Core Flooding Experiments and Reactive Transport Modeling of Seasonal Heat Storage in the Hot Deep Gassum Sandstone Formation

Abstract

Seasonal storage of excess heat in hot deep aquifers is considered to optimize the usage of commonly available energy sources. The chemical effects of heating the Gassum Sandstone Formation to up to 150 °C is investigated by combining laboratory core flooding experiments with petrographic analysis and geochemical modeling. Synthetic formation water is injected into two sets of Gassum Formation samples at 25, 50 (reservoir temperature), 100, and 150 °C with a velocity of 0.05 and 0.1 PV/h, respectively. Results show a significant increase in the aqueous concentration of silicium and iron with increasing temperature due to dissolution of silica and siderite. Increasing the reservoir temperature from 50 to 100 °C enhanced the naturally occurring weathering of Na-rich feldspar to kaolinite. Dissolution of quartz increased sharply above 100 °C and was the dominating process at 150 °C, resulting in a significant increase in the aqueous silicium concentration. At temperatures ≤100 °C, the silicium concentration was controlled by a quasi-stationary state between feldspar dissolution and kaolinite precipitation whereas the concentration was kinetically controlled by quartz dissolution at 150 °C. Furthermore, a strong coupling between dissolution, precipitation, and flow velocity was observed. The results of this study show that the effects of heat storage of up to 150 °C in the Gassum Formation in the Stenlille area is expected to have only minor effects on the properties of the reservoir and that storage of excess heat in the Gassum Formation in the Stenlille area may be possible provided operational precautions are taken.

Impact of Microheterogeneity on Upscaling Reactive Transport in Geothermal Energy

“…We assumed that the rock was composed of quartz (SiO 2 ), kaolinite (Al 2 Si 2 O 5 (OH) 4 ), albite (NaAlSi 3 O 8 ), anorthite (CaAl 2 Si 2 O 8 ), and siderite (FeCO 3 ) minerals to represent a realistic sandstone mineral assemblage based on a typical geothermal site in Denmark, named the Gassum formation. 49 The network was composed of pore bodies (spheres) and pore throats (cylinders), which both had a volume and surface. Pore units (i.e., each pore unit comprises a pore body and half-length of the connecting pore throats) were either reactive or nonreactive.…”

“…As siderite is not widespread in sandstone rocks and is highly active, its amount was assumed to be low (1%). 49 Boundary condition for the network was the constant pressure at the inlet and outlet (which resulted in constant injection flow rate). The injection water at the inlet had fixed pH, chemical composition, and concentrations.…”

Effect of High Temperature and High Pressure of Water on Micro-Characteristic and Splitting Tensile Strength of Gritstone

“…For instance, solubility of silicates increases with the increasing temperature. While, solubility of carbonates is much lower than that of silicates with the increasing temperature (Holmslykke et al, 2017). Dissolution/precipitation processes of rocks in the TES may affect the permeability of TES by changing the pore space geometry and pore connectivity of rocks (Ngwenya et al, 2000).…”

“…Due to the limitation of test technique level, experiences with higher temperatures (about 150 • C) is rarely reported (Vetter et al, 2012). However, field heat storage tests in closed shallow sandstone aquifers below 150 • C show that calcium carbonate precipitation is the key hydrochemical problem (Holmslykke et al, 2017). Furthermore, researches on macro-mechanical strength of rocks in TES systems in shallow aquifers including traditional rock fracturing Zhou, 2015, 2017a,b;Bi et al, 2016a,b;Zhao et al, 2016Zhao et al, , 2017aZhao et al, ,b, 2018aZhao et al, , 2019Zhou et al, in press;Zhou and Bi, 2016), hydraulic fracturing (Breede et al, 2013;Zhao et al, 2018b), thermal fracturing (Zhou and Bi, 2018), shear stimulation (Zhu and Huang, 2019), and multilateral wells (Shi et al, 2018).…”

“…Furthermore, researches on macro-mechanical strength of rocks in TES systems in shallow aquifers including traditional rock fracturing Zhou, 2015, 2017a,b;Bi et al, 2016a,b;Zhao et al, 2016Zhao et al, , 2017aZhao et al, ,b, 2018aZhao et al, , 2019Zhou et al, in press;Zhou and Bi, 2016), hydraulic fracturing (Breede et al, 2013;Zhao et al, 2018b), thermal fracturing (Zhou and Bi, 2018), shear stimulation (Zhu and Huang, 2019), and multilateral wells (Shi et al, 2018). And then, the mechanical characters of hot dry rock under thermohydro-mechanical (THM) effect (Breede et al, 2013;Possemiers et al, 2014;AbuAisha et al, 2016;Holmslykke et al, 2017;Schmidt et al, 2017;Chen et al, 2018;Kumari et al, 2018;Pandey et al, 2018;El Sharawy and Nabawy, 2019) also can be borrowed in to TES systems. These studies are focused on the influence of thermal effect on the mechanical properties of sandstone.…”