On the possible contribution of clayey inter-layers to delayed land subsidence above producing aquifers
In recent years, measurements of land subsidence above pumped aquifers by permanent GPS and InSAR have exhibited some delay relative to drawdown ranging from months to years. The current modeling approaches accounting for water fluid dynamics and porous medium geomechanics may fail to predict suc...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-11-01
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| Series: | Proceedings of the International Association of Hydrological Sciences |
| Online Access: | https://www.proc-iahs.net/372/519/2015/piahs-372-519-2015.pdf |
| Summary: | In recent years, measurements of land subsidence above pumped aquifers by
permanent GPS and InSAR have exhibited some delay relative to drawdown
ranging from months to years. The current modeling approaches accounting for
water fluid dynamics and porous medium geomechanics may fail to predict such
a delay and may underestimate the land settlement after the well shutdown.
In the present communication, an investigation is made on the residual
compaction of the intervening clayey formations as a possible contribution
to retarded land subsidence. The pore pressure variation within the aquifer
and its propagation in the clay are simulated by a finite element flow
model, with the resulting pore pressure decline used as input data in a
hypo-plastic geomechanical model. A proper sensitivity analysis on (i) aquifer depth,
(ii) ratio between the sandy and the clayey layers thickness
and hydraulic conductivity, (iii) oedometric compressibility in first and
second loading cycles, is performed for a typical geology of a Quaternary
sedimentary basin. The results show that a certain fraction, up to 20 % of
the overall land subsidence, can take place after the shutdown of the
producing wells depending on actual basin, litho-stratigraphy and parameter
values. |
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| ISSN: | 2199-8981 2199-899X |