An Untethered Sensor Platform for Logging Vertical Wells

The measurement of fluid and rock properties within oil and gas wells is critical to efficient hydrocarbon production. These data are generally acquired by wireline logging, where sensors are lowered into the well at the end of a long cable. The handling of this cable adds significant cost to downhole data acquisition. In this paper, a proof of concept demonstration of an untethered sensor platform for logging vertical wells is presented. The platform is the size of a golf ball and works based on buoyancy change. The buoyant sensor housing and electronics initially holds a weight such that it sinks in the well. It releases the weight when it reaches a programmed depth and floats back up to the surface, logging data during the whole operation. The data are downloaded after retrieving the sensor. This miniaturized, tetherless platform can reduce the cost of logging operations and pave the way for semipermanent downhole sensors.