Articles | Volume 21, issue 2
Hydrol. Earth Syst. Sci., 21, 721–733, 2017
Hydrol. Earth Syst. Sci., 21, 721–733, 2017

Research article 03 Feb 2017

Research article | 03 Feb 2017

Modeling 3-D permeability distribution in alluvial fans using facies architecture and geophysical acquisitions

Lin Zhu1, Huili Gong1, Zhenxue Dai2,3, Gaoxuan Guo4, and Pietro Teatini5 Lin Zhu et al.
  • 1College of Resource Environment and Tourism, Capital Normal University, Laboratory Cultivation Base of Environment Process and Digital Simulation, Beijing, China
  • 2College of Construction Engineering, Jilin University, Changchun, 130021, China
  • 3Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico, USA
  • 4Beijing Institute of Hydrogeology and Engineering Geology, Beijing, China
  • 5Department of Civil, Environmental and Architectural Engineering, University of Padova, Padova, Italy

Abstract. Alluvial fans are highly heterogeneous in hydraulic properties due to complex depositional processes, which make it difficult to characterize the spatial distribution of the hydraulic conductivity (K). An original methodology is developed to identify the spatial statistical parameters (mean, variance, correlation range) of the hydraulic conductivity in a three-dimensional (3-D) setting by using geological and geophysical data. More specifically, a large number of inexpensive vertical electric soundings are integrated with a facies model developed from borehole lithologic data to simulate the log10(K) continuous distributions in multiple-zone heterogeneous alluvial megafans. The Chaobai River alluvial fan in the Beijing Plain, China, is used as an example to test the proposed approach. Due to the non-stationary property of the K distribution in the alluvial fan, a multiple-zone parameterization approach is applied to analyze the conductivity statistical properties of different hydrofacies in the various zones. The composite variance in each zone is computed to describe the evolution of the conductivity along the flow direction. Consistently with the scales of the sedimentary transport energy, the results show that conductivity variances of fine sand, medium-coarse sand, and gravel decrease from the upper (zone 1) to the lower (zone 3) portion along the flow direction. In zone 1, sediments were moved by higher-energy flooding, which induces poor sorting and larger conductivity variances. The composite variance confirms this feature with statistically different facies from zone 1 to zone 3. The results of this study provide insights to improve our understanding on conductivity heterogeneity and a method for characterizing the spatial distribution of K in alluvial fans.

Short summary
We developed a method to characterize the distribution and variance of the hydraulic conductivity k in a multiple-zone alluvial fan by fusing multiple-source data. Consistently with the scales of the sedimentary transport energy, the k variance of the various facies decreases from the upper to the lower portion along the flow direction. The 3-D distribution of k is consistent with that of the facies. The potentialities of the proposed approach are tested on the Chaobai River megafan, China.