Chelating agents for diluted geothermal brine reinjection

Abstract

Abstract“Blue energy” could be produced by exploiting the large salinity gradient between geothermal fluids and freshwater through a SaltPower system. This study is an attempt to select the most favorable chemicals to avoid injectivity issues when a diluted geothermal fluid resulting from the SaltPower system is returned to the reservoir. Three synthetic chelating agents (oxalic acid, EDTA, and EDDS) and one natural (humic acid) were evaluated through speciation simulations and isothermal titration calorimetry (ITC) experiments. The speciation simulation results indicate that the degree of complexing is highly dependent on pH and chelating agent type. The ITC experiments show that the total heat for the formation of soluble metal–ligand complexes in the rock + geothermal brine system follows: EDTA > EDDS > oxalic acid > humic acid. The simulations and calorimetry results suggest that EDTA could be used to avoid the precipitation of Fe(III) oxides and other minerals (e.g., calcite and dolomite) inside the porous media upon the reinjection of diluted geothermal brine coming from SaltPower electricity production.

Microcalorimetric Study of Carbonating Produced Water as a Promising CO2 Storage and Enhanced Oil Recovery Method

“…Awareness of climate change and its negative effects has increased since the global concentration of carbon dioxide (CO 2 ) in the atmosphere has been rising significantly [1]. CO 2 emission is an inevitable side-effect of burning fossil fuels, which play an important role in the global energy mix of the 20th century [2]. In order to achieve substantial reductions in greenhouse gas emissions while enabling sustainable energy production, anthropogenic CO 2 must be captured, transported, and stored subsequently in geological formations such as deep saline aquifers, coal beds, and depleted oil and gas reservoirs [3][4][5].…”

“…The degree of accuracy of this technique is higher than those of alternatives (e.g., Van 't Hoff equation) because the enthalpy is determined from measurements [16]. In our previous works, microcalorimetry was proven to be useful for the understanding of complex rock-fluid and fluid-fluid interactions for both enhanced oil recovery and geothermal energy production [2,13,[16][17][18].…”