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| A dual-tracer method for assessment of reservoir heterogeneity |
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YAO Chuanjin1,2,3,4, LEI Guanglun1, XUE Shifeng2, ZHAO Yushi4,5, STEENHUIS T S3, CATHLES L M 4,5
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(1.School of Petroleum Engineering in China University of Petroleum, Qingdao 266580, China;2.College of Pipeline and Civil Engineering in China University of Petroleum, Qingdao 266580, China;3.Department of Biological and Environmental Engineering, Cornell University, Ithaca NY 14853, USA;4.KAUST-Cornell Center for Energy and Sustainability, Cornell University, Ithaca NY 14853, USA;5.Department of Earth and Atmospheric Science, Cornell University, Ithaca NY 14853, USA)
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| Abstract: |
| A dual-tracer method for the assessment of reservoir heterogeneity was proposed in this study based on the theory of fluid flow and tracer transport in heterogeneous porous media. Experiments were conducted using a single tube packed with sands simulating heterogeneous layers in order to validate the method. An ionic chemical tracer (KBr) and a fluorescent nano-particle tracer (Cdot) with different diffusion coefficient were used to indicate the total pore volume and flowing pore volume of the heterogeneous porous media, and thus to identify the reservoirs heterogeneity and to evaluate the water flooding effect. The results show that the breakthrough curves of KBr and Cdot under homogeneous conditions are almost coincident with each other, while obvious difference between the breakthrough curves can be observed under heterogeneous conditions. There is a significant difference for the fluid replacement or change rate (the fv value) in porous media between KBr and Cdot tracers, which can be used to identify the reservoirs heterogeneity by analyzing the output of KBr and Cdot and the variation of their fv values at a certain injection rate when considering the crossflow characteristics between the heterogeneous layers. These results can validate the feasibility and effectiveness of the dual-tracer method. |
| Key words: reservoir heterogeneity dual-tracer method convection-diffusion system breakthrough curve heterogeneous single-tube model volumetric sweep efficiency |
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