Interfacial Tension and Wettability

1. If ultralow IFT could lead to enhanced oil recovery from fractured oil-wet carbonate cores, then, why the same is NOT true in liquid-rich shales @ lab-scale?

2. If wettability alteration to water-wet condition could enhance the oil recovery from oil-wet carbonates, then, why does wettability alteration to intermediate-wet condition (and NOT the wet condition) result in the highest oil recovery from water-wet sandstone cores @ lab-scale?

3. At the laboratory-scale, will it remain feasible to deduce the explicit roles/effects of IFT reduction and wettability alteration, when they both happen simultaneously?

4.  Will it remain feasible to conduct the experiments in the same core, one for investigating changes in IFT, and the other for investigating changes in wettability – in the absence of changing the restored saturation and wettability of the core?

5. In the presence of

(a) isolated oil droplets;

(b) oil film that adheres to pore-walls;

(c) residual oil in dead ends;

(d) residual oil in pore throats (oil ganglia);

(e) residual oil at pore corners;

(f) cluster residual oil; and

(g) trapped oil drops;

would it remain feasible to target explicitly on the above factors – based on, whether the reservoir remains to be either sandstone or carbonate; and based on whether the reservoir is water-wet/neutral-wet/oil-wet - towards implementing a successful EOR application @ field-scale?

6. To what extent, could we have control over the following forces 'individually' during an EOR implementation @ field-scale?

(a)          The pressure gradient generated by fluid injection (determined by the pressure difference between injection & production wells and their distance on a large scale as a function of reservoir heterogeneity) and in the presence of a significant change in flow pattern;

Can selective-plugging/polymer-addition lessen viscous fingering?

(b)         Gravity force (determined by the density difference between the injected water phase and the oil phase; and which forms a natural drainage);

Will it induce gravity override?

(c)           Capillary force (determined by the interfacial activities between rock, oil and injected fluid, whose magnitude and direction remain modified by the respective EOR technique)

When exactly will it aid the imbibition of injection fluid in order to efficiently displace residual oil?

(d)         Viscous force (the force between residual oil and the fluid flowing past the oil); Need to increase both injection velocity as well as the viscosity of the injection fluid?

(e)          Osmotic pressure (resulting from a high salinity contrast between the injected fluid and the formation brine)

Suresh Kumar Govindarajan

Professor (HAG)

IIT Madras

01-Sep-2024