An 82 mm diameter downhole geothermal quadrant- by-quadrant flow tool (QFT) is under development in which any and all of the following four ultrasonic modes may be selected: transmission, reflection, tag correlation, and noise. The reason for employing ultrasonics is to obtain the required performance while avoiding the limits on other sensors caused by their use of moving parts, flow-restrictive orifices, or sensitive surfaces whose heat transfer properties are likely to degrade quickly in the hostile high-temperature (250 to 350ø C) downhole environment. A special advantage of ultrasonics is its ability to measure annular flow quadrant-by-quadrant. Such profile data could contribute uniquely toward understanding the orientation of downhole fissures. The reason for investigating as many as four modes in Phase I is that each is suited for only part of the flow range or flow conditions. From among several piezoelectric transducers whose critical temperature is 400ø C or higher, one must be selected that is most easily adapted to configurations required by the four modes. Ideally, several modes would share pairs of transducers. Tests of the nonelectronic portion of the flow tool will be conducted to 350ø C. At room temperature, annular flow system tests will be conducted quadrant-by-quadrant from 0.05 to 5 ft/s, a 100:1 range, in a 6 in. pipe. A commercially available electronic instrument already operates in multiple modes, but it needs to be repackaged in Phase II to meet the thermal, chemical, pressure, monoconductor, small diameter and other downhole requirements. The adaptability of the geothermal tool to oil and gas downhole exploration and logging, diagnostic leak detection and sensing of fissure orientation means that, if the QFT is successful in Phase I, private funding is likely to be forthcoming from industry.Anticipated Results/Potential Commercial Applications as described by the awardee: In Phase I an 82 mm diameter sensor will be demonstrated at temperatures up to 350ø C, and tested at room temperature using up to four different ultrasonic measuring modes. Using different algorithms but sharing transducers, each of these four modes is best suited to a particular part of the flow range or fluid conditions occurring downhole. Successful demonstration of these modes, three of which utilize coded transmission and correlation detection, should justify the Phase II continuation of the concept to the point of repackaging the entire tool (sensor and electronics) to meet downhole geothermal needs. Three direct spinoffs will be: (1) a diagnostic inspection tool for finding leaks in downhole conduits or joints; (2) a fissure orientation sensor; and (3) a logging tool for oil and gas exploration. These spinoffs are likely to motivate industry to co-sponsor sequels to this DOE project.Topic 1: Geothermal Instrumentation
