Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno

Alan Joseph Hunter

Arno Willem Frederik Volker

Mariana De Soares Silva E Melo Mota

A well bore is inspected to detect cement defects that can give rise to leakage. The well bore comprises an inner metal pipe. Outside the inner metal pipe its configuration may vary with distance from the top of the well bore in terms of concentric pipes outside the inner metal pipe and presence of cement between the pipes. A probe with is lowered through the inner metal pipe. An ultrasound signal is transmitted from the probe into the inner metal pipe and responses to the transmitted signal are received at a series of ultrasound receivers at different axial positions. A selection of a spatial frequency of waves arriving along the axial direction at the ultrasound receivers and/or the apparent velocity of said waves is retrieved dependent on the configuration. The received responses are band pass filtered accordingly. By selecting the band pass filter dependent on the configuration it becomes possible to detect cement defects well outside the innermost pipe from parameters of the earliest arriving pulse from the filtered reflection signal.

Method and a system for ultrasonic inspection of well bores

Improved imaging is provided for structures under test that have propagation direction dependent ultrasound propagation speed or position dependent ultrasound propagation speed due to fibrous, coarse grain or single crystalline material. A set reflection points is selected in the structure under test and ultrasound propagation time delays between the reflection point or points on one hand and the plurality of positions on the other hand that fit an observed time delay of the detected reflections are computed. This may be done by means of an iterative method. In the iterative method a synthetically focused ultrasound beam is realized by summing measurements after compensation for propagation time delay from different transmitting transducers to the reflection points. Time delays to receiving transducers are measured from the arrival time of reflections of this synthetically focused ultrasound beam, and the propagation time delay from different transmitting transducers is iteratively adapted until it matches time delays corresponding to the measured arrival times. Time delays to other points in the structure under test are interpolated between the selected reflection points and used in the computation of an image of reflections within the structure under test.

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's-Gravenhage, Netherlands

Alan Joseph Hunter