Neoformed Dolomite in Flooded Chalk for EOR Processes

Injection of MgCl2 into a Campanian chalk sample from Ličge (Belgium) for enhanced oil recovery over 516d revealed mineralogical changes. A new mineral phase (nano-sized magnesite) grew massively in the first centimeters of the tested core characterised by an increase of MgO about 90x the original composition and a depletion of CaO by more than 1/3. Furthermore, the test shows for the first time the neoformation of dolomite in the most affected slice of the flooded chalk. Here, dolomite grows in pore spaces of foraminifers as blocky sparite. Hence, there might be a possibility that neoformations of dolomite and magnesite are both related to the same process(es) but represent different stages during neoformation. MLA studies demonstrated that varieties of Mg-enriched carbonate minerals could be observed in the different flooded slices of the chalk. Alternatively, pore spaces are the likely locations of dolomite neoformation, while other Mg-rich phases may grow preferably on calcite-crystal surfaces. These results widens the field in applied mineralogical sciences as we show that when applying different analytical techniques it is possible to monitor mineralogical processes even in fine-grained chalk. We show that the combination of geological and engineering research gains fruitful results for the petroleum industry.