Abstract: A method for determining a profile of a wall of a wellbore drilled through earth formations. The earth formations are irradiated by a source of gamma rays. Scattered gamma rays are detected at axially spaced apart locations from the source. At least one of the axially spaced apart locations is positioned on an opposite side of the source from the other ones of the spaced apart locations. A function, related to a rate of detecting the scattered gamma rays at a first one of the spaced apart locations with respect the rate of detecting scattered gamma rays at the at least one spaced apart location positioned on the opposite side of the source is calculated. Density of the earth formations, density of the fluid in the wellbore, and a difference between the densities is determined. An area bounded by the function is determined. The area is scaled with respect to the difference between the densities, and the profile is calculated from the scaled area bounded by the function.

Abstract: A method of measuring the density of an earth formation penetrated by a wellbore. The method includes irradiating the earth formation with gamma rays from a source, detecting Compton scattered gamma rays at a plurality of locations spaced apart from the source along the wellbore, calculating an apparent density of the formation from the detected gamma counting rate at each of the locations, calculating differences in apparent density between pairs of the apparent densities, calculating a correction for the apparent density from a distal one of the locations by scaling the differences in apparent density according to an empirical relationship, and calculating the density by combining the correction with the apparent density from the distal one of the locations.

Abstract: A method for determining density of a formation. The method includes irradiating the formation with gamma rays having energy consistent with Compton scattering. Gamma rays are measured at axially spaced apart locations. Two of the axially spaced apart locations are at an equal distance and in opposite directions relative to the source of gamma rays. The distance is smaller than the spacing of another one of the spaced apart locations. An apparent density for each spaced apart location is determined from the counts. Differences are calculated in apparent density between each one of the spaced apart locations, and a correction factor is determined for apparent density at each spaced apart location, thereby determining the density of the earth formation. In a preferred embodiment, determining correction factors is performed by a neural network using the differences in apparent density as an input vector.

Abstract: A method and device for measuring peak gamma radiation is provided wherein the method includes the steps of determining a minimum and maximum number of counts within a preselected multiple channel energy spectrum measurement range, determining a channel having approximately one-half the number of maximum counts, determining a channel representing a background energy, computing a peak energy centroid channel, computing a channel to energy conversion factor and recomputing the boundry channels for the preselected multiple channel energy spectrum measurement range.