Mass transfer and gelation in sandstone cores of a novel water shut off chemical

An innovative water shut-off chemicals was recently proposed. The chemical is soluble in oil without any chemical reaction and forms gel in the presence of water. When the chemical dissolved in oil is injected in the near well-bore formation it modifies selectively the two-phase flow properties in order to reduce the production of water. The gelation process involves the partitioning of the chemical from the oil phase into the water phase. Upon contact with water a heterogeneous (hydrolysis and condensation) reaction takes place between gelant and water, leading to the formation of a gel in the water phase. Recently we have demonstrated that NMR imaging is a viable technique for visualizing and quantifying the above reactive mass transfer process in bulk and glass bead systems. ^1,2 Here we report a new core-flood experimental study consisting of the placement of the chemical dissolved in oil in Bentheim sandstone cores. NMR imaging and (T ₁ and T ₂) relaxation time measurements are used to monitor the reactive transport of the chemical in the core. The mass transfer of the chemical from the oil phase to the water phase is derived from the measurement of T ₁ related to the oil phase. The progress of hydrolysis and gelation is indicated by a decrease in T ₂ of the water phase.