Hydrochemical and operational parameters driving carbonate scale kinetics at geothermal facilities in the Bavarian Molasse Basin

Geothermal Energy

Science – Society – Technology

Table 2 Analysis of geothermal waters at the wellhead of the investigated facilities

Group	Site	TDS	\(\hbox {CO}_2\)	\(\hbox {HCO}_{3}^{-}\)	\(\hbox {Ca}^{2+}\)	\(\hbox {Mg}^{2+}\)	Ca/Mg	Scales
	Nr.	(mg/L)	(mmol/L)	(mmol/L)	(mmol/L)	(mmol/L)	(mmol/mmol)
1	13	634	2.11	5.20	0.93	0.39	2.4
1	15	680	2.00	5.90	0.96	0.45	2.1	Fe-sulf.
2	17	661	2.00	4.11	0.85	0.18	4.6	cc, Fe-sulf., Cu-sulf., apatite
2	8	656	4.79	4.23	0.42	0.09	4.5	cc, vat, Fe-sulf.
2	10	548	1.80	4.52	0.25	0.08	3.0	cc, Fe-sulf., Cu-sulf.
2	7	648	2.70	3.36	0.58	0.12	5.0	cc, Fe-sulf.
2	9	605	4.79	4.33	0.51	0.11	4.6	cc, Fe-sulf., Cu-sulf.
2	16	689	2.60	4.92	0.71	0.18	3.9
3	5	917	4.41	5.08	1.09	0.25	4.4	cc
3	6	902	4.80	4.98	0.85	0.23	3.7	cc, Fe-sulf., Cu-sulf.
4	2	4844	3.91	7.24	3.57	1.29	2.8
4	3a	1109	3.00	12.85	1.05	0.24	4.3	cc, Fe-sulf.
4	3b	2083	5.02	5.00	2.36	0.75	3.1	cc, Fe-sulf.

Group	Site	(\(\hbox {Na}^{+}+ \hbox {K}^{+}- \hbox {Cl}^{-})/\)	\((\hbox {S}^{2-} + \hbox {HS}^{-})/\)	pH*	SI	Water type	Scales
	Nr.	\(\hbox {HCO}_{3}^{-}\) (meq/meq)	\(\hbox {SO}_4^{2-}\) (meq/L)		calcite*		Scales
1	13	0.56	0.54	**	**	\(\hbox {Na}-\hbox {Ca}-\hbox {HCO}_{3}-\hbox {Cl}\)
1	15	0.57	0.74	**	**	\(\hbox {Na}-\hbox {Ca}-\hbox {HCO}_{3}-\hbox {Cl}\)	Fe-sulf.
2	17	0.61	0.58	6.75	0.30	\(\hbox {Na}-\hbox {Ca}-\hbox {HCO}_{3}-\hbox {Cl}\)	cc, Fe-sulf., Cu-sulf., apatite
2	8	0.84	1.00	6.72	0.24	\(\hbox {Na}-\hbox {HCO}_{3}-\hbox {Cl}\)	cc, vat, Fe-sulf.
2	10	0.92	0.66	**	**	\(\hbox {Na}-\hbox {HCO}_{3}-\hbox {Cl}\)	cc, Fe-sulf., Cu-sulf.
2	7	0.70	0.99	6.66	0.22	\(\hbox {Na}-\hbox {HCO}_{3}-\hbox {Cl}\)	cc, Fe-sulf.
2	9	0.69	0.76	6.69	0.20	\(\hbox {Na}-\hbox {HCO}_{3}-\hbox {Cl}\)	cc, Fe-sulf., Cu-sulf.
2	16	0.67	0.61	6.73	0.17	\(\hbox {Na}-\hbox {HCO}_{3}-\hbox {Cl}\)
3	5	0.59	2.06	6.42	0.23	\(\hbox {Na}-\hbox {Ca}-\hbox {HCO}_{3}-\hbox {Cl}\)	cc, cc
3	6	0.44	1.89	**	**	\(\hbox {Na}-\hbox {Cl}-\hbox {HCO}_{3}\)	cc, Fe-sulf., Cu-sulf.
4	2	0.82	8.11	**	**	Na-Cl
4	3a	0.67	1.86	**	**	\(\hbox {Na}-\hbox {Cl}-\hbox {HCO}_{3}\)	cc, Fe-sulf.,cc
4	3b	0.29	4.00	**	**	\(\hbox {Na}-\hbox {Cl}-\hbox {HCO}_{3}\)	cc, Fe-sulf.,cc

Total dissolved solids = TDS. * = calculated values. **No data for back-calculation. Four groups of geothermal waters can be distinguished: 1) low-saline dolomite in the northeast of Munich, 2) low-saline limestone southeast of Munich, 3) medium-saline limestone southeast of Munich, 4) high-saline gas-rich western Molasse Basin. Water type = according to Furtak & Langguth (1965)