Autonomous Well Logging Robot with Passive Locomotion

Downhole tools used in the oil and gas industry are usually controlled by an operator and tethered to the surface equipment via a few kilometers of long steel cable. Due to the total weight and volume of this steel cable, operating downhole tools requires a truck for transportation, winch, crane, and lubricator for placing into a well, and full time supervision by a trained crew. The large footprint of the operations brings time and cost inefficiency even when the task can be as simple as measuring the pressure and temperature downhole. There is a big opportunity to apply robotics and automation technologies to increase the efficiency of wellsite operations. Currently, robots have limited use in downhole applications mainly because of harsh environment and challenging working space. There are a number of robotic extensions designed as attachments to the tethered tools that can work semi-autonomously. By means of miniaturization and automation, it's possible to make an untethered downhole robot that can significantly reduce the operation footprint and increase time and cost efficiency. Here, we show a miniature untethered well logging robot that can autonomously travel and measure temperature and pressure. A key to miniaturization was to reduce energy consumption. Robots use their energy storage predominantly for locomotion. We exploited potential energies arising from gravity and buoyancy for the passively moving the robot inside vertical wells. We investigated the passive locomotion design considerations to avoid downhole obstacles.