Abstract: A bullet perforating apparatus for perforating subsurface formations traversed by a borehole. The bullet perforating apparatus comprises a gun body with a plurality of bullet perforating gun assemblies. The individual gun assemblies further comprise a gun barrel, a cartridge tube with propellant, means for igniting propellant, a projectile, and a seal at the well bore end of the barrel. The barrel further comprises an outer member and a replaceable wear member securely retained within the outer member.

Abstract: Methods for estimating shear wave travel time in formations of mixed lithology employing the compressional wave travel time in conjunction with other logging derived information. A shear/compressional wave travel time ratio is established for a sand formation as a function of the porosity of the formation. A shear/compressional wave travel time ratio is established for a shale formation as a function of bulk shale density as derived from the bulk density of the formation. A shale factor is used to compensate the two ratios to the mixed lithology of the measured formation providing a shear/compressional wave travel time ratio for the measured formation. Shear wave travel time is determined using the formation travel time ratio and a compressional wave travel time measurement.

Abstract: An improved method and apparatus for displaying visual indications of subsurface-derived earth measurements. Digital logging measurements are delivered to video circuits for graphic display. The video circuitry includes a cathode ray tube and digital processing circuitry whereby an image is continually scrolled along with depth reference lines in correlation with movement of the sonde through the borehole. A moving visible representation of a preselected portion of the measurement may thus be continuously observed as it is obtained, moving relative to the display to simulate sonde movement within the borehole. A digital memory technique reduces the number of digital co-ordinates required to be stored and time required for visual data and reference line generation and scrolling wherein digital representations of starting co-ordinates are sequentially incremented and displays made in functional response thereto.

Abstract: Method and apparatus for firing perforating apparatus in a borehole. A mechanically operated firing assembly is run into the borehole on the end of a cable and latched onto a perforating apparatus. Tension is pulled on the cable. At a predetermined tension force a firing rod is automatically released and as a result of force exerted by a compression spring driven into impactment with a percussion firing head to thereby detonate the perforating apparatus. Additionally, the firing assembly can be reset by application of downward force thereto.

Abstract: Gamma rays from a subsurface earth formation are detected, and measurement of their respective energy levels transmitted to the surface where the resultant spectral data is stored in a plurality of narrow energy windows. Functional relationships relating photoelectric cross-section, density, and soft-to-hard ratio are developed from a formation model. These relationships are utilized with the stored spectral data in a perturbative process whereby effect of photoelectric cross-section on density is reduced and improved accuracy in density determination effected. Additionally, density is factored into photoelectric cross-section determination, compensating for effects of density on the soft-to-hard ratio. Availability of the entire spectrum permits improved resolution of the windows, monitor peaks, and detectors, and permits compensation for detector resolution in the observed spectrum.

Abstract: A shaped charge perforating unit includes a housing having a cavity formed therein. An explosive charge of high explosive material is retained within the cavity by a liner of non-explosive material. The explosive charge consists of quantities of two explosive materials having different detonation rates.

Abstract: The volume of clay within clay-bearing formations is determined throughout the formations. This volume of clay is then functionally related to measurements indicative of the formations. Utilizing measured formation characteristics representative of different clay types, such as potassium content or bound water content, the formation porosity measurements are extrapolated to indicate the porosity log measurements which would be yielded if the logging devices were responsive only to the clay within the formations. In addition the cation exchange capacity and the percent of expandable clay layers for the shale zones are determined. These extrapolated measurements are then related to known or determinable formation characteristics to determine additional formation properties such as porosity, permeability, and fluid saturation characteristics.

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: Method and apparatus for evaluating subsurface formations utilizing natural gamma radiation spectral measurements. The total counts measurement is processed to derive measurements relating to the concentrations of potassium-40, uranium and thorium. A relative concentration factor of uranium to the energy spectra is derived and the total counts measurement is compensated by the uranium factor to remove the effects of uranium.

Abstract: In a neutron induced gamma ray well logging instrument, a neutron generator is pulsed at a preselected clock frequency. Each neutron burst produces inelastic scattering gamma rays and capture gamma rays. Inelastic scattering gamma rays are detected using a bismuth germanate scintillator during a first time interval coinciding with the neutron source being on. Capture gamma rays are detected by bismuth germanate scintillator during a second interval subsequent to the termination of each neutron burst. The detected pulses are converted into electrical pulses by a photomultiplier. The electrical pulses are coupled into processing circuitry. The use of address decoders, subtractors and ratio circuits enables measurements of the characteristic full-energy photopeaks of selected elements within the formations.

Abstract: The volume of clay within clay-bearing formations is determined throughout the formations. This volume of clay is then functionally related to measurements indicative of formation porosity, such as density and neutron well logs of the formations. Utilizing measured formation characteristics representative of different clay types, such as potassium content or bound water content, the formation porosity measurements are extrapolated to indicate the porosity log measurements which would be yielded if the logging devices were responsive only to the clay within the formations. These extrapolated measurements are then related to known or determinable formation characteristics to determine additional formation properties such as porosity, permeability, and fluid saturation characteristics.

Abstract: Method for generating a composite logging data base from two separate historical data bases in a form suitable for further on-site computerized analysis and processing. A generalized system is provided for automatically producing, as a function of a plurality of elected options, an output which is either a merger of logging curves from the two data bases, a replacement of one or more logging curves or portions thereof from one data base with those of a correlative curve or curves from the second data base, or a splice of one or more logging curves from one data base derived over one borehole increment with a curve or curves from the second data base derived over a different borehole increment, with further provision for automated renaming and reordering of curves as they appear in the output as well as compatibility checks between the two data bases thus being combined in terms of logging parameters and borehole increments as a function of the elected option.

Abstract: An improved small diameter, high density shaped charge perforating apparatus is provided. The perforating apparatus includes an elongated carrier member having a plurality of shaped charge receiving stations spirally located therealong. The anterior and dorsal sections of the shaped charges extend outside the outer diameter of the carrier member and a length of helically wound detonator cord passes through an axial aperture in the dorsal section to retain the shaped charges in the carrier member. An alignment member is connected to one end of the carrier member to prevent rotational movement of the carrier member within the gun body and aligns the axis of perforation for each shaped charge with spotfaces on recesses in the periphery of the gun body.

Abstract: A subsurface geophysical parameter measurement is converted downhole to a first pulse train whose instantaneous frequency is a function of the parameter value. In response to a first control signal, a first counter begins a first count of pulses from the first pulse train, and a second counter begins a count of second pulses from a downhole reference oscillator. The first and second counts are terminated in response to a second control signal and the first and second counters are interrogated. A ratio is then developed between the first and second counts which is functionally related to the value of the parameter.

Abstract: An elongated body member adapted to traverse a well contains a chamber for holding a quantity of a tracer element to be injected into the well. A radially extendable arm is pivotally attached to the body member and is adapted to be extended and retracted by a first drive system within the body member. A nozzle is coupled to the arm with a path of fluid communication provided between the chamber and the nozzle such that a second drive system within the body member may cause the tracer element to traverse such path and be released into the well fluid flow column from a location adjacent to the body member and preferably to be released in a generally longitudinal direction relative to the well. One or more detectors within the body member suitable for detecting the tracer element are utilized to determine the locations and/or flow velocity of the tracer element and therefore of the well fluid.

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: 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: 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: 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: 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.