a minimum will not occur if the steam front moves more slowly than the steam liquid.