pressure testing well casing

i have a 2" sandpoint about 50 ' deep is it possible to pressure check the 2" casing with air pressure to check for leaks or will it just push the water back out through the sandpoint theres about 15 to 20' of static water in the well

 

If you tried that, you would push the water back out to a point.
When the air pressure reached the same pressure as the water coming in it would just stop, the pressure would not go up or down.
Now that would also depend on the how good the grouted seal is between the earth and the casing. If there is a small leak there, the air and/or water would seep out beside the casing and out the top of the bore hole.