Type t vent pipe tp chimey

This is the vent for an oil fired furnace that in my opinion close proximity to the chimney. I’m having issues finding much information on this type of pipe. Does anybody know if this location is okay?

I tried google and found ・Place the system at least 3’ (.9m) away from any other building opening, gas utility meter, service regulator or the like, or other distance if specified in the appliance’s instructions. Would you call this an opening?

No issue with the metal chimney clearance unless you saw evidence of backdraft. What was the masonry chimney used for?

Wood stove insert.