Abstract: Corrosion in well tubing strings, pipe and similar conduits may be determined by a circuit which includes a current sensitive meter and a known voltage source which is placed at selected intervals in the tubing string to make current flow measurements and voltage drop measurements between spaced apart contactors engaged with the tubing string at the selected intervals. The current flow measurements from the known source are used to determine resistance of the measured interval and voltage drop from a second source imposed on the tubing string at the surface is measured at the selected intervals to determine current flow from the second source. The differences in current flow at the selected intervals at a first measurement are compared with the differences in current flow at the same intervals at a later time to indicate any changes in current flow which may be related to corrosion in the tubing string between the intervals of measurement.

Abstract: Multiple gas lift valves interposed in a well tubing string are each configured to have gas flow ports adapted to emit a predetermined acoustic signal for transmission through the well to a microphone or similar acoustic signal receiver whereby a determination may be made of which gas lift valves are open or operating properly. One or more of the gas lift valves may also include fluid pressure, temperature and viscosity sensors as well as a valve opening sensor and/or valve pressure setting control and an associated signal controller/generator arrangement for generating signals for transmission to the surface. The signal generators may be of the acoustic or so-called stress wave type.