Title : Salt weathering effect on oil and gas sandstone formations
Abstract:
Sandstone rocks are important reservoirs of water, petroleum, gas and other fluids of Geoenergy. In the Western Region of Portugal, there are surface and near surface sandstone reservoirs close to salt formations. Sandstone samples collected from these surface reservoir formations were used in the present experimental study. An automatic salt crystallization accelerated ageing chamber prototype was developed and physical and mechanical tests were carried out on samples before and after sodium chloride crystallization ageing in order to evaluate the behavior of sandstone during accelerated weathering. The results of physical tests, i.e., effective porosity values showed an increase of more than 5%, whereas water absorption tests at low pressure (flow rate) revealed a reduction lower than 25%. The mechanical tests, i.e., compression and microdrilling resistance results highlighted a clear trend of decreasing values of mechanical parameters during salt crystallization weathering progress. Modes of failure were assessed, having monotonic and cyclic compression tests showed a decreasing difference of results between them, with salt crystallization weathering progress. The onset of degradation pattern of alveolization also was reached on specimens of the lower-porosity variety, through cycles of crystallization and dissolution of salts.
