Chemical changes in fluid composition due to CO2 injection in the Altmark gas field: preliminary results from batch experiments

摘要: Dissolution–precipitation phenomena induced by CO2 injection to Altmark Permian sandstone were observed through laboratory experiments carried out under simulated reservoir conditions (125 °C and 50 bars of pressure). The rock sample was collected from the gas reservoir, which is being considered for enhanced recovery. Two sets performed with pulverized samples in a closed batch reactor either pure water (run 1) or 3 M aqueous NaCl solution 2) reacted injected 3, 5, 9 days. liquid analyzed inductively coupled plasma optical emission spectroscopy total reflection X-ray fluorescence, where latter proved be feasible alternative conventional analytical techniques, especially since only small volumes (about 10 μl) are needed. Chemical analysis both fluids (water brine) indicated significant dissolution calcite anhydrite solution, might crucial process during injection. brine compared at beginning reaction. Moreover, progressive higher Si4+/Al3+ molar ratios (in average factor 3) quartz dissolution. Thermodynamic calculations mineral saturation indices highlighted Ca-bearing minerals, agreement experimental results. Modeling enabled an evaluation processes minerals low-salinity region, yet hindrances model more saline emphasize need further studies order parameterize models deep aquifer conditions.