Subsurface tidal analysis requires only continuous pressure monitoring data and therefore can be a cost-effective technique for estimating aquifer properties. The tidal behavior of a well in a semiconfined aquifer can be described by a diffusion equation that includes a leakage term. This approach is valid for thin aquifers, as long as the overlying layer has low permeability relative to the main aquifer. However, in cases where the aquifer is not thin and the permeability of the overlying layer is not low, using the existing solutions based on these approximations may lead to unsatisfactory outcomes. Alternative solutions for both vertical and horizontal wells were obtained by solving the standard diffusion equation, with leakage expressed as a boundary condition. Furthermore, a nondimensional number was derived mathematically, which forms the basis for a quantitative criterion to assess the applicability of the existing solutions. In the case of a vertical well, the existing solution exhibits acceptable error only if the nondimensional number is less than 0.245. Our new solution extends this upper limitation to 0.475. However, when the number is greater than 0.475, both the existing solution and our new solution are invalid due to the invalid uniform flowrate assumption. For a horizontal well, when the number is less than 0.245, the existing solution is suitable with acceptable error. Our new solution effectively overcomes this limitation. Finally, the new solution was applied to the case of the Arbuckle aquifer to demonstrate the improved validity of the new solution compared to the existing one.

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.