A method and apparatus useful to determine the integrity of a cement bond log disposed in the annular space between a casing and a wellbore. The method and apparatus induce a Lamb wave in the casing and into the wellbore. The Lamb wave attenuates upon passage through the cement bond log. The integrity of the cement bond log can be determined through an analysis and evaluation of the attenuation results.

A method for determining whether cement (68) in a well bore hole (40) has cured comprises positioning at least one temperature sensor on an exterior surface of a well casing; placing cement in an annulus between the well bore hole and the exterior surface of the well casing disposed in said well bore hole; and monitoring the temperature of the cement using the temperature sensor.

The invention provides a method for estimating an impedance of a material behind a casing wall, wherein the casing is disposed in a borehole drilled in a geological formation, and wherein a borehole fluid is filling said casing, the material being disposed in an annulus between said casing and said geological formation, said method using a logging tool positionable inside the casing and said method comprising: exciting a first acoustic wave in said casing by insonifying said casing with a first pulse, the first acoustic wave having a first mode that is either of a flexural mode or an extensional mode; receiving one or more echoes from said first acoustic wave, and producing a first signal; extracting from said first signal a first equation with two acoustic properties unknowns for respectively said material and said borehole fluid; exciting a second acoustic wave in said casing by insonifying said casing with a second pulse, the second acoustic wave having a thickness mode; receiving one or more echoes from said second acoustic wave, and producing a second signal; extracting from said second signal a second equation with said two acoustic properties unknowns; extracting the acoustic properties of said material behind the casing wall from said first and said second equations.

A method for collecting geological data ahead of a drill bit used in a well bore hole comprises attaching at least one acoustic sensor (88, 90, 92) to a surface of a portion of casing; positioning the at least one acoustic sensor and portion of well casing in a well bore hole; using a drill bit and drill string to drill a section of well bore hole below a distal end of the section of well casing disposed in the well; generating an acoustic signal with an acoustic generator (92) disposed in the drill string; and receiving said signal with said at least one sensor attached to the well casing.

A method and device for imaging a description of a zone behind a casing of a well uses a logging tool provided with a plurality of acoustic transducers. The casing is insonified with a first acoustic wave using a first acoustic transducer for transmitting among the plurality of acoustic transducers. The first acoustic wave has a first mode that may be any mode of a set of modes defined as follows: extensional mode, thickness mode, flexural mode. A first acoustic transducer for receiving is selected among the plurality of transducers, a first echo is received at the first acoustic transducer for receiving, and a first signal is produced. A first measurement is extracted from the first signal. The method further comprises insonifying the casing with a second acoustic wave using a second transducer for transmitting, operating in a second mode that may be any mode of the set of modes but is distinct from the first mode. A second echo is received at a selected second acoustic transducer for receiving and a second signal is produced. A second measurement is extracted from the second signal. The description of the zone behind the casing of the well is evaluated from a combination of the first measurement and the second measurement.

A casing data relay for use in an environment including a casing (82,84) in a borehole (40), a first controller (116) for positioning in the borehole, and surface equipment (94) for communicating with the first controller (116), comprises a second controller (102) for positioning in the borehole and for relaying at least a portion of the communications between the surface equipment (94) and the first controller (116).

The relay may further comprise a third controller (100) for relaying at least a portion of the communications among two or more of the surface equipment (94), the second controller (102) and the first controller (116).

A method for maintaining the integrity of a formation (70) in the vicinity of a casing shoe disposed in a well bore hole (40) comprises measuring well bore hole pressure proximal to the casing shoe (54) during drilling of portions of the well bore (40) below the casing shoe (54) using at least one sensor (88, 90, 92) attached to an exterior surface of the casing shoe disposed proximal to the well bore hole; transmitting the pressure data measured by said at least one sensor to the surface and controlling the specific gravity of a drilling fluid being used in the well bore hole to ensure that the hydraulic pressure exerted by the drilling fluid does not exceed the fracture pressure of the formation.