Validation study of water weakening research from outcrop chalks performed on Eldfisk reservoir cores

Abstract Seawater injection for Enhanced Oil Recovery (EOR) purposes can increase the hydrocarbon recovery factor in carbonate reservoirs but are also responsible weakening their mechanical strength. This study investigates geomechanical behavior of oil-bearing reservoir chalk subject to reactive flow at conditions. The obtained results compared with previous from experiments on water-saturated outcrop chalks. Two unwashed cores Eldfisk Field North Sea mechanically tested a triaxial cell. saturated NaCl brine prior testing, addition residual oil. cores’ axial and radial deformations were monitored during hydrostatic stress loading creep under constant 50 MPa stress, 130 °C. During test, flooded 0.657 M NaCl, 0.219 M MgCl2, MgCl2 + 0.130 M CaCl2 synthetic seawater (SSW). average strain increased 0.03% 0.04% per day radially 0.06% axially after changing SSW brine. Flooding compaction rate 0.05% 0.09% 0.07% axially. Adding reduced 0.02% both axially, comparable reports experiments. composition-dependent core flooding was explained by dissolution primary calcite, confirmed Ion Chromatography, precipitation secondary Mg-bearing minerals, seen Scanning Electron Microscopy (SEM) analytics. Generally, aforementioned describing behaviors thermochemical influence this those studies chalk, thus supporting many years laboratory research as applicable context.