Water injection and Scale Monitoring by Radioactive Tracers

As a result of reduction in original reservoir pressure, primary oil production decreases and water is usually injected to increase oil production. Injected water in special wells (injection wells) forces the oil remaining in certain layers to emerge from other wells (production wells) surrounding the injector. Efficiency of the water flooding process is highly dependent on the rock and fluid characteristics. In general, it will be less efficient if heterogeneity is present in the reservoir, such as permeability barriers or high permeability channels that impede a good oil displacement by the injected water [1]. On the other hand Most of the scales found in oil fields forms either by direct precipitation from the water that occurs naturally in reservoir rocks, or as a result of produced water becoming oversaturated with scale components when two incompatible waters meet ownhole. Radioactive tracers are now commonly used to monitor the progress of water injection in oil reservoir secondary recovery schemes. The present study attempts to establish the tracer technology as a reliable source of information in water injection, scaling experiments and reservoir evaluation such as reservoir heterogeneity. Also this paper discusses the factors involved in the selection of tracers, including their chemical form, and deals with the logistics of transporting and using radioactive materials offshore [15]. In a series of calcite scaling experiments in sand, Ca2+ was used as a tracer to monitor the CaCO3 precipitation. The results show that the introduction of tracer technology, for the first time in scaling experiments in porous media, has been successful [3].

Keywords:

Radiotracer , Waterflooding , Scale , heterogeneity