Alteration of fluid properties during the initial operation of a geothermal plant: results from in situ measurements in Gro Schonebeck

作者：Feldbusch Elvira; Regenspurg Simona^*; Banks Jonathan; Milsch Harald; Saadat Ali

来源：Environmental Earth Sciences, 2013, 70(8): 3447-3458.

DOI：10.1007/s12665-013-2409-9

• Geothermal energy
• Geothermal fluid
• Geochemical monitoring
• Physicochemical properties of fluids
• North German Basin
• Rotliegend
• In situ laboratory Gro beta Schonebeck

Recently, the thermal fluid loop has been established and continuosly operated for 7 days at the geothermal in situ laboratory in Gro Schonebeck (North German Basin). During this initial phase of fluid production, the fluid temperature, measured at the surface, continuously increased until a stable value of about 98 A degrees C was established. Fluid physicochemical properties (pH, redox, density, temperature, and pressure) were measured online and in situ with a newly developed fluid monitoring system (FluMo). Additionally, fluid samples have been collected at various temperatures (in 5-10 A degrees C steps) directly at the production well at about 10 bar pressure. From the pressurized sampling tool, the fluid was directly transferred into a heated autoclave, which allowed filtration (0.2 mu m) in the absence of oxygen. Physicochemical parameters [pH, redox, electric conductivity, total dissolved solids (TDS)] as well as acid capacity (K (S 4.3)) of these samples have been measured onsite at atmospheric conditions. Concentrations of anions, total organic carbon, and metals were analyzed later in the laboratory. Both, measurements in collected samples or in situ (FluMo) analysis of most the parameters density, electric conductivity, or TDS indicated relatively constant values over the whole production time (1.17-1.18 g center dot A cm(-3), 215-221 mS center dot A cm(-1), 241-260 g center dot A L-1, respectively). Good correlation was also found for pH values (pH = 6.6-6.9), whereas the redox values varied between -1 and 46 mV when determined at 25 A degrees C and decreased strongly when measured in situ with increasing temperature (-110 mV at 90 A degrees C). The elemental composition of collected samples remained also relatively constant for most compounds and was clearly higher as compared with samples collected in 2011. Results of this study demonstrate that realistic, comprehensive, and time-resolved physicochemical data can be obtained by FluMo. These detailed data sets can be crucial to understand the complex geochemical processes in a thermal water loop and eventually to take required measures on time.

• 出版日期2013-12