Air Carrier First Officer reported a possible fuel leak during climb; resulting in fuel imbalance. Flight crew returned to the departure airport and landed.

Narrative

In the climbout on the ZZZZZ Departure; passing about 17;000 ft.; Captain pointed out an ever-increasing fuel imbalance. We were watching the #2 main tank quantity dropping rapidly. The #1 Main fuel tank read approximately 8;500 pounds and the #2 tank read approximately 7;600 pounds and dropping. As we diagnosed the issue in the climb; we shortly thereafter; received the Fuel Imbalance Alert. I flew and ran the radio with ATC while Captain ran the checklists. We [requested priority handling] and I coordinated with ATC for a level off and a return to ZZZ. We ran the Fuel Leak Engine Checklist in the QRH; and shut down the #2 engine per the checklist. We coordinated for [Runway] XXR due to the long runway; accomplished a brake energy calculation; and I transferred the aircraft control over to Captain; to fly the ILS. We taxied clear. The Emergency Crew verified we looked good; and we taxied to the gate uneventfully. I feel like all outside parties handled the event admirably. ATC was very helpful. We had a lot of Crew coordination going on; so we had to tell ATC to stand by with providing them with amplifying information about souls on board and fuel remaining. I should have just told them that info upon first declaring the emergency instead of waiting until all checklists were completed.Fuel imbalance over 1;000 pounds leading to diagnosing a fuel leak; accomplishing the checklists; and returning to ZZZ.