Enhanced Oil Recovery Methods targeting Danish North Sea Chalk Reservoirs

Smart Water flooding is a promising enhanced oil recovery method where the modification of salinity and/or ionic composition leads to recovery of additional oil.

Several different types of experiments have been conducted and various mechanisms have been proposed to explain the behaviour of rock-oil-brine interaction in the porous medium.

However due to the diversity of observation from different experiments and complexity and heterogeneity of studied systems in carbonate rocks, a consensus regarding the main mechanism for the increase in oil recovery has still not been achieved.

The aim of this PhD project is to provide more details and understanding regarding the application of Smart Water for Danish North Sea reservoirs.

More than half of the discovered petroleum resources are classified as carbonate reservoirs which can be subdivided into chalk, limestone, and dolomite. Due to the low tendency of carbonate reservoirs in being wet with water, low permeability, and heterogeneity of rock properties, the ultimate oil recovery factor usually is not more than 30%.

Most preview studies have verified that water injection with lower salinity has beneficial impacts on the ultimate oil recovery. Higher injectivity due to lower suspended solids content, decreased corrosion of wells, easier implementation and lower capital and operation costs of this technique compared to other EOR methods can be considered as prospective advantages of Smart Water injection.   

Wettability alteration is one of the mechanisms that is claimed to be the reason for the increase in oil recovery due to the application of Smart Water. Smart Water can be made by optimising the ionic composition of the injected fluid in such a way that the change in the equilibrium of the initial crude oil, brine, and rock system will modify the initial wetting conditions. Not only is the concentration of the active ions such as Ca2+, Mg2+, and SO42- important for wettability alteration, but also the amount of monovalent ions, such as Na+ and Cl-, salinity of formation brine, oil properties, surface charges of oil and rock, and reservoir temperature can play an essential role in increasing oil production.

Significant research is required to unlock the mechanisms of Smart Water injection into carbonate rocks. The controlling mechanism can be multiple and the interaction between rock-fluid and fluid-fluid should be studied extensively. To understand the impact of mentioned parameters, extensive core flooding experiments at reservoir condition, imbibition tests, contact angle measurement test, and other relevant experiments will be carried out. This will hopefully make it possible to reveal the most important governing mechanisms of the additional oil recovery by application of the Smart Water.

The work is carried out at the Danish Hydrocarbon Research and Technology Centre (DHRTC) at DTU from 2017 to 2020 under the supervision of Senior Researcher Sidsel Marie Nielsen (DHRTC) and Associate Professor Alexander Shapiro (Department of Chemical and Biochemical Engineering). The PhD project is funded by DHRTC.

Contact

Mirhossein Taheriotaghsara
PhD student
Centre for Oil and Gas - DTU
+45 71 66 37 75

Contact

Sidsel Marie Nielsen
Senior Researcher
Centre for Oil and Gas - DTU
+45 45 25 72 37

Contact

Alexander Shapiro
Associate Professor
DTU Chemical Engineering
+45 45 25 28 81