You need to get the oil both West and North from the Maikop fields, let alone the ones on the Caspian Sea. Local use is ideal but you don't have that much need for that in the area once they are secured, you have other places that need the fuel also, remember oil is not just used by the aircraft, tanks and trucks on the Eastern Front. You have lots of need from the Bay of Biscay all the way to the front lines in the East and have to provide it in a timely manner.
Flying there to attack the area is not a problem because of the mountains. The 15th Airforce flew missions all the time to Austria, Central Germany and Northern Italy that crossed the different Alp ranges among others. You don't have to have a full airforce hitting the area, even bomber command with night mission should be able to find the area that is need to be hit. This is a classic area strategic attack and you would force the Luftwaffe to transfer their fighter aircraft to the area to defend it. Remember the Allies are adding more bombers a month than the Germans are adding fighers and pilots.