I created a fork that fixes this issue simply by offering a boolean in the settings to not call the on_chunk_load event handler. It'd be awesome if either your project could do the same, or when the Map settings for deep sea oil is turned to "None" it will cause the event handler to never be called.

Seems SeaBlock removes the entities altogether, which causes problems in other areas and honestly is moreover their issue to fix as far as I can tell, but it'd be nice if your mod could accommodate it until SeaBlock addresses deleting things in a safer manner or someone creates an alternative to SeaBlock. I'm reading through wiki and such to discover better ways to handle this, until then here's my fork that addresses the issue as far as I've tested. When it's solved I'll deprecate it of course as I don't want people thinking this is my project: https://mods.factorio.com/mod/cargo-ships-seraph