1986 911 Carrera fuel tank location

Vehicle Information: Model: 911; Year: 1986; Body Type: Convertible; Engine (type, size, modifications): 3.2; Total Mileage: 120000;

On my '86 911 Cab, there appears to be a reservoir type of structure between the left front fog light assembly and the left front wheel. After removing the fog lights, I drilled a few holes thru the fog light bracket to let air in and accidentally nicked the structure behind the fog light bracket that looks like a reservoir. The Bentley and owner's manuals do not specifically discuss this reservoir. Is it a reservoir, it it part of the fuel tank - what exactly is it? The nick is very minor, just a scratch by the drill bit. There was no leakage at all after the nick. After about an hour, I covered the nick with some body filler putty. Thanks