Is it feasible to use depleted oil wells for geothermal production?
In most cases, probably not.

Oil could be considered a metamorphic mineral, formed by "gentle" heating. That is gently on a geological scale - still enough to burn your hands!

Geothermal systems work most efficiently with a large temperature difference (Third Law of Thermodynamics). As soon as the temperatures increase enough to be interesting from a geothermal perspective, you are quickly losing ("overcooking") the oil on a geological timescale. 

Therefore most oil fields have had the heat applied in the past and it has since been removed. 
However this does not discount the situation where an oil field is still technically "being made" and the hydrocarbons are still being heated, and we just happened to drill it at just the right time. Hence the "in most cases": You might find the odd field where it is practical.

An old field, especially gas ones, could be used for carbon sequestration though. The field has stored methane for 10s if not 100s million years, why not the heavier CO2 instead?