**Acknowledgements**

*Nano- and Microencapsulation - Techniques and Applications*

• From FESEM photomicrographs, most of the silica nanoparticles aggregates observed at the outer section of the treated core that has been pushed out during brine post flush and some remains adsorbed inside the core showed as

*The average size of silica nanoparticles at fine, medium and coarse classification (a) during initial brine* 

• The particles size of core flooding effluents during silica nanoparticles are smaller that supported the high pressure drops value. In contrast, the particles size is much larger during brine post flush supported with low pressure drops value.

• In general, the permeability impairment after silica nanoparticles injection is insignificant and the silica nanoparticles concentration can be further optimized that can be beneficial as improved oil recovery agent with minimum risk

spherical shape with little aggregates.

*injection (b) brine post flush after 1 week aging.*

of formation damage.

**254**

**Figure 22.**

The author would like to thank Wan Shah Rizal Abdullah, Ms. Fatin Najihah Jasni, Ms. Nurul Syuhada M Sobri and Mr. Zulkarnain Harom, Ms. Afidah Sastro for their assistance in the laboratory. The use of equipment facilities at PETRONAS Research Sdn Bhd (under allocation E.025.JRD.02017.401) and support by Nazarbayev University (research funding ID: 080420FD1911) is gratefully acknowledged.
