Fluid inclusions as micro-samplers in batch experiments: A study of the system C-O-H-S-cement for the potential geological storage of industrial acid gas

Disposal in deep geological reservoirs is one potential solution for the storage of anthropogenic greenhouse gases and acid gases produced by the petroleum industry. Well cement durability during acid gas injection can be simulated in the laboratory and includes the study of toxic fluids (H2S + CO2) at high pressures (> 100 bar) and temperatures (> 100 °C). In order to reduce human risk, the experiments were carried out in microreactors (< 3 cm3). As fluid sampling during experiment is impossible, we propose a method of fluid capture by fluid inclusion synthesis in quartz: natural pre-existing fluid inclusions were emptied by heat-induced decrepitation and used as fluid microsamplers in batch microreactors. Experimental fluids were trapped at 200 °C and 500 bar by sealing the opened inclusions in microcracks. At the end of the experimental runs, quartz sections were collected and the fluid compositions determined by Raman spectroscopy at room and experimental P-T conditions. The number of fluid phases under experimental run conditions was checked indirectly by microthermometry. Variations of PVTX properties of the analysed inclusions are due to the combined effects of heterogeneous trapping and kinetics of well cement reactivity.