Abstract: A seismic signal receiving system is provided for use in boreholes to receive seismic waves in carrying out geophysical investigations. The system includes three pairs of opposed plates, each of the pairs of plates including oppositely facing outer surfaces for engagement with opposite sides of a borehole. A seismic receiver is mounted on the inner surface of each of the plates for receiving seismic signals. A double-acting, fluid-operated actuator selectively causes relative movement of the plates of the pairs of plates away from each other to provide expansion thereof so as to enable the plates to engage the walls of a borehole and selectively causes relative movement of the plates of the pairs of plates toward each other to provide retraction thereof so as to enable the system to be removed from a borehole. The pairs of plates each comprise a relatively long plate and a relatively short plate. An expandable linkage interconnects the long plates at the distal ends thereof.

Abstract: In an in situ uranium leaching process, a method of detecting presence or absence of leach solution escaping from a desired leaching zone involves monitoring the electrical impedance of a zone just outside the desired zone to detect high ionic concentration indicative of leach solution. Electrical impedance is measured by locating monitor wells just outside the leaching zone and positioning pairs of current and voltage probes within the monitor wells and closest injection wells. Low frequency, constant current is generated by each pair of current probes between corresponding injection and monitor wells to develop a zone impedance-dependent voltage drop that is measured by each set of voltage probes and correlated to presence or absence of escaping leach solution. In an alternative embodiment, electrical impedances are measured between a single, central recovery well and a series of distributed, monitor wells to reduce the total number of probes required.