Is unpowered pumping feasible in a 20-meter deep well?

Not feasible. It takes some power to complete the pumping operation in deep wells. A 20-meter deep well is so deep that it is impossible without power. Pumping literally means pumping water from a low place to a high place with a power device, pumping water from a low place to a high place with a water pump, or pumping water to a place with atmospheric pressure.