Laboratory evaluation methods of water saturation in shales

Abstract

The reservoir water content is one of the key parameters to following reliable hydrocarbon reserves estimation of low-permeable shale reservoirs with unconventional hydrocarbon reserves. The extensive review of applied direct and indirect laboratory methods for determining the water saturation in unconventional shale reservoirs is presented in this article. The essence, advantages, disadvantages and limitations of methods are described in detail. It was demonstrated that direct laboratory methods (retort method, Zaks, Dean–Stark) which were originally developed for traditional reservoir rocks, give results with an error of up to 50% for rocks samples of unconventional reservoirs. On the other hand the Evaporation Method specifically developed for low-permeable rocks takes less time and provides more accurate (error up to 6.8%) gravitational and bonded water determination moreover, it requires up to 5 times less rock material for analysis.