Abstract: An improved well logging technique is provided for more accurately deriving and correlating a plurality of measurements made during a single traversal of a logging instrument through subsurface formations. In one exemplary embodiment, methods and apparatus are provided for deriving a more accurate and precise measurement of depth at which real-time logging measurements are made, and in particular for correcting anomalies occurring in the depth indication from cable stretch, yo-yo of the sonde in the borehole and the like. The more accurate and precise depth measurement is then utilized for generating well logging measurements on a depth-dependent basis, deriving at least some of such measurements in digital form and alternately transmitting to the surface digital and analog representations of such measurements.

Abstract: A logging instrument is caused to traverse a cased earth borehole periodically emitting and receiving acoustic energies, such instrument generating an electrical signal containing one or more electrical alternations representative of the received acoustic energies, and such alternations having an amplitude generally functionally related to the attentuation of the acoustic energies as they traverse the casing within the borehole. A significant portion of these alternations is determined and digitized, and the individual digitized values therein summed together to yield a functional representation of the signal area of the alternations of a predetermined polarity within the significant portion. This signal area is then compared to the area which would be indicated if the casing were free of cement bonding, the comparison yielding an indication of the relative degree of bonding of cement to the casing within the borehole.

Abstract: Electronic circuitry to assist in obtaining measurements of subsurface formation parameters is mounted on an elongated chassis member removably disposed within a tubular housing. One or more restraining assemblies are disposed along the length of the chassis. Each restraining assembly includes a cam member biased into engagement with the inner periphery of the housing to provide a substantially rigid restraint of the chassis within the housing. An inertial latch is used to constrain the cam member within the chassis for insertion within the housing. A pair of fixed contact members are angularly disposed about the chassis in radially spaced apart relationship with the cam member to provide three contact points with the housing.

Abstract: Improved emulsifying agents for oil based drilling fluids, compared to imidazoline materials presently being used in oil based drilling fluids, that not only are excellent emulsifiers for oil based drilling fluids, but also are effective wetting agents and fluid loss control agents in invert (water-in-oil) systems, are obtained from imidazolines prepared by reacting long chain fatty acids with polyalkylene polyamines to form a 2-alkyl imidazoline, and then reacting the 2-alkyl imidazoline with an activated dicarboxylic acid to form the desired 2-alkyl imidazoline derivative.

Abstract: An improved method and apparatus for correlating logging curves particularly adapted to formation dip determination from wire line dip meter measurements. A plurality of data sets each having a corresponding formation resistivity logging curve associated therewith are generated from a borehole. An activity transform function is derived from each data set, the maxima above a predetermined noise level of which are utilized to determine a set of possible points on the respective logging curve for correlation with points on another such curve. The set of points is reduced in size according to criteria requiring all possible correlated point-pairs to be separated in depth by no more than a predetermined maximum search interval, and on respective curve segments having the same slope sign and shape, wherein the shape criterion is a function of the activity.

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: An improved transducer for generating and receiving acoustic energy. A transducer core is constructed by bonding together a plurality of concentric cylinders to provide a ferromagnetic core. A magnetic vector is established circumferentially about the core by passing a current through an electrical winding, wound torridially about the core. A pulsed current source connected across the core provides a high-magnitude, short-duration pulse output establishing current flow from one end to the other end of all of the concentric cylinders. Current flow within the magnetic field causes a force vector and magnetic vector creating a pressure wave.

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: A well perforating and completion apparatus includes a packer connectable to the lower end of a tubing string, a vent assembly connected below the packer for communication between the tubing string and the annulus, a well perforating gun assembly having a hydraulically actuatable detonator and a hydraulic actuating fluid flow path between the detonator and the earth surface. A releasable coupling is provided between the packer and the vent assembly to permit disconnecting and dropping of the vent assembly and perforating gun assembly from the tubing string after the perforation has been accomplished to leave an open ended tubing string in the well. The well perforation and completion method of this invention includes assemblying the tool string on the tubing string then running it into the well and positioned with the perforating gun and the packer at the desired location.

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: 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 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: The improved dwell and depth attachment includes an elongate housing that is attached to a drill motor and has an output shaft that is movable longitudinally and rotatably in the housing for rotating a drill bit. A drive spindle is connected with the output shaft and extends through the housing. An elongated sleeve encircles the spindle and has an end that is engageable with the work piece. An adjustable depth control located within the housing is connected for movement with the spindle. A first portion of the control includes a threaded interior and has ten circumferentially spaced, radially extending holes therein. The control also includes a second portion that has a threaded exterior mating with the first portion and has ten slots equally spaced about the exterior. The threads are selected to be loose fitting so that the portions of the control can "float" relative to each other.