Experimental observations of aquifer storage and recovery in brackish aquifers using multiple partially penetrating wells

Abstract

Aquifer storage and recovery systems using multiple partially penetrating wells (MPPW-ASR) can form a viable solution to the problem of freshwater buoyancy when using brackish aquifers for freshwater storage. This study presents the result of a series of laboratory experiments that aimed at visualizing the shape of freshwater bodies injected into a brackish aquifer and determining the effect on the recovery efficiency (RE) of several MPPW-ASR operational variables. A model aquifer was built in a Plexiglas tank using glass beads and water was injected and abstracted through point and vertical wells, which were operated in various combinations. Numerical models were used to support the interpretation of the time-lapse photographs, and showed that three-dimensional flow effects had to be considered for a correct interpretation of the visible dye patterns. Upward migration of both fresh (during injection) and brackish water (during recovery) along the vertical wells was observed, indicating that the role of well infrastructure as conduits is a critical design criterion for real-world systems. Gravitational instabilities formed when freshwater did not extend all the way to the top of the aquifer, and this negatively impacted the RE by causing greater mixing. The positive freshwater buoyancy led to freshwater bodies that became narrower with depth, and the formation of thin, elongated buffer zones along the aquifer top in multicycle experiments. Up-coning below abstraction wells resulted in lower RE values, reinforcing the potential of scavenger wells to enhance MPPW-ASR system performance.

Using multiple partially-penetrating wells (MPPWs) to improve the performance of high-temperature ATES systems: Well operation, storage conditions and aquifer heterogeneity

“…The existing knowledge in the field of aquifer storage and recovery (ASR) could also be applied in HT-ATES systems. In ASR systems the selection of an efficient injection and abstraction well operation scheme in a MPPW setup is successfully used to maintain a stable fresh water volume and to actively limit the mixing potential in brackish aquifers during fresh water storage (Zuurbier et al, 2014;Witt et al, 2021).…”

“…Instead of using the density difference compensation method to minimize the effects of buoyancy-driven flow, it can be counteracted hydraulically using Multiple Partially Penetrating Wells (MPPWs) in HT-ATES systems. Implementation of PPWs has already shown to be beneficial for aquifer storage and recovery of fresh water in brackish aquifers (Maliva and Missimer, 2010;Zuurbier et al, 2014;Witt et al, 2021).…”

Managed aquifer recharge with marginal water for irrigation and contaminant attenuation

“…Witt et al (2021) presented injection-extraction experiments of density driven flow with several fullypenetrating and partially-penetrating well configurations, where freshwater was injected into a laboratory-scale brackish aquifer. Experimentally, doubling the injection-extraction rate and halving the injection-extraction duration (maintaining the total volume) led to an increase in recovery efficiency.…”