There are limited experimental works have been recently done to test the effectiveness of ZnO nano-materials to change some characteristics of petroleum reservoirs.  For instance, ZnO may result in significant change the wettability of a carbonate reservoir rock from oil-wet alter to water-wet leading to decrease water cut and enhance oil recovery, as shown in the attached paper link.

http://www.scientific.net/JNanoR.26.9

https://www.onepetro.org/conference-paper/SPE-160847-MS

There are limited experimental works have been recently done to test the effectiveness of ZnO nano-materials to change some characteristics of petroleum reservoirs.  For instance, ZnO may result in significant change the wettability of a carbonate reservoir rock from oil-wet alter to water-wet leading to decrease water cut and enhance oil recovery, as shown in the attached paper link.

http://www.scientific.net/JNanoR.26.9

https://www.onepetro.org/conference-paper/SPE-160847-MS

 An interesting experiment;

Novel enhanced oil recovery method using dielectric zinc oxide nanoparticles activated by electromagnetic waves

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6136450&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6136450

http://www.sciencedirect.com/science/article/pii/S0921510706006672

I believe it can have good application with high H2S contained reservoir, either with drilling fluid or in-reservoir injection along with WF for example. You can't find many work published on this point, but I believe it is worth the investigation.

Abdelrahman