Miniaturized Casing Collar Locator for Small Downhole Robots

Despite advances in robotics for many harsh environments, the downhole environment is rarely accessed by robots. Small, autonomous robots for logging oil and gas wells potentially offer significant cost savings over conventional wireline logging tools, but there are some major technical challenges to overcome. Among these is navigation or how the robot can know its own position along the well. Oil and gas wells are lined with steel casing, made up of 40-ft-long pipe joints held together by threaded collars. The collar locations could potentially be used as features for navigation, but conventional magnetic casing collar locator (CCL) sensors are large and must be mechanically stabilized within the casing. This letter investigates the design of CCLs for small, untethered robots with limited energy resources.