Experimental Investigation of the Influence of Nanoparticles Adsorption and Transport on Wettability Alteration for Oil Wet Berea Sandstone

摘要

Wettability alteration has been proposed as an important Enhanced Oil Recovery (EOR) mechanism for nanoparticles suspension. For better understanding nanoparticles adsorption behavior inside core and its effect on wettability, a series of wettability measurement experiments for oil wet Berea sandstone were conducted, where the core plugs were treated by different concentration and type of nanoparticles suspensions. Nanoparticles transport experiments also were performed for core plugs with injection of varying concentration and type of nanoparticles suspensions. Pressure drop across the core plug during injection was recorded to evaluate nanoparticles adsorption and retention inside core, as well as desorption during brine post-flush. Both hydrophilic silica nano-structure particles and hydrophilic silica colloidal nanoparticles were utilized in above two experiments. Contact angle between oil and nanofluids mea- surements also were performed to investigate the effect of nanoparticles on wettability. The results of wettability alteration experiments indicated that hydrophilic nanoparticles have ability of making oil wet Berea sandstone to be more water wet, and the higher concentration the more water wet will be. Different types of nanoparticles have different effect on the wettability alteration process. The results from contact angle measurements were consistent with wettability index measurements. For nanoparticles transport experiments, the results showed that the nanoparticles undergo both adsorption and desorption during injection. Pressure drop curves showed that absorption and retention of nano-structure particles inside core was significant, while colloidal nanoparticles did not adsorb much. Permeability impairment was observed during nano-structure particles fluid injection, but on the contrary colloidal nanoparticles dispersion injection made core more permeable.