CRJ 900 First Officer reported loss of oil pressure in one engine and return to departure airport.

Narrative

We got to the airplane; ran all of our first flight of day checklists and walk around; everything was normal. Pushed back from the gate started both engines first flight of day. Began our taxi to the runway saw the Captain check fluid levels as I had seen him do on all of our flights things seemed normal. We took off and during climb he checked fluids again (as he usually does). As we leveled out at 13;000ft he asked me to help keep an eye on the oil fluid levels as they seemed to be decreasing. Shortly after; I had noticed the levels at around 46 percent on the right engine. We continued for a short period of time. In that time the levels continued to drop off fast. We called ZZZ center and asked to return to ZZZ due to oil levels. They cleared us direct to the airport. At this point we had not declared an emergency as oil pressure was still normal. At this point we have been talking to flight attendants and passengers. The Captain also sent a message to dispatch. We were also working on setting up the approach; receiving performance numbers and completing other required tasks. We were now talking to ZZZ approach and the oil level continued to drop to around 24 percent we [requested priority handling] and started our decent with vectors for the visual approach into runway XXR. After we joined final and began our final decent; after crossing the final approach fix for the runway oil pressure dropped into the red and we received a warning for R ENG OIL PRESS. The Captain called for the QRH R ENG OIL PRESS checklist. We initially began to run it but given our close proximity; to the runway we decided to focus on getting the aircraft safely on the ground. After coming to a complete stop on the runway we completed the R ENG OIL PRESS checklist and the engine shutdown in flight checklist (low oil pressure directed us to QRH engine shutdown in-flight) we completed the items on the checklist; shut down the right engine and then began our taxi back to the gate after communicating with the flight attendants again. We arrived back to the gate and talked to fire command who had met us on the runway and they had done a walk around of the aircraft at the gate. We were also told by maintenance that there was around 2 quarts of oil on the ground after parking back at the gate.