2002 Nissan Quest Engine smokes

At starting the car in the morning, it emmits blue smoke it been static, but after a while and movement as started the smoke stops, I did ask my engine he said it was caused by oil, pls I want to confirm how true this is and if so, what type of oil can I use to service the engine after I drain it, is there any thing like oil treatment, if yes, can u prescribe any to be used to correct the smoke, because I check the plugs and discovered that the fir plugs are still very OK, none of them was soak of oil, so pls I will appreciate your time response to the mail.