1. Is it a semi sentient oil refinery or is it a company that sees people as a resource?
It's semi-sentient oil refinery that sees people as a resource and uses them as such. It's an allegory for companies that tend to dehumanize their workforce. There is no company per-se, though the Foundation has to create the facade of a company to conceal the anomalous nature of the facility.
2. How exactly it works and what happens to the employees
The "employees" are people lured in by the SCP and used as a resource. After initial "employment" they start out doing normal refinery work, but the SCP uses this work to gradually break the people down mentally. They become more and more devoted to their work, and begin to lose their humanity little by little. As this happens, they have to be isolated and policed by the Foundation because as their mental faculties are lost they begin to become more zombie-like in behaviour. They begin to see other employees as competition which results in conflict between employees that can result in serious injury or death without intervention. As they reach the end of this rabbit hole of madness, they begin to disregard basic things like food and water and their basic biology begins to change. This change in biology has two end results. Result 1: The employees become grotesque living human 'equipment' in the refinery and are integrated into the facility as things like pumps, pipes, and storage containers. Result 2: Their biology is altered in a way that makes them plant like and they die. Once dead, the facility breaks down their bodies and deposits the remains into a river delta. The remains mix with sediment from the river and settle at the bottom of the ocean. The refinery does this because this is how oil is formed in the first place: dead plant material mixes with sediment, settles, and becomes oil after a few million years.
3. The refinery needs to be placated to make it more docile/It's a logistical nightmare that requires a public facade.
The refinery requires resources to function. Aside from crude oil, a myriad of different chemicals and compounds are used in the production of oil. If the refinery is supplied with these resources, it is docile and more or less keeps to itself producing normal fuels. If it is not supplied with these resources, it will actively seek them out, often in ways that are destructive and not very subtle. This is how the SCP is initially discovered. An oil company finds that their pipelines have been tapped into by the SCP refinery. The refinery will also retaliate if it feels threatened. It does this by producing adulterated oil products such as diesel fuel that is explosive and causes cars to explode, or gasoline that releases toxic fumes too kill people it sees as threats, oil that destroys engines, etc. Destroying the refinery does nothing except agitate it and it will always rebuild itself. It doesn't actively harm Foundation personnel (or anyone besides "employees) who enter it so long as they don't interfere with the refinery's operations.
There is also the requirement for humans as well. However, the Foundation cannot simply keep supplying D-class personel as disposable people. It actively seeks out people with certain personality types as well as people who actually have experience in the oil industry. This is where the moral dilemmas come in because the Foundation has to find ways of making sure the refinery has a steady workforce, but this workforce is made up of innocent people. The Foundation attempt to minimize the social implications of this involuntary workforce. This requires the creation of a public facade to make the refinery and it's operations appear normal since it cannot be completely concealed.
The refinery also keeps track of the products it makes and will become aggressive if it senses that the Foundation is simply destroying the refined materials it produces. While a small percentage of the fuel and chemicals it makes can be safely destroyed, the majority of it must make it to the consumer market, otherwise the refinery will retaliate. This means that every thing made by the refinery must be tested and distributed. A small percentage of product (specifically adulterated products) are destroyed up to a certain percent threshold, after which the Foundation must find uses for products that aren't standard gasoline and diesel fuel. The distribution of the product is also handled by the Foundation to prevent the refinery from distributing the fuel itself. Without the Foundation handling distribution, the refinery would assign "employees" to distribute the fuel which is a bad thing as the "employees" are not always mentally sound and are a threat t the general public.
4:
I’ve done the same with my own scips, so I would advise you to keep making these connections as you're explaining how the SCP functions. Some ideas off the top of my head might include the SCP itself being a victim of extreme work culture: it too is a victim/manifestation of corporate greed, therefore it consumes and consumes and consumes, just like its human workers. A possible route you can consider.
This was pretty similar to the approach I wanted to take with this SCP, though, I am still kind of refining it (no pun intended) and figuring out how exactly I want it to play out, though you can probably see some of the framework in the above answers to your questions.
5: What is your plan for execution?
The refinery makes itself known when an oil company finds that their pipelines have been mysteriously tapped into. They find their oil pumps sabotaged or hijacked, and workers from their own refineries begin to disappear. Eventually they find the SCP refinery and instead of contacting the Foundation, the companies convince their respective governments to destroy the anomalous refinery. They do so, only to find out that the refinery quickly rebuilds itself and retaliates massively, adulterating huge quantities of fuel and hijacking and destroying other refineries and equipment. In over their heads, they finally decide to let the Foundation know about the SCP. This is where the initial exploration begins. The Foundation creates a cover story of an embargo (The 1973 Embargo specifically) as an initial way to control the situation while they try to figure out how to handle the situation. The Foundation explores the refinery and it's components thoroughly, finding the grotesque human equipment and learning about how it functions.
I was also thinking about including things such as the Exxon Valdez disaster or the Deepwater Horizon disaster as incidents caused by this SCP, though I haven't wrapped a narrative around those yet and am unsure if I should include those as well.
