资源环境科技发展态势分析平台

Quantitative interpretation of the tidal response of water levels measured in wells has long been made either with a model for perfectly confined aquifers or with a model for purely unconfined aquifers. However, many aquifers may be neither totally confined nor purely unconfined at the frequencies of tidal loading but behave somewhere between the two end-members. Here we present a more general model for the tidal response of groundwater in aquifers with both horizontal flow and vertical leakage. The model has three independent parameters: the transmissivity (T) and storativity (S) of the aquifer and the specific leakage (K'/b') of the leaking aquitard, where K' and b' are the hydraulic conductivity and the thickness of the aquitard, respectively. If T and S are known independently, this model may be used to estimate aquitard leakage from the phase shift and amplitude ratio of water level in wells obtained from tidal analysis. We apply the model to interpret the tidal response of water level in a US Geological Survey (USGS) deep monitoring well installed in the Arbuckle aquifer in Oklahoma, into which massive amount of wastewater coproduced from hydrocarbon exploration has been injected. The analysis shows that the Arbuckle aquifer is leaking significantly at this site. We suggest that the present method may be effective and economical for monitoring leakage in groundwater systems, which bears on the safety of water resources, the security of underground waste repositories, and the outflow of wastewater during deep injection and hydrocarbon extraction.

Plain Language Summary Quantitative interpretation of the tidal response of the hydraulic head of an aquifer has been made either with a model for perfectly confined aquifers or with that for purely unconfined aquifers. However, many aquifers may neither be totally confined nor purely unconfined at the frequencies of tidal loading but behave somewhere between the two end-members. A model for the interpretation of the tidal response of such aquifers, however, is currently lacking. Here we derive a new model for the tidal response of a leaky aquifer and apply the model to interpret the tidal response of water level in a USGS Oklahoma deep monitoring well installed in the Arbuckle aquifer, into which a massive amount of wastewater coproduced from hydrocarbon exploration has been injected. The analysis suggests that the Arbuckle aquifer is leaking significantly at this site. It also shows that Earth tide analysis of water level in wells may be useful for continuous monitoring of leakage of groundwater system, which bears on the safety of water resources, the security of underground waste repositories, and the outflow of wastewater during hydrocarbons extraction.