Abstract

Water injection is extensively applied as an oil recovery method. This generates a large volume of produced water that must be separated from the production stream and disposed with technical, economic and environmental consequences. The optimized use of water resources in the oil production is linked with the sweep efficiency or drainage of that water in the reservoir, which is the aim of this article. The inaccessibility of petroleum reservoirs associated with the lack of tools able to effectively characterize the rock formation channels make tracers a very important qualitative and quantitative evaluation technique to date and indispensable to the management of such water. The hydrodynamic characterization of channels traversed is possible by previously marking the fluid with a water-soluble conservative tracer, which, by definition, flows through the formation dissolved in water without interacting with the rock-fluid system, i.e., without chemical reaction or adsorption (conservative or ideal tracer). This work builds a connection between laboratory experiments and field data. Laboratory tests were performed in a linear (1-D) physical model (with target-field rock) and in a 5-spot physical model (outcrop rock), using the target field water and with temperature of the target field (1-D test) or room temperature (2-D test). The field application was performed in a reduced pilot consisting of an inverted 5-spot unit (1 injection well and 4 production wells). The mathematical simulation of 1-D laboratory data was made using the traditional convection-diffusion equation. Field and laboratory 5-spot data were adjusted using a mathematical model (2-D convection-diffusion equation) and its analytical solution through the Generalized Integral Transform Technique (GITT) for an ideal 5-spot pattern. This study suggests that working with a tracer pulse, instead of a slug, is the best strategy and facilitates the interpretation of lab and/or field results. Furthermore, it is possible to estimate the sweep efficiency using the mathematical interpretation of a pulse. The collected information allows the interpretation of the hydrodynamic characteristics of the studied field area and serves as a basis for future EOR applications of polymers and/or surfactants.

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