Analysis of Tidal Behavior of a Horizontal Well to Determine Reservoir Properties

Abstract

Tidal analysis requires only continuous pressure monitoring data and therefore is a cost-effective technique for estimating reservoir properties. Previous tidal analysis work focused on vertical wells. This study developed and solved tidal response models for a horizontal well considering skin effect and wellbore storage in three classical reservoir types: confined reservoir, semiconfined reservoir, and reservoir with mixed boundaries. Green's function, source functions, Laplace transform, and Duhamel's principle were used to solve the models and obtain analytical solutions in Laplace space. Then, Laplace transform numerical inversion was utilized to invert the Laplace space solutions to time-domain solutions. Variable condition analysis was conducted to analyze the effects of different parameters (wellbore storage, skin effect, well length, well direction - horizontal or vertical, and vertical leakage) on tidal behavior: For confined reservoirs, the influence of skin effect and wellbore storage (under the condition of positive skin effect) both tend to decrease the tidal amplitude ratio and increase the tidal phase lag. Longer wells lead to a smaller tidal amplitude ratio and lead to a larger tidal phase lag for small wellbore storage, and smaller tidal phase lag for large wellbore storage. For reservoirs with mixed boundaries, the effect of wellbore storage depends on the value and sign of skin factor. A horizontal well with larger skin effect will have larger tidal phase lag and tidal amplitude attenuation. For a semiconfined reservoir, the tidal amplitude ratio first increases with increasing vertical leakage but then decreases when there is a large vertical leakage. Vertical leakage tends to decrease the tidal phase lag or increase the tidal phase advance.

Impact of Depth‐Dependent Heterogeneity in Aquifers on the Response of Unsaturated‐Saturated Flow to Earth Tides

“…Understanding the amplitude and phase of these groundwater fluctuations is of utmost importance, as they are intricately linked to aquifer parameters, with hydraulic conductivity playing a key role. As such, numerous studies have focused on estimating aquifer parameters by examining the correlation between groundwater fluctuations and Earth tides (Bredehoeft, 1967; Cutillo & Bredehoeft, 2011; Lai et al., 2013; Lu et al., 2022; Sun & Xiang, 2019; Vanderkamp & Gale, 1983; Xue et al., 2016). Over the years, various analytical models have been developed to investigate Earth tidal phenomena in aquifers (Detournay & Cheng, 1993; Hsieh et al., 1987; Roeloffs, 1996; H. Wang, 2000; C.‐Y.…”

Capillary Impact on Tidal Response of Groundwater in Unconfined Aquifers With Finite Thickness, Anisotropy and Wellbore Storage—An Analytical Model

“…This periodic deformation causes aquifers to dilate and contract, forcing the pore pressure to fluctuate and groundwater to flow between aquifers and wells, resulting in periodic fluctuations of water level in wells. Phase shift and amplitude ratio between the observed tidal fluctuations of water level and the reference tidal strains have been used to evaluate the hydraulic properties of aquifers (Cutillo & Bredehoeft, 2011; Lu et al., 2022; McMillan et al., 2019; Vanderkamp & Gale, 1983; Wahr, 2011; Xu et al., 2021). Although there is a rapid increase in the use of the tidal response of groundwater as a tool to study the permeability of the upper crust (Bredehoeft, 1967; Hsieh et al., 1987; Roeloffs, 1996; Sun & Xiang, 2019; Wang, 2000; Wang et al., 2018; Xue et al., 2013, 2016), a thorough understanding on the response of groundwater to tides is still lacking, particularly on the impact of the unsaturated zone on the tidal response.…”