Abstract: A technique for measuring the density and a lithology-dependent factor, compensated for borehole effects, with a gamma ray logging source and one or more gamma ray detectors has been disclosed. Other borehole variables are also measured and used as quality indicators. The technique uses the spectral information from the detected gamma rays to calculate all of the unspecified variables relevant to the measurement. This technique also allows a lithology-dependent parameter based on the short-spaced detector to be compensated for borehole effects without contaminating the measurement with lesser-quality data from a detector spaced further from the source. Furthermore, it allows multiple measurements of a lithology-dependent factor made with multiple detectors to be compensated separately. The multiple compensated measurements can then be combined to form a quantity which indicates the quality of the measurement.

Abstract: A method and apparatus for determining the extent of defects in ferromagnetic tubular elements comprising a continuous string for use in an oil or gas well is disclosed. The tubing trip tool measures tubing average wall thickness, local defects, such as corrosion pitting, and axial defects, such as sucker rod wear during removal of the tubing from the well. Tubing velocity is also measured, and couplings between tubing sections are detected and counted, in order to specify the axial location of defects on each tube, and also provide a profile of the condition of the overall string. A saturating magnetic field and a fluctuating magnetic field are applied to the tubing and the magnitude of the induced fields and the changes are measured to quantify defects in the tubing.

Abstract: A method and apparatus for determining the extent of defects in ferrogmagnetic elements, such as tubing comprising a continuous string for use in an oil or gas well is disclosed. The tubing trip tool measures the depth of local defects, such as corrosion pitting, during removal of the tubing from the well. Tubing velocity is also measured, and couplings between tubing sections are detected and counted, in order to specify the axial location of defects on each tube, and also provide a profile of the condition of the overall string. A saturating magnetic field is applied to the tubing and a comparison of two derivatives of flux leakage is made to quantify defects in the tubing.

Abstract: A tubing trip tool for use in determining the extent of defects in tubular elements comprising a continuous string used in a subterranean oil or gas well during removal of the string from the well is disclosed. Local defects and axially extending defects, as well as the average wall thickness of the tubular elements, are measured. The position of the defects is determined by measuring the variable velocity of the tubular elements as they are removed from the well. A noncontact velocity detector comprises detector elements generating a first signal dependent upon an applied magnetic field and the velocity of the tubular elements. The first signal is compared to a signal dependent only upon the magnetic field generated in a second element. A pickup coil and Hall effect probes can be used.

Abstract: A tubing trip tool for use in determining the extent of defects in tubular elements comprising a continuous string used in a subterranean oil or gas well during removal of the string from the well is disclosed. Local defects and axially extending defects, as well as the average wall thickness of the tubular elements, are measured. The position of the defects is determined by measuring the variable velocity of the tubular elements as they are removed from the well. A noncontact axial velocity detector comprises detector elements generating a first signal dependent upon an applied magnetic field and the axial velocity of the tubular elements. The first signal is compared to a signal dependent only upon the magnetic field generated in a second element. A pickup coil and Hall effect probes can be used.