The shallow seismic that should have been done to clear the location before drilling would have picked up any shallow hydrocarbon accumulations. These are called shallow hazard surveys and we do them because shallow hydrocarbons are hard to manage before the pressure string / BOP is connected. They are almost always biogenic gas and fizzy water of little consequence. Shallow water flows on the other hand cause foundation problems but are not an environmental hazard.
So they must be monitoring the flow volume through the seep ? Or can they do that accurately ?