Abstract: A detector assembly and methods including a magnetoresistive sensor capable of detecting anomalies in the wall of a casing string disposed in a wellbore. Examples of anomalies include gaps between casings such as due to casing joints, air gaps in casing threads such as due to flush casing joints, enlarged casing wall thickness such as due to external casing collars, damaged casing, perforations, and other discontinuities or deformities in the casing. The detector assembly and methods detect perturbations in the earth's magnetic field caused by the anomalies. The detector assembly generates essentially no magnetic or electromagnetic field so that other downhole instrumentation is not affected by its presence.

Abstract: A detector assembly and methods including a magnetoresistive sensor capable of detecting anomalies in the wall of a casing string disposed in a wellbore. Examples of anomalies include gaps between casings such as due to casing joints, air gaps in casing threads such as due to flush casing joints, enlarged casing wall thickness such as due to external casing collars, damaged casing, perforations, and other discontinuities or deformities in the casing. The detector assembly and methods detect perturbations in the earth's magnetic field caused by the anomalies. The detector assembly generates essentially no magnetic or electromagnetic field so that other downhole instrumentation is not affected by its presence.

Abstract: A detector assembly and methods including a magnetoresistive sensor capable of detecting anomalies in the wall of a casing string disposed in a wellbore. Examples of anomalies include gaps between casings such as due to casing joints, air gaps in casing threads such as due to flush casing joints, enlarged casing wall thickness such as due to external casing collars, damaged casing, perforations, and other discontinuities or deformities in the casing. The detector assembly and methods detect perturbations in the earth's magnetic field caused by the anomalies. The detector assembly generates essentially no magnetic or electromagnetic field so that other downhole instrumentation is not affected by its presence.

Abstract: A detector assembly and methods including a magnetoresistive sensor capable of detecting anomalies in the wall of a casing string disposed in a wellbore. Examples of anomalies include gaps between casings such as due to casing joints, air gaps in casing threads such as due to flush casing joints, enlarged casing wall thickness such as due to external casing collars, damaged casing, perforations, and other discontinuities or deformities in the casing. The detector assembly and methods detect perturbations in the earth's magnetic field caused by the anomalies. The detector assembly generates essentially no magnetic or electromagnetic field so that other downhole instrumentation is not affected by its presence.

Abstract: A casing joint locator device and methods of use are described. The locator device includes a giant magnetoresistive (GMR) sensor that is capable of detecting joints between sections of casing in a wellbore. The methods and devices described detect perturbations in the earth's magnetic field caused by air gaps and discontinuities associated with a casing joint or with an external casing joint collar. As a result, they are capable of detecting flush and standard collared joints. The casing joint locator generates essentially no magnetic or electromagnetic field so that other downhole instrumentation is not affected by its presence.

Abstract: A sensor assembly including a sensor mounted on the piston and a transmitter mounted on either the piston or cylinder. Preferably the transmitter includes a wheel which engages the wall of the cylinder so as to rotate as the piston reciprocates within the cylinder. The wheel includes one or more magnets which emit a magnetic field that is received by the sensor as the wheel rotates whereby the sensor provides a signal indicative of the rotation of the wheel. The sensor then sends the signal to a logic component which determines the direction, travel and position of the piston within the cylinder.

Abstract: The invention is a stationary radiation detection tool that provides an azimuthal indication of the location of subterranean radiation sources. In one embodiment, the tool has four gamma ray sondes, each of which receives gamma rays from a discrete sector of surrounding formation.