The Refueling Base mission appears in Chapter 3 where you will get the objective of destroying an energy refinery plant. If you move forward to complete this objective then you will miss the Refueling Base Combat Log. There are two Battle Logs in the region that can be obtained by killing two mechs. You can also grab the same by killing each and every enemy in the region. If you are not interested in putting much then read the locations of those NPCs below and collect the combat logs.
The main objective here is to locate two Mechs in the region who will drop the battle logs. The first one is below the bridge on the left side. As the mission begins follow the objective marker. It will take you to the edge of the mountain and after that, you can see a bridge.
Go down toward the end on the left of the bridge and you will spot an armed mech. Kill this one and collect the first battle log. Now there is one more similar. To find the second battle log, go left side, you will see two bridges.
Refer to the image above, this location is just below the bridge towards the left. Fly towards the first one and look at the platform on the right corner side. There is one mech and this one has the second battle log. Defeat the bot and you are done with collecting two combat logs from Armored Core 6. There is hardly anything left in the mission. Complete a few objectives ahead and you will be done with The Refueling Base mission.
Another way to grab all the combat logs is to kill each and every NPC flying around. This will be a time-consuming task, but it is for sure you will get all the AC6 collectibles. Or you can just grab two of them, play the main objectives, and move on to other chapters. To help you more with collectibles you can check the above link. This article has a list of all combat log locations in AC6’s different chapters. Also, you can find a lot of details on various trophies in the game.