Improved Characterization of Groundwater Flow in Heterogeneous Aquifers Using Granular Polyacrylamide (PAM) Gel as Temporary Grout

Abstract

The range of options for investigation of hydraulic behavior of aquifers from boreholes has been limited to rigid, cumbersome packers, and inflatable sleeves. Here we show how a new temporary borehole sealing technique using soft grains of polyacrylamide (PAM) gel as a sealing material can be used to investigate natural groundwater flow dynamics and discuss other possible applications of the technology. If no compressive stress is applied, the gel packing, with a permeability similar to open gravel, suppresses free convection, allowing for local temperature measurements and chemical sampling through free‐flowing gel packing. Active heating laboratory and field experiments combined with temperature measurements along fiber optic cables were conducted in water‐filled boreholes and boreholes filled with soft grains of polyacrylamide gel. The gel packing is shown to minimize the effect of free convection within the well column and enable detection of thin zones of relatively high or low velocity in a highly transmissive alluvial aquifer, thus providing a significant improvement compared to temperature measurements in open boreholes. Laboratory experiments demonstrate that under modest compressive stress to the gel media the permeability transitions from highly permeable to nearly impermeable grouting. Under this configuration the gel packing could potentially allow for monitoring local response pressure from the formation with all other locations in the borehole hydraulically isolated.

Measuring Fracture Flow Changes in a Bedrock Aquifer Due to Open Hole and Pumped Conditions Using Active Distributed Temperature Sensing

“…Poorly consolidated rock or unstable boreholes could make the installation and removal of liners difficult. This would require other ways to seal the borehole such as permanently grouting the cable in place or perhaps the polyacrylamide gel beads described by Klepikova et al (2018). Also, while the early issues of small amounts of flow along the cable behind the liner described by Maldaner et al (2019) have been resolved by increasing the hydrostatic pressure in the liner, this may be difficult at sites with shallow water tables.…”

“…While this can help, the majority of the borehole remains unsealed, and therefore, vertical flow within the borehole is still possible and has in some cases led to inflated flow measurements in point dilution experiments (Maldaner et al, 2018). Less conventional methods have been tested recently to prevent free convection and flow within borehole such as the use of granular polyacrylamide gel beads (Klepikova et al, 2018). Finally, flexible, impermeable fabric borehole liners have been demonstrated as an effective means to temporarily seal boreholes.…”

Temperature log simulations in high-enthalpy boreholes

“…However, several studies have reported the existence of another key factor in the heat transfer, which is free convection caused by density differences arising from vertical temperature gradients (Diment 1967;Gretener 1967;Pfister and Rybach 1995;Berthold and Börner 2008;Eppelbaum and Kutasov 2011;Klepikova et al 2018). The critical parameters for the free convection process can be indicated by the following equation (Diment and Urban 1983):…”

Parametric Study of Polymer-Nanoparticles-Assisted Injectivity Performance for Axisymmetric Two-Phase Flow in EOR Processes

“…Thereby, they can fill tight, small cracks and pores and induce fundamental changes in permeability reduction due to their strong impact on pore plugs. Furthermore, there are a wide variety of factors that exert a considerable influence on controlling nanoparticles migration, such as increasing flow velocity and rise of pressure drop during the low-salinity water-flooding procedures [19]. In this paper, a mathematical model of polymer-nanoparticles-assisted injectivity performance was developed to control the mobility of nanoparticles migration.…”

“…PAM (polyacrylamide): Due to its high value of molecular weight (approximately more than 10 6 gr./mole) that usually performed as a thickening agent for the aqueous solutions. Moreover, PAM has its stable properties at the temperature of 90 °C at the normal salinity and at the salinity of seawater; the temperature is set up at 62 °C Hence, it is worthwhile that this type of polymer would be restricted on the on-shore performances [ 19 ].…”