Yes if you want to pay down a 30 year mortgage in only 15 years it certainly is very possible to do so assuming you have the money to pay down the 30 year mortgage sooner.
You can either refinance the mortgage from a 30 year mortgage to a 15 year mortgage but when you refinance the mortgage you'll have higher payments per month so make sure you can afford the extra payments on the 15 year mortgage versus the 30 year mortgage.
You can also just double up on the payments or triple the payments each month and it will pay down the mortgage much sooner in 15 years and sometimes less.
A friend had a 30 year mortgage and he paid the mortgage down in 10 years which was amazing since he was able to triple the payments each month on the mortgage.
By paying the mortgage down in 10 years he saved over $100,000.00 in interest on the mortgage which was a very good savings.
Now he puts the mortgage payments into a savings account and has a nice little retirement fund when he gets ready to retire in the years down the road.