UBC Theses and Dissertations
The effect of steam injection on the electrical conductivity of sand and clay Butler, David Buchanan
To interpret electrical surveys used to monitor subsurface steam-injection projects, one needs to know whether steam zones are resistive or conductive relative to initial conditions. This can be determined through laboratory measurements of the effects of steam injection on the electrical conductivity of sand. Experiments presented in chapter 2 measured the combined effects of the salinity of the boiler feedwaters and the steam quality - the fraction of the injected flux that is vapour. The injection of low quality steam, boiled from a saline solution, into clean sand saturated with the same solution, 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 solutions, resulted in conductivity dropping first to a minimum, and then increasing to an equilibrium value similar to that seen in the low quality injection. This localized conductivity minimum became progressively less conductive with time, and travelled 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. This suggests that many steam injections will create steam zones with electrically resistive fronts, which can be used to track the steam. The effects of clay on the electrical conductivity of steam zones is further investigated in chapter 3. Experimental and numerical results indicate that clay-bearing steam zones can be electrically conductive relative to initial conditions, in part due to water saturations in the steam zones that are higher than those in comparably steam-flooded clean sands. However, it is still likely that high quality steam injections will result in resistive leading edges of the steam zones. In low quality steam injections, where dilution banks do not form around the front, it is more likely that steam zones are entirely conductive relative to initial conditions, particularly in fresh water environments.
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