| Title | The Effect of Mineral Replacement Reactions on Sandstone Composition and Porosity Development in Hydrothermal Environments |
|---|---|
| Authors | David BRAUTIGAN, Allan PRING |
| Year | 2013 |
| Conference | Australian Geothermal Energy Conference |
| Keywords | mineral replacement reactions, porosity |
| Abstract | Hydrothermal mineral replacement reactions play an important role in controlling fluid transport in fluid flow environments such as geothermal energy systems. Porosity is introduced into the product mineral and changes in volume associated with mineral replacement reactions induce stress into the system resulting in micro fractures that may also change mineral permeability. Such changes have been studied principally via numerical modelling due to the widely held belief that the timescale of such reactions are incompatible with laboratory experiments. Very little experimental research has been conducted on the relative contributions to permeability of environmental variables such as temperature and pressure. We have developed in-situ flow-through reactors to simulate and study mineral replacement reactions occurring in hot sedimentary aquifer environments typical of those of interest to the geothermal industry. Our research aims were to study and quantify the effects fluid flow rate, temperature, pressure, and fluid composition on mineral replacement reaction rates. To this end, mineral samples consisting of quartz cemented with gypsum were exposed to varying pressure and temperature regimes. Changes in cement composition and associated porosity development were determined. The aim of this research was to identify the hydrothermal conditions and mineral compositions optimal for attaining the fluid flow rates necessary for geothermal energy development. It will provide an experimental basis for predictive modelling to identify potential future geothermal well locations. |