Abstract: There is disclosed in one implementation a method of or for use in or for detecting, measuring and/or determining at least one variable or characteristic in a space, such as a well, container or vessel. In one implementation the method comprises: transmitting a first electromagnetic signal from a first position to a feature within the space; receiving a second electromagnetic signal at a second position after reflection of the transmitted first electromagnetic signal from the feature; transmitting a third electromagnetic signal from a third position to a calibration feature within the space; receiving a fourth electromagnetic signal at a fourth position after reflection of the transmitted third electromagnetic signal from the calibration feature.

Abstract: There is disclosed an apparatus (115) for detecting and/or measuring a downhole feature (195), such as a fluid/fluid interface, in a well (105). The apparatus (115) comprises a first fluid and/or liquid permeable tube (120). The first tube (120) is porous or (micro)perforated. The apparatus (115) comprises a second fluid and/or liquid impermeable tube (130). The first and second tubes (110, 130) are hollow, and therefore, provide first and second waveguides, respectively.

Abstract: A method for use in or for detecting a downhole feature in a well comprises transmitting an electromagnetic signal from a first position located substantially at or adjacent to surface through a first space to the downhole feature. The method further comprises receiving an electromagnetic signal at a second position located substantially at or adjacent to surface after reflection of the transmitted electromagnetic signal from the downhole feature and after propagation of the reflected electromagnetic signal through a second space. The method may comprise sealing the well before transmitting the electromagnetic signal. Such a method may be used to detector determine a distance from surface to a downhole feature such as a fluid interface in a completed production, injection or observation well.

Abstract: A structure defines an elongate space and comprises an apparatus installed within the structure. The apparatus includes a signal generator and detector arrangement, and at least one antenna coupled to the signal generator and detector arrangement. The at least one antenna is coupled to the elongate space for transmitting an electromagnetic signal into the elongate space and for receiving the electromagnetic signal from the elongate space after reflection of the electromagnetic signal from a feature within the elongate space. The apparatus may be used to monitor the feature within the elongate space.

Abstract: A system and method of data acquisition and transmission for use in a channel for conveying liquid and/or gas, such as a wellbore. The system includes one or more of data acquisition modules for acquiring data relating to conditions adjacent the module and transmitting the data to a terminal collection station or adjacent data acquisition module via an electromagnetic signal. Each data acquisition module is configured to transmit the signal such that an element of the channel adjacent the data acquisition module acts as a waveguide.