DEVICE AND METHOD FOR MEASUREMENT BY GUIDED WAVES ON A METAL STRING IN A WELL

摘要

Device for detection of changes of resistivity or dielectrical properties due to changes of fluid compositions in the near-well area 0-500 m about a well (1) in a geological formation (9), comprising an electrically conductive tubing string (4), e.g. a liner pipe or an other fixedly arranged tube or openhole completion in the well (1). The characteristic by the invention is: a) an electrical energy source (24); b) a signal generator (22) for generation of electromagnetic signals (25) to; c) at least one transmitter antenna (2) for electromagnetic waves (26), arranged preferably above an oil/water contact, on a fixed first position on the tubing string (4), and arranged for essentially to guide the electromagnetic waves along the tubing string (4); d) one or more receiver antennas (8>1<, 8>2<, .., 8>n<) for guided electromagnetic waves along the tubing string (4), arranged on other fixed positions along the tubing string (4); e) devices (80) for receiving of signals (85>1<, 85>2<, .. 85>n<) induced in the receiver antennas (8>1<, 8>2<, .., 8>n<) due to wave impedance gradients along the tubing string (4) in rocks or fluids in the geological formation (9) and in the electrically conductive tubing string (4); f) signal processing means (82) for processing of the received signals (85>1<, 85>2<, .., 85>n<); g) communication devices (100, 200) for transmission of signals (105) representing the electrical signals (85>1<, 85>2<, .., 85>n<), and for receiving control signals (205).