This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 31149, “Sensor Ball: Autonomous, Intelligent Logging Platform,” by Erjola Buzi, Huseyin R. Seren, SPE, and Max Deffenbaugh, SPE, ASC, et al. The paper has not been peer reviewed. Copyright 2021 Offshore Technology Conference. Reproduced by permission.
The complete paper describes a method of retrieving downhole data that is a practical and inexpensive alternative to wireline or slickline logging and permanently installed sensors. The autonomous logging platform, called the Sensor Ball, is a handheld, untethered logging tool that one person can deploy and recover from a pressurized well with no special equipment or crew.
The tool is a battery-powered, self-deployed logging platform. A small dissolvable metal weight is attached to the housing magnetically and helps the free-fall of the tool in the well. Once a desired and programmed depth is reached, the tool releases the weight, and thus changes buoyancy and floats back to surface. Deployment and retrieval of the tool is safe and simple and requires only a wrench to open the cap of the wellhead but does not require cranes, logging trucks, lubricators, or blowout preventers. By sequentially opening and closing the cap, swab, and master valves, in just a few minutes, the untethered logging platform passes the wellhead section and begins traveling downhole. Retrieval is performed by reversing this process. As it travels down and up, the tool records temperature, pressure, and magnetic field data continuously in its internal memory. The recorded data are wirelessly retrieved once the tool is back at the surface.
A lightweight atmospheric housing provides buoyancy and insulates the electronics from the well fluids. While optimally exposing temperature and pressure sensors, the small body mass of the housing minimizes the temperature distortion in the downhole environment.
The tool is deployed and retrieved several times in the field. Downhole temperature, pressure, and magnetic field data are recorded for several hours. Without the need for field crew or personnel to stand by during the logging operation, rig-up and deployment times decrease from several hours to a few minutes.