Methods and apparatus for harvesting potential energy downhole

An apparatus, comprising:

• a downhole oilfield system, the downhole oilfield system comprising:
• a conveyance;
• a downhole tool attached to the conveyance, the downhole tool comprising;
• a work performing module;
• a potential energy harvesting device configured to convert and store potential energy as a result of lowering or raising the downhole tool in a well;
• and
• wherein the potential energy harvesting device comprises a first plurality of rotation inducing angled wheels and a second plurality of rotation inducing angled wheels oriented in opposing directions configured to contact and roll along a well wall;
• the first and second plurality of rotation inducing angled wheels imparting an opposing rotation spin to regions of the energy harvesting device;
• and
• an energy storage module operatively connected to the regions of opposing rotation and harvesting energy from the relative rotation between the regions of opposing rotation.