Laboratory investigations of compatibility of the Kuwait Group aquifer, Kuwait, with possible injection waters

A laboratory investigation of the compatibility of the Kuwait Group aquifer of Kuwait with desalinated seawater and reverse osmosis processed treated wastewater was carried out in anticipation of the artificial recharge of the aquifer in future. Even with the use of wax coating and freezing with liquid nitrogen, no core plugs could be extracted from the unconsolidated sections, and only the consolidated to semi-consolidated sections could be studied. The aquifer consists of silty and gravelly sand, and is often highly calcareous. The clay minerals present in the aquifer mostly belong to the montmorillonite and illite groups, with some palygorskite. Mercury injection porosimetry experiments on core plugs from the more cemented parts of the aquifer suggest that, to avoid significant clogging from suspended solids, particles down to a diameter of 8 μm should be filtered out of the injection water. Core flow experiments suggest that, for the samples examined, loss of permeability due to clay swelling is not very important. The blocking of pore throats by moving fines may be a more serious problem during injection. The geochemical simulation indicates that the possibility of scale formation when the injection waters come in contact with the Kuwait Group formation water is remote. Rather, there is a possibility of dissolution of carbonate minerals in the aquifer in contact with the injection waters.