I just want it to be somewhat believable. I don't want someone with knowledge of the industry to read it and think, "Ah, that's total B.S.
here's the problem
1. how exactly can this be done without anyone knowing it? You realize there is nearly 100% earth coverage by satellites 24/7. In the few hours where a particular area might be without coverage what could you get done? It takes days to rig up a normal onshore rig and it takes weeks to tow and set up a rig in the ocean.
2. how do you keep this secret for the amount of time needed? You couldn't possibly make something like this close to being somehow economic unless you are offtaking hundreds of thousands of bbls/day and have reserves in the order of 500 MMB to 1 GBbl so you are talking about having an operation undiscovered for something like a minimum of 5 years.
3. if this is disputed waters as you suggest there is no way in and out, any traffic on the surface would be noted immediately and ongoing sonar arrays would detect transport, construction and production noises on the seafloor. Disputed waters are generally well patroled as is evidenced from the continual warnings flying back and forth between China, Phillipines, Malaysia and Vietnam.
But yeah, lets magically transport a magical underwater facility that magically makes no noise or footprint while being setup and then magically keep it secret for a half decade. At that point using a magical laser (for what purpose I have no idea given it's not like you need a star wars system to make a hole) doesn't seem like a huge magical leap.
BTW I'm someone with 30+ years of hands-on knowledge of the industry. But once again, can't speak for your readership. My suggestion is just to give up on the idea of being able to convince oil and gas folks not to say "total B.S" . Even with films where the premise is completely historical and all the technology is pretty close industry folks tend to tear apart all the things that the film screwed up. Case in point being the film Deepwater Horizon.