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Multiple-Point Statistics for Modeling Facies Heterogeneities in a Porous Medium: The Komadugu-Yobe Alluvium,Lake Chad Basin |
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| Authors: | |
| Institution: | (1) Institute of Life Science and Natural Resources, Korea University, Anam-dong, Sungbuk-ku, Seoul, 136-701, Korea;(2) Department of Statistics, Hankuk University of Foreign Studies, Yongin, 449-791, Korea;(3) Entomology Program, Department of Agricultural Biotechnology, Seoul National University, Seoul, 151-921, Korea;(4) Nanotoxtech Inc, #906, Gyeonggi Technopark, Ansan, 426-901, Korea;(5) Division of Environmental Science and Ecological Engineering, Korea University, 1-5ka Anam-dong, Sungbuk-ku, Seoul, 136-701, Korea; |
| Abstract: | Multiple-point statistics are used to model facies heterogeneities in the vadose zone of the Komadugu-Yobe River valley (southeastern Niger) which is presently submitted to an undergoing intensive agricultural development; therefore, increasing quantitative and qualitative pressures are exerted on groundwater resources. The sand–clay heterogeneities are analyzed by means of a Landsat image acquired during a high flow period over a 160 km stretch in the downstream part of the valley and a set of 50 boreholes drilled near the town of Diffa (4 km×4 km area). The horizontal variograms of heterogeneities are characterized by a noticeably constant length scale of 380 m and clayey objects are shown to be randomly distributed in space according to a Poisson process. A set of two-dimensional vertical images is built based on a Boolean procedure and the Snesim algorithm is used to simulate synthetic three-dimensional media. When the vertical correlation length is fitted, the three-dimensional model satisfactorily reproduces the second order statistics of heterogeneities and the specific facies patterns. |
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