DETERMINING THE LEVEL OF A LIQUID IN A BOREHOLE FOR CONTROLLING OPERATION OF A SUBMERGED PUMP

A stand-alone apparatus for determining the level (X) of liquid (F) in oil boreholes (P) overcomes the need of a pressurized gas source. A loudspeaker-type electroacoustical transducer (11) both emits characteristic acoustical signals through the mouth of the borehole and detects the return of an echo from the surface of the liquid downhole for clocking the time-interval between emission and return to determine the level of the liquid. To overcome the limited power inherent in a loudspeaker-type transducer relative to masking borehole acoustic noise, a method of operation correlates the intensity amplitude of the detected echo with the emitted signal. Another solution comprises repeating emission and detection cycles a number of n times and then adding or integrating the n curves into a resulting curve which is filtered. The detected liquid level may be used for determining the submergence and regulating the speed of a pump in the borehole.