Untethered Well Logging Robot

H.R. Seren, E. Buzi, M.L. Zeglache, A. Bukhamseen, T. Hillman, T. Thiel, M. Deffenbaugh
Aramco Services Company,
United States

Keywords: well logging, autonomous vehicles, sensors, harsh environment


Most of the downhole tools used in the oil and gas industry are tethered and supervised by a user. Tethered downhole tools, such as wireline or slickline tools, require a few kilometers long cable that needs a truck to mobilize, additional tools such as winch, crane, and lubricator to place into a well, and fulltime supervision by a trained crew. All of these contribute to inefficient operations with a large footprint even when the task can be as simple as measuring the pressure and temperature downhole. As an alternative to these tools, some wells are instrumented with permanent sensors. These sensors can provide information continuously or on demand, but the initial investment can be costly, and they are not economical for every well. By means of miniaturization and automation, it’s possible to make untethered downhole robots to reduce the operation footprint and increase the time and cost efficiency of well logging. Here, we present an untethered, palm-sized well logging robot that can autonomously travel down and up in a liquid filled well, and measure temperature and pressure. The miniature robot is powered with coin cell batteries that provide a limited energy budget. This is mainly made possible by relying on gravity and buoyancy for locomotion. Briefly, it takes a weight to sink, and, at a desired depth, releases its weight to regain its buoyancy and returns to surface. During its round trip it logs temperature, pressure, and magnetic field data that are retrieved after the robot returns. Magnetic field data is used as a depth reference via recognition of casing joints whose depths are known from previous construction reports or wireline logs. The untethered well logging robot has been trialed in various water wells and temperature, pressure, and magnetic field logs have been successfully retrieved. Time spent to deploy and retrieve the robot was only a few minutes each time, freeing the field personnel for more important tasks. With an initial goal of replacing tethered temperature and pressure logging operations, the tool shows a promise to avail many future applications, particularly the ones based on miniaturized sensors. In this presentation, the features of the robot will be introduced, example field results will be shown, and potential future applications will be discussed.