It would only be warmer then the deep sea ocean temp (near freezing) if the oil was located closer to a significant section of magma. If the oil is located close to significant magma, why would anyone suggest using a nuke down there ?
If I'm not mistaken, deep wells (and 17,000 thru the crust is deep) have to use specially treated pipe in the drill stem because of the high heat that is encountered.
E.g., see this on the Homestake Mine.
The temperature of the rock at the bottom of the mine (8,000 ft) is 135 degrees F.