This PhD project is an integrated part of the advanced water flooding programme with the focus on improving oil recovery in tight chalk reservoirs in the Danish part of the North Sea.
In order to optimize the displacement of oil and to minimize the residual oil left behind by water flooding, different technologies are employed in water-based enhanced oil recovery (EOR).
The PhD project aims at investigate the potential of SmartWater flooding and its mechanism in carbonate reservoirs.
SmartWater processes involve changes in the ionic composition of the injection brine during water flooding of oil reservoirs. Theories have been put up to explain the mechanism of SmartWater flooding, however no consensus has been made.
The wettability alternation theory believes that the wettability of rock can be tuned to be more water wet by fluid-rock interaction, the attached oil can then be released from rock surface. The fines formation theory believes that CaCO3 and CaSO4 fines of micron scale can be formed in pore space by injection of SmartWater, these fines could act on water-oil interface and facilitate emulsification between water and oil. The migration of fines may divert the flow of water into inswept zone, so the swept efficiency can be improved.
Experimental approaches are to be carried out to understand and test the mechanism of SmartWater flooding. Preliminary selection of candidate fluids will be carried out by studying the interaction of fluid with rock powder.
Core flooding experiments will be carried out to further test the selected fluids. The underlying mechanism can be studied by using different injection schemes and core plugs with varying heterogeneity. Imbibition experiments with core plugs will also take place in order to test the effectiveness of Smart Water flooding in fractured low permeable chalk reservoir.
As the imbibition process is spontaneous and largely dependent on the wettability of the rock, it could give an indication of wettability change of the rock.