I had to think about that for a while. And after careful consideration, I would have to say yes. My reasoning is that, as I said in my previous post, manufacturing takes raw materials and processes them into a finished product. That process can have many steps. One step in that process is creating the tool(s) to do the actual processing, in this case engineering a refinery, so creation of those tools used in the manufacturing process is one step in the larger manufacturing picture. While the engineering itself is not a direct step in the manufacturing process, it does fall within the ripple effect that is needed to support manufacturing.
You are right. Without the engineers, there would be no refinery and no wealth creation.
What of the accountants who work for the oil company? Do they create wealth?