In theory, yes. But I do not believe an oil field would be suitable. Hydro relies on a pressure difference. This means you want the turbine located at the lowe

In theory, yes. But I do not believe an oil field would be suitable. Hydro relies on a pressure difference. This means you want the turbine located at the lower reservoir, which is going to be tricky with an oil well. Oil fields are not a hole filled with oil but instead are just porous rock, which greatly limits the flow rate you can achieve from a single well. Oil fields are already pressurized, so you'd actually need to put in energy to get water in there. And of course you'd be contaminating the water with oil and gas, which makes the upper reservoir a bit of an issue.