Airbus Industrie Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Distraction; Time Pressure; Troubleshooting
Aircraft Equipment Problem Critical
Air Traffic Control Issued New Clearance; Flight Crew Landed in Emergency Condition
Aircraft
Autopilot 1 engaged. Passing 15 to 16;000 feet we noticed the right engine oil quantity began to decrease.  Captain was Pilot Flying and declared 'My aircraft' and I got the QRH in anticipation of an ECAM (Electronic Centralized Aircraft Monitor). We asked Center to stop climb at 23;000 feet in order to investigate our engine indications. The oil quantity decreased to zero and two amber X's appeared where oil quantity is usually read. No ECAM. We asked for a turn back. We leveled off at 23;000 feet and began a left turn. The right engine oil pressure then began fluctuating and decreasing. We swapped controls. I as Pilot Monitoring announced 'My aircraft and my radios.' The oil pressure on the right engine dropped to red indication and then immediately we got the master warning and shut down engine ECAM. The Captain followed ECAM. I declared 'MAYDAY' and advised Center we lost the right engine and asked for direct to a fix for an ILS approach.The Captain advised the flight attendants of the return and made a returning PA; advised Dispatch via ACARS of return; and did follow ups in QRH from the engine shut down ECAM. I was descending to 11;000 feet single engine on autopilot 1. Center did offer direct to one of the fixes along our route but we declined. We swapped controls again and Captain declared 'my aircraft.' Now as Pilot Monitoring I followed up with normal checklists.  The Captain flew an approach single engine and landed. We taxied to hard stand number 23 where airport personnel and Maintenance met us.
An air carrier pilot departing an airport reported shutting down one engine due to a oil leak and returning to their departure point.