What products are available for oil and gas cleaning on an industrial scale? We want to get some for the future, in case there is a leak into production. I understand that you can't just buy such a product in a shop.

Your query doesn't sound very common and I don't think everyone will be able to answer you here. Therefore, I suggest you look for specialist websites that deal with the distribution of cleaning products for all surfaces. It must be something tailor-made. Here you can buy oil and gas degreaser https://ipax.com/product/emulsor/