Evidence of Multi-Process Matrix Diffusion in a Single Fracturefrom a Field Tracer Test

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Compared to values inferred from laboratory tests on matrix cores, many field tracer tests in fractured rock have shown enhanced matrix diffusion coefficient values (obtained using a single-process matrix-diffusion model with a homogeneous matrix diffusion coefficient). To investigate this phenomenon, a conceptual model of multi-process matrix diffusion in a single-fracture system was developed. In this model, three matrix diffusion processes of different diffusion rates were assumed to coexist: (1) diffusion into stagnant water and infilling materials within fractures, (2) diffusion into a degraded matrix zone, and (3) further diffusion into an intact matrix zone. The validity of the conceptual model ... continued below

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Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur & Molz, Fred J. June 11, 2005.

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Compared to values inferred from laboratory tests on matrix cores, many field tracer tests in fractured rock have shown enhanced matrix diffusion coefficient values (obtained using a single-process matrix-diffusion model with a homogeneous matrix diffusion coefficient). To investigate this phenomenon, a conceptual model of multi-process matrix diffusion in a single-fracture system was developed. In this model, three matrix diffusion processes of different diffusion rates were assumed to coexist: (1) diffusion into stagnant water and infilling materials within fractures, (2) diffusion into a degraded matrix zone, and (3) further diffusion into an intact matrix zone. The validity of the conceptual model was then demonstrated by analyzing a unique tracer test conducted using a long-time constant-concentration injection. The tracer-test analysis was conducted using a numerical model capable of tracking the multiple matrix-diffusion processes. The analysis showed that in the degraded zone, a diffusion process with an enhanced diffusion rate controlled the steep rising limb and decay-like falling limb in the observed breakthrough curve, whereas in the intact matrix zone, a process involving a lower diffusion rate affected the long-term middle platform of slowly increasing tracer concentration. The different matrix-diffusion-coefficient values revealed from the field tracer test are consistent with the variability of matrix diffusion coefficient measured for rock cores with different degrees of fracture coating at the same site. By comparing to the matrix diffusion coefficient calibrated using single-process matrix diffusion, we demonstrated that this multi-process matrix diffusion may contribute to the enhanced matrix-diffusion-coefficient values for single-fracture systems at the field scale.

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  • Journal Name: Transport in Porous Media; Journal Volume: 63; Journal Issue: 3; Related Information: Journal Publication Date: 06/2006

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  • Report No.: LBNL--58198
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 888770
  • Archival Resource Key: ark:/67531/metadc876029

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • June 11, 2005

Added to The UNT Digital Library

  • Sept. 21, 2016, 2:29 a.m.

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  • Sept. 29, 2016, 2:36 p.m.

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Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur & Molz, Fred J. Evidence of Multi-Process Matrix Diffusion in a Single Fracturefrom a Field Tracer Test, article, June 11, 2005; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc876029/: accessed December 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.