| 摘要 |
The present invention is directed to an apparatus and method for obtaining azimuthally dependent measurements for evaluating the casing cement bond quality and, more particularly, for detecting and specifically locating channels or fissures between the casing and cement. The quality of the bond behind one or more arcs of known location on the casing is determinable by the present invention. The apparatus and method of the present invention employ a plurality of sonic transducers disposed in near contact with the casing in defined segmented locations about or around the exterior surface of a downhole tool. The transducers are arranged in a plurality of arrays, each array comprising four transducers, two transmitting and two receiving transducers, disposed along a single are about or around the exterior of the tool. The transducers are arranged so that two adjacent transducers in each array perform the same function in the array so that the bond quality between the similarly functioning and adjacent transducers is determined. The sets of arrays of transducers provide determinations in a continuous and complete loop around the casing. The casing cement bond quality is determined by measuring the attenuation of the compression wave from a pulsed acoustic wave traveling along the area of the helices. The apparatus and method of the present invention are also useful for making azimuthally dependent measurements in hard formations to detect fractures in uncased boreholes. When detecting fractures, the attenuation of the shear wave rather than the compression wave is measured. |
