Abstract: A method and apparatus for logging downhole earth formations which converts, for a given logging tool geometry, a measurement of the extent of energy degradation of the spectrum of gamma rays emitted from a source in the tool and Compton scattered by the formation back to the tool, into a measurement of the density of the formation.

Abstract: The disclosure relates to a well logging method which is capable of providing an indication of salinity and water fraction of the production fluid of a borehole. This indication of borehole parameters may be obtained through the use of a conventional gamma ray logging system that detects gamma rays produced by isotopes created from neutron activation of oxygen, sodium, and chlorine that may be present in the production fluid. A logging sonde is passed twice through a portion of interest in the borehole at two different logging speeds. The fluid velocity relative to the sonde may be determined using these two logging speeds and a displacement distance which reflects the time required for a detector associated with the sonde to reach fluid activated by neutrons produced by the sonde.

Abstract: Naturally occurring gamma radiations from earth formations in the vicinity of a well borehole are detected and spectrally separated into six energy regions or bands. Borehole compensation techniques are applied to the gamma ray spectra and the attenuation coefficient .eta. is determined as a result thereof. The attenuation coefficient is used along with predetermined borehole, casing and cement parameters to derive a measure of the density of the earth formations.

Abstract: A method for measuring the location, linear flow rate, and volume flow rate of undesired water flow behind well casing in a well includes irradiating borehole environs with high energy neutrons from a neutron source located in a well tool in the borehole. Gamma rays from the decay of an unstable isotope which comprises a portion of any undesired behind casing flow present are detected with gamma ray detectors located in the well logging tool. Count signals representative of the detected gamma rays from at least one of the detectors are separated into at least three energy dependent signals. A ratio signal corresponding to the ratio of at least two of the three energy dependent signals is generated and an indication of the linear flow rate of the undesired behind casing water flow in a preferred direction is determined from the count signals from the detectors and from the first predetermined relationship.

Abstract: This invention relates to a logging tool housing construction for use with gamma ray logging devices. The tool housing is constructed of materials designed for maximum transmission of low energy natural gamma ray energies (E=150-300 Kev). The housing material which encloses a gamma ray detector is a tubular, filament wound graphite composition and has a tubular metal sleeve for wear protection. The core and tubular metal sleeve are constructed and interconnected to meet mechanical and pressure requirements for oil well logging use.

Abstract: In the preferred and illustrated embodiment taught herein, method steps for monitoring of raw materials to be used in drilling mud are disclosed. The materials are monitored for radioactivity. Procedures for taking such measurements are disclosed, and the extent of gamma radioactivity in the raw materials used in drilling mud is determined. This is correlated to the increased radiation attributable to mud made from these materials and the effect the mud would have on gamma ray measuring logs. An alternate procedure for testing drilling mud, typically at the well site, is also disclosed. The method detects mud radioactivity from any additives including barite, potassium chloride, well cuttings or others. Excessive background levels due to mud gamma radioactivity in a well may very well mask the data obtained by various logging procedures dependent on gamma radiation. Procedures are also described for either rejecting mud which is too radioactive or correcting the log measurements for mud effects.

Abstract: Natural gamma radiation is detected by a scintillation detector in a well logging sonde and separated into at least six separate energy regions. The gamma ray counts in the higher four energy regions are used to derive borehole compensated elemental concentrations of potassium, uranium and thorium. The gamma ray counts lower two energy regions are used to identify formation lithology.

Abstract: This invention relates to an improved method for determining the oil saturation of subsurface earth formations in the vicinity of a well borehole. High energy neutrons irradiate the subsurface earth formations and gamma rays caused by inelastic scatter with the subsurface earth formation constituent materials are measured. For a chosen borehole depth, gamma ray logs are taken in different situations: first, with the formation fluid water and oil mixture in an undisturbed state; second, after flushing the formation with alcohol to displace the formation water and oil mixture; and, finally, after flushing the alcohol from the formation with water to obtain a measurement with no oil in the formation. The gamma ray measurements obtained are then used to determine the oil saturation without requiring knowledge of the porosity of the earth formation, borehole conditions or formation type.

Abstract: A method of well logging utilizing naturally occurring gamma radiation is disclosed. In the preferred and illustrated embodiment, the thickness of the casing in a well borehole is measured. The photoelectric absorption of gamma rays from the formation by the iron in the casing varies as a function of the energy of the gamma radiation. The detected gamma spectrum below about 350 KeV from the surrounding earth formation is preferably divided into two energy ranges or windows, and a ratio between the two to indicate the thickness of any intervening steel casing material. With suitable scale factors in calibration of the system, casing thickness can be determined from the ratio of the summed naturally occurring gamma count rate in the range of about 35 to about 120 KeV divided by the count rate in a higher energy range from about 180-325 KeV.

Abstract: Methods and apparatus are provided for making improved pulsed neutron derived measurements of the carbon: oxygen ratio in subsurface earth formations. Plural radiation measurements are made as a function of time from the initiation of the neutron pulse to distinguish inelastic and thermal neutron interactions. These measurements are then combined in several different manners to provide an improved carbon:oxygen ratio measurement and multiple porosity and formation lithology indication measurements.

Abstract: A gain stabilized natural gamma ray spectroscopy system is used to measure casing thickness in a cased well borehole. A ratio of gamma ray intensity in two selected energy ranges forms a measurement signal representative of casing thickness based on the photoelectric absorption of natural gamma rays by iron. A coincidence technique employing dual scintillation crystals and a stabilization source of charged particles and known energy gamma rays is used for gain stabilization.

Abstract: A natural gamma ray logging system utilizes gamma ray spectroscopy to measure thorium, uranium and potassium content of earth formations adjacent a well borehole. An additional measurement is also taken from which compensation for borehole effects on the measurements of interest is achieved.

Abstract: A method of logging earth formations to ascertain relative elemental abundancies of potassium (K), uranium (U) and thorium (T) is disclosed. A natural gamma ray spectrum of an unknown borehole is compared with individual standard gamma ray spectra of potassium, uranium and thorium in at least four energy ranges or bands. Decay peaks of the three elements are encompassed by three of the energy bands and at least one other energy band is used to monitor the changes in shape of the unknown spectrum caused by borehole conditions differing from that of the standard or calibration boreholes. A function derived from the gamma ray count rates in the four bands is used to compensate the elemental abundancies of the three elements to be detected in the unknown spectrum for the effects of differing borehole conditions in the unknown borehole from the standard borehole conditions.

Abstract: The present invention concerns methods for measuring simultaneously the formation and borehole components of thermal neutron lifetime as decay time. The borehole and formation are irradiated with pulsed 14 MEV neutrons. During the interval between neutron pulses the capture gamma radiation is measured in at least four, non-overlapping, contiguous time gates. A background radiation measurement is also periodically made. The background corrected capture gamma radiation measurements are combined to derive simultaneously, the formation and borehole neutron lifetime components which are then recorded as a function of borehole depth.

Abstract: A method is disclosed for simultaneous determination of borehole and formation thermal neutron decay time components. The methods employ pulsed high energy neutron sources and time gated dual spaced detectors. Exponential decay curves are assumed for each of the components and iterative least squares fitting employing rapid convergence techniques are utilized.

Abstract: Methods and apparatus are provided for making improved pulsed neutron derived measurements of the carbon: oxygen ratio in subsurface earth formations. Plural radiation measurements are made as a function of time from the initiation of the neutron pulse to distinguish inelastic and thermal neutron interactions. These measurements are then combined in several different manners to provide an improved carbon:oxygen ratio measurement and multiple porosity and formation lithology indication measurements.

Abstract: Earth formations surrounding a well borehole are bombarded with high energy neutrons which react with chemical elements in the formation components, giving rise to gamma radiation. The gamma radiation is detected by two separate, spaced detectors from which well logs are obtained indicating a ratio of the relative presence of silicon to oxygen in the formations.

Abstract: A well tool for developing measurements of pressure or temperature in a well bore comprising an elongated well tool which utilizes a coherent beam of light which is applied to the ends of separate fiber optics and the other ends of the fiber optics are detected to produce an electrical signal in response to differences between the outputs of the fiber optics to the detector. For measuring pressure, one fiber optic may be coiled in a temperature insulated chamber and sense a discrete sample from the earth formations while the other fiber optic is coiled in a temperature insulated reference pressure chamber. In another embodiment both fiber optics are subjected to pressure samples from longitudinally spaced locations of the earth formations. In still another embodiment, the fiber optics are subjected to the temperature in the bore hole at longitudinally spaced locations for obtaining a temperature gradient measurement.

Abstract: In situ measurement of the gas content of formation fluid using thermal expansion principles. The formation fluid from a wellbore source is passed through an expansion type valve into a test chamber. The temperature and pressure are measured upstream and downstream of the valve. The difference in the temperature measurement is an indicator of gas content in the formation fluid. Samples of the formation fluid can be taken on favorable indicators.

Abstract: A method for simultaneously measuring the formation bulk density and the thickness of casing in a cased well borehole is disclosed. Low energy gamma rays are emitted into the casing and formation in a cased borehole. Two longitudinally spaced detectors detect gamma rays scattered back into the borehole by the casing and surrounding earth materials. The count rate signals from the two detectors are appropriately combined according to predetermined relationships to produce the formation bulk density and the casing thickness, which are recorded as a function of borehole depth.