General Solution for Tidal Behavior in Confined and Semiconfined Aquifers Considering Skin and Wellbore Storage Effects. Issue 6 (22nd June 2020)

• Record Type: Journal Article
• Authors: Gao, Xuhua; Sato, Kozo; Horne, Roland N.
• Is Part Of: Water resources research. Volume 56:Issue 6(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-06-22
• Subjects: tidal response model -- skin effect -- wellbore storage -- Earth tide -- confined aquifer -- semiconfined aquifer; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2020WR027195
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Tidal analysis provides a cost‐effective way of estimating aquifer properties. Tidal response models that link aquifer properties with tidal signal characteristics, such as phase and amplitude, have been established in previous studies, but none of the previous models incorporate the skin effect. It is found in this study that the skin effect and the wellbore storage effect can have significant influence on the results of tidal analysis and should be included in tidal response models. New models are proposed with skin and wellbore storage effects fully incorporated so that aquifer information can be assessed more accurately based on tidal analysis. The models can be applied to confined aquifers with only horizontal flow or semiconfined aquifers with both horizontal flow and vertical flow. For confined aquifers, the new model indicates that positive skin leads to larger phase lag between the tidal response the the theoretical tide, and negative skin can reduce the phase lag or even cause a phase advance. For semiconfined aquifers, both the skin effect and the vertical flow affect the phase difference between the tidal response and the theoretical tide, and with the proposed model, contribution from these two sources can be separated and analyzed independently, making it feasible to evaluate semiconfined aquifer properties considering both factors. Increasing wellbore storage causes larger phase lag or smaller phase advance for both types of aquifers. Real‐world examples for confined and semiconfined aquifers are analyzed, respectively, to demonstrate practical applications of the proposed models. Key Points: Skin and wellbore storage effects have significant impacts on tidal analysis results and are thus included in tidal models The new models are established for both confined and semiconfined aquifers and demonstrated with real‐world examples The existence of a negative skin can cause a phase advance between the tidal response and the theoretical tide