Low salinity waterflooding investigation using radioactive tracer in different sand pack configurations

Abstract

Waterflooding is a simple secondary oil retrieval method practiced worldwide to assist and improve oil recovery. Consequently, understanding the flow behavior of the injected water is essential to ensure an efficient waterflooding process. Nevertheless, literature on utilizing radiotracers to investigate fluid flow behavior in oil reservoirs is limited. The current study observed and compared horizontal and vertical fluid flows in simulated sandstone reservoirs. Low salinity water of 500 ppm sodium chloride solution was injected into vertically and horizontally sand-packed columns at a flow rate of 3.5 mL/min. Subsequently, technetium-99m radioisotopes with a half-life of six hours were injected into the columns as tracers. The residence time distribution for both setups fitted the perfect mixer in the series model. Nonetheless, the calculated sweep efficiency and overall oil recovery percentage were higher for the horizontal than the vertical configuration, demonstrating that gravitational forces affect the flow behavior of fluids in oil reservoirs.