As far as skin care is concerned, oily skin is generally oily for one of two reasons, both start with the wrong cleanser.
If you wash oily skin with a lubriderm type cleanser, you will generally find that not only does'nt your skin feel clean after cleansing, it can also feel coated. Have you ever used this cleanser on your skin and gotten white oil filled tiny bumps with continued use?
If you strip oily skin by using a cleanser that is too harsh, you will find that your skin gets even oilier. When oil has been stripped from the skin, your skin will in turn produce more oil to make up for what is lacking. Before I was an esthetician, I used to make home made concoctions of some of the harshest "natural" skincare products I could make which only made my skin sensitive and greasy. It was not until I trained, to become an esthetician and learned how to correctly manage my oily skin that I found relief.
The best solution for controlling oily skin is to wash with a cleanser that emulsifies the excess oil, and washes it away with each use. A clay based mask used as directed can also help to sop up the excess oil (Imagine if you threw flour in a cup of oil, the flour would eventually become saturated with the excess oil, this is how masking with a good clay mask should work with oily skin).
As you control your oily skin the right way, expect for any issues with large pores to get better if not go away for good!