Abstract: A neutron source in a well logging instrument is periodically pulsed and secondary radiations emanating from the irradiated formations are measured by a detector system. Circuitry is provided for establishing the points in time at which radiation is detected within a signal measurement time interval and generating a timing function relating to the time distribution of the detected pulses. Additionally, the total count rate for the detected pulses within the signal measurement interval and count rate of detected pulses within a background measurement time interval are processed to obtain a measurement of relative background intensity. The relative background intensity and a timing function for background only within the signal measurement interval are used to correct the timing function for total detected pulses to provide a timing function for only the exponential signal.

Abstract: Apparatus for indicating the location of casing joints or collars in a cased borehole utilizing a magnetic field. An electrical detector coil array is disposed within an elongated body member having a plurality of arm member equidistant thereabout. Each arm member carries a casing contact pad having a permanent magnet mounted therein. The expansion force exerted on the arm members and the maximum range of expansion are independently adjustable.

Abstract: A well logging instrument includes a body member supporting one or more arm members which may be biased outwardly against the sidewalls of the borehole. The arm members may be held in a closed position, adjacent the body member, during entry into a borehole by a heat sensitive retaining member. As the instrument is exposed to borehole temperature the heat sensitive retaining member will within a preselected temperature range release the arm member allowing the arm members to expand outwardly from the body member into contact with the sides of the borehole.

Abstract: An explosive safe/arm system for use in a perforating gun includes a selectively rotatable member mounted intermediate a detonator and a length of detonator cord. The rotatable member includes a transversely oriented bore which is selectively rotatable into and out of axial alignment with the detonator and the detonator cord. Mounted within the bore is an explosive element for transferring an explosive detonation wave from the detonator to the detonator cord when the bore is in axial alignment.

Abstract: A radioactive logging source carried by a logging tool injects gamma rays into the formation. A detector generates a pulse for each gamma ray incident upon the detector having an amplitude proportional to the gamma ray energy. Electrical signals corresponding to each such amplitude are delivered to the surface. These incident gamma rays originate from the formation as well as from a monitor source of gamma rays of known energy adjacent the detector. An energy peak from the gamma ray energy spectra transmitted to the surface corresponding to gamma rays of known energy from the monitor source is accurately identified. At the surface, the peak is tracked during the logging procedure and a control signal functionally related to observed monitor peak shifts generated and delivered to the logging tool. A control circuit alters magnitude of the high voltage supply providing power to the detector in response to the control signal.

Abstract: A plurality of formation resistivity logging data sets are generated along a borehole. From the data formation dip values are preliminarily determined at different elevations along the borehole. The dip values are combined for each borehole elevation of interest in a functional relationship utilizing a variable scatter parameter related to dip direction and magnitude variations whereby the resulting dip value at each elevation is taken as the corrected value. The variable scatter parameter may be selectively varied to produce variable representations as desired of formation dip, including visual representations. These variable representations may range from those excluding dip data points inconsistent with prevailing geological interpretation patterns and thereby exhibiting progressively less scatter to those representations including more available and possible dip values with scatter to be interpreted.

Abstract: In apparatus for investigating earth formations traversed by a borehole, improved methods and apparatus are provided for achieving dynamic range control of formation measurements. In one embodiment adapted to formation resistivity measurements, a well logging tool moving through a borehole emits a current into the adjacent earth formation, and a corresponding measurement voltage correlative to the resistivity is sampled at discrete elevations as the tool traverses the borehole. An average of these voltage measurements is formed. When the magnitude of this average exceeds or drops below a predetermined range, the magnitude of the survey voltage is decreased or increased respectively by a discrete amount.

Abstract: Apparatus is provided for collecting a plurality of samples of fluids in earth formations traversed by a well bore. The sampling apparatus includes an elongated body member adapted to carry an extensible and retractible fluid admitting probe which is selectively placed in sealing engagement with potentially producible earth formations. The fluid admitting probe is coupled to a fluid passage which is selectively placed into fluid communication with a fluid sample collection chamber. A selectively controllable pressure control system located in the fluid passage intermediate the fluid admitting probe and the sample collection chamber allows the flowing pressure within the formation fluid sample line to be maintained at any selected pressure level functionally related to hydrostatic pressure during fluid sample collection.

Abstract: An activation well logging method and apparatus for identifying and measuring the presence of vanadium in earth formations surrounding a borehole. A well logging instrument including a source of neutrons is used to irradiate formations for a period of time sufficient to activate vanadium. The gamma radiation emanating from the irradiated formations are detected by a scintillation detector having output pulses directly proportional to the energies of the incident gamma rays. The output pulses having energies characteristic of the element vanadium are separated and counted to provide indication of any vanadium present in the irradiated formations.

Abstract: In the representative embodiments of the new and improved methods and apparatus disclosed herein, a well logging instrument includes an elongated body member having a funnel configuration fluid collector mounted thereon. An aperture in the body member, proximate the apex of the collector, allows discharge of the fluid through a passage in the body member, past a pair of radiation detectors, thereafter returning into the well. A tracer ejector valve assembly is mounted proximate the apex of the funnel and the aperture therein for selectively injecting a quantity of radioactive tracer element into the fluid flow. The tracer element is detected by the pair of detectors with the signals provided therefrom used to determine flow characteristics of the fluids within the well.

Abstract: A device for providing both thermal protection and radiation shielding for components within a well logging instrument. A thermally insulative flash contains a mass of eutectic material which undergoes a change of state at a temperature which will provide an acceptable thermal environment for such components for extended time periods. The eutectic material has a density facilitating its use as a radiation shield and is distributed around the component so as to selectively impede the impinging of the component by radiation.

Abstract: A source of high energy neutrons and a detector responsive to the thermal neutron population decay rate are utilized in a well logging instrument. The instrument is positioned within a borehole and at least a portion of the fluids within the borehole are irradiated with high energy neutrons. The thermal neutrons emanating from the irradiated fluids are detected and measured. The thermal neutron counts are converted into a time base measurement which is further converted into a measurement of the thermal neutron capture cross-section for the irradiated fluids.

Abstract: Method and apparatus are provided for measuring acoustic signals having amplitudes of widely varying magnitude during one traversal of the borehole corresponding to indications of cement bonding along a casing as well as acoustic travel time through an increment of the formation. Variable attenuators are provided associated with acoustic receivers disposed within the logging sonde wherein attenuation may be automatically adjusted as a function of acoustic transmitter-receiver trigger pulses transmitted downhole, depending upon whether a cement bond or other log of acoustic signal information having a substantially different magnitude is desired.

Abstract: A method for determining the water saturation of subsurface earth formations substantially independent of lithology utilizing electromagnetic energy propagation measurements. The subsurface formations are first logged to obtain base log measurements of the dielectric permittivity of the formations as derived from electromagnetic energy propagation time values. The formations are then injected with a sufficient amount of oil miscible solution containing a surface active agent to displace substantially all the residual fluids from the formations for a radial distance at least equal to the radial zone of investigation. The formations are then injected with a sufficient amount of water to render the zone of investigation substantially 100 percent water saturated. The formations are logged a second time to obtain measurements of the dielectric permittivity of the saturated formations.

Abstract: The volume of clay within earth formations is determined throughout the vertical extent of a borehole using measurements of the natural gamma rays emitted from these formations comprised substantially entirely of clay. The clay volume determination is used for evaluating the volume of potassium oxide present in the formations. The percent of expandable layers present within the formations is determined, as a direct indicator of potential clay swelling difficulties and thus sensitivity to formation damage sensitivity, based on an extropolated and normalized potassium oxide volume. The percent expandable layers determination is used for determining the cation exchange capacity of the formations.

Abstract: Method and apparatus for completing sursurface formations traversed by a borehole. A perforating gun and a firing head assembly are run into the borehole on the end of a tubing string. A percussion firing assembly subsequently is lowered through the tubing string and latches into the firing head assembly. To initiate the firing system an impact member is dropped through the tubing string. Should ignition fail to occur the percussion firing assembly can be detached and removed from the borehole. Additional percussion firing assemblies can be lowered into engagement with and removed from the firing head assembly as desired. Further, an electrical firing assembly can be lowered through the tubing string into engagement with the firing head assembly and an electrical control signal used to detonate the perforating gun.

Abstract: An electrical signal representative of the detection of a mechanical coupling within a string of tubular goods is coupled into one input of each of a pair of parallel configured comparators. When the input signal level exceeds the value of complimentary reference levels the respective comparator generates an output signal. The composite output signal from the comparators is converted to a d.c. level which is compared to a fixed reference potential related to the duty cycle of a typical input signal. The comparator output signal is integrated and the peak value of which is stored by a peak detector. In the preferred embodiment the peak value is converted into digital form by an analog-to-digital converter.

Abstract: A computer-based well logging system is disclosed, for acquiring nuclear well log data, including gamma ray energy spectrum and neutron population decay rate data, and providing a real-time preentation of the data on an operator's display based on a traversal by a downhole instrument of a prescribed borehole depth interval.For acquiring energy spectrum data, the system has a multichannel analyzer including a pulse height analyzer and a memory. After a spectral gamma ray pulse signal coming from a downhole instrument over a logging cable is amplified and conditioned, the pulse height analyzer converts the pulse height into a digital code by peak detection, sample-and-hold action, and analog-to-digital conversion. The digital code defines the address of a memory location, or channel, corresponding to a particular gamma ray energy and having a count value to be incremented. After a period of time, the memory channels contain a spectrum of counts per incremental energy band.

Abstract: An improved well logging system and method is provided for deriving and visibly displaying a recordable representation of a comprehensive lithological profile of the earth materials traversed by a borehole. In a particular form of the invention, all logging measurements are derived in digital form and on the same depth-dependent bases, such that measurements taken during one trip through the borehole may be combined or processed with other logging measurements taken during a different trip through the same borehole of interest, such that all of the measurements may then be processed at one time to derive the various lithological indications sought to be provided.An improved monitoring system and technique is further provided, such that those logging measurements and lithological relationships of interest may also be correlatively displayed on a real-time basis with respect to at least some of the logging measurements from which they are derived.

Abstract: In a neutron induced gamma ray well logging instrument, a neutron generator is pulsed at a predetermined clock frequency. Each neutron burst produces inelastically scattered gamma rays and thermal neutron capture gamma rays. Inelastically scattered gamma rays are detected during a time interval coinciding with the neutron source pulsing for a first plurality of neutron bursts. Capture gamma rays are detected during a time interval subsequent to the cessation of the neutron burst for a second plurality of neutron bursts. A detection pulse is transmitted to processing circuitry during each of the detection intervals. Sync pulses generated in the well logging instrument are transmitted to the processing circuitry along with the detection pulses. The sync pulses are used to route the pulse occurring during the inelastic detection interval to one section of a multi-channel analyzer. Similarly, the pulse occurring in the capture interval is routed into another section of the multi-channel analyzer.