Abstract: A borehole televiewer scans forwardly to produce images of objects longitudinally ahead of the televiewer. The transducer is orbited around the bottom of the televiewer housing and simultaneously moves radially inwardly and outwardly thereacross to image an entire solid angle across a transverse section of the borehole ahead of the televiewer.

Abstract: The present invention is directed to an apparatus useful in downhole logging tools used in the oil and gas industry. The present invention is particularly directed to an acoustic logging tool including improved, articulated transducer pad assemblies for providing improved transducer contact with the wall of a borehole or the inside wall of casing cemented in the borehole. The apparatus of the present invention provides a plurality of articulated transducer pad assemblies disposed about the circumference of an acoustic logging tool in a plurality of separately movable and adjustable groups. These assemblies each include a plurality of articulated joints permitting limited independent movement of each assembly. The assemblies are spring biased at each end into a deployed configuration to maintain good contact with the wall of the borehole or casing. A drive motor overcomes the biasing springs to retract the assemblies to provide a compact tool for tripping to the location of interest within the borehole.

Abstract: In accordance with principles of the present invention methods and apparatus are provided for evaluating the quality of the cement bond in cased boreholes. Acoustic energy is used to excite the borehole-casing-annulus-formation system and the quality of the cement bond is determined by examining the ratios of the signals received by two longitudinally spaced apart receivers supported on a sonde. The acoustic energy is generated by two transmitters symmetrically disposed above and below the receivers along the sonde. The spacings between the receivers themselves and between the receivers and the transmitters are selected so as to enhance the correlation between the ratios of the received signals and the quality of the cement bond log. An additional receiver, supported on the sonde at a small distance from one of the transmitters, is employed to determine the quality of the cement bond in hard formations.

Abstract: A method of identifying the presence, type and extent of internal casing wear and distinguish worn casing from various types of unworn casing. Two inspection instruments are tied together in the combination traverses a section of casing where information on internal wear is desired. The first inspection instrument generates two signals related to the minimum and maximum wall thickness present at each location within the casing section. The second inspection instrument generates a signal related to the degree of phase shift at each location of the casing section.

Abstract: A modified acoustic logging tool to evaluate the condition of a gravel pack is disclosed. Said tool is placed in the wellbore near the gravel pack. An initial log is obtained via said tool at the conclusion of the initial gravel pack treatment. Information gained from the log is indicative of gravel fill and quality. Subsequent logging measurements are indicative of changes in said pack and indicative of remedial treatments.

Abstract: A method and apparatus for acoustically investigating a casing in a borehole are described. An electronically scannable acoustic transducer is formed on a planar circular surface and is oriented on a tool so as to direct circumferentially scannable beams of acoustic energy initially in an axial direction and subsequently in a radial direction onto the casing. Acoustic reflections from casing wall segments are detected and the frequencies of the casing reverberations present in the reflections are measured. One frequency measuring technique employs a reiterative technique whereby a previously measured frequency of a reflection attributable to one wall segment is used to generate a subsequent pulsed acoustic beam at the same wall segment. The number of reiterations may vary and is selected to accurately determine the thickness resonance of the casing.

Abstract: A method of determining the presence of channels in the cement behind a well casing utilizing the temperature profiles of the well. In a first embodiment rate coefficients indicative of the rate of temperature change along a zone of investigation are calculated from the geothermal gradient, flowing temperature profile and at least one shut-in temperature profile. These rate coefficients are plotted versus depth, with inconsistencies in the valves of the rate coefficients being indicative of the presence of channels. In a second embodiment rate coefficients are calculated over a well bonded zone of the well casing and utilized to predict shut-in temperatures along the zone of investigation. Differences in the predicted and actual shut-in temperatures is further indicative of the presence of channels.

Abstract: A pressurized liquid column is fed down the tubing string of a well and out of the well to the earthen formation at the bottom of the string. Mounted within the tubing string is an elastic rod string and the tubing plus the rod may comprise an elastic column. A vibration generator which may comprise an orbiting mass oscillator is mounted on the top of the rod string or both rod and tubing, the oscillator being operated at a sonic frequency which will effect resonant standing wave vibration of the rod string. A plurality of sonic impeller elements are fixedly mounted on the rod string at spaced intervals therealong, the spacing between such impeller elements being les than 1/10th of the wave length of the standing waves. The impeller elements are designed and oriented so as to effect downward pumping action of the liquid column in response to the sonic energy.

Abstract: The potential for failure of a formation is predicated by using standard logging apparatus and techniques to monitor the change in a formation characteristic over an extended time period. Changes in this characteristic are attributed to absorption of fluid by the formation which could lead to a possible breakdown of the structural integrity of the formation.

Abstract: A method and apparatus are disclosed for acoustically investigating a borehole casing cement bond. A sonde is provided which is adapted to be lowered into a borehole and which includes a plurality of acoustic transducers arranged in a helical array around the sonde. A short duration acoustic pulse is directed at the borehole casing from each transducer and the reflection signal generated thereby is coupled to an autoregressive adaptive filter which automatically adjusts its filter coefficients to achieve a desired output signal. The adjusted filter coefficients are then utilized to determine the frequency and decay rate of the reflection signal and the frequency and decay rate of the reflection signal may be utilized to determine selected characteristics of the casing and the cement bond. In a preferred embodiment of the present invention, an additional transducer is mounted a selected distance from a fixed reflector to obtain standard transmission characteristics.

Abstract: A method for evaluating the quality of the cement surrounding a borehole casing is provided. The method generally comprises obtaining signals which were recorded by a CET tool known in the art, and processing the signals by: dividing each signal into particularly defined time windows; determining absolute magnitudes for each signal which are functions of the energy of the signal in the respective windows; determining normalized magnitudes for each signal from the absolute magnitudes and normalization parameters; and evaluating the quality of cementation as a function of the fact that the normalized magnitudes for each signal obey a predetermined law, and as a function of the relationship between each normalized magnitude and a pair of threshold values respectively associated therewith.According to another aspect of the invention, information obtained from a CBL tool known in the art is compared to the information gained from the CET tool.

Abstract: Method and apparatus for measuring formation compressional and shear wave velocities characterized by a downhole tool having an attenuation chamber between a transmitter and a receiver and a plurality of receivers spaced from the transducer so as to discriminate through the amplitude of the reflected compressional wave the critical angles for the respective formation compressional and shear wave velocities, thereby determining the formation compressional and shear wave velocities. Also disclosed are preferred embodiments in which the plurality of connectors connected between the receivers are also connected with a recorder for recording gated time interval signals. A discriminator and gate are provided for discriminating the largest amplitude of received acoustic energy signals received during the gating period.

Abstract: A 60 to 100% coverage of downhole casing condition is obtainable by the improved system comprising, a sufficient number of piezoelectric transducers 1/4 inch in diameter about a probe head, preferably, 40 or more and usually 60-120 piezoelectric transducers located in a housing coupled to an electronic package also in a suitable downhole housing. The system reports all exceptional data and certain selected regular or non-exceptional data, displaying it topside and establishing a permanent record using existing wire line facilities.

Abstract: A logging method and apparatus are provided for the acoustic inspection of a borehole fitted with a casing wherein obtained measurements which are representative respectively of one or more data items relating to the casing and to the material which surrounds it are corrected for the effects of the environment.

Abstract: The present invention relates to an apparatus and method for calipering a borehole using acoustic measurements within the borehole. These acoustic measurements are useful for measuring the reflectivity of the side walls of a borehole and for calipering a borehole in a wireline or measurement while drilling configuration. The apparatus comprises at least one acoustic transceiver disposed on a calipering tool, together with a second acoustic receiver disposed longitudinally a selected distance from the first receiver. Further, a second acoustic transceiver is disposed on the caliper tool azimuthally from the first transceiver. Measurement of the travel times of acoustic pulses reflected from the borehole walls by the transceivers and receivers of this device, together with other known data, permits an accurate caliper of the borehole to be produced.

Abstract: The inventive multipole acoustic wave logging method includes the steps of introducing a 2.sup.n -pole acoustic wave into a virgin earth formation surrounding a borehole but separated from the borehole by an invaded zone, where n is an integer greater than zero, and detecting the refracted arrival of the 2.sup.n -pole acoustic wave. The inventive apparatus includes means, separated from the borehole wall during operation, for generating a 2.sup.n -pole acoustic wave that will propagate through the borehole fluid and thereafter into the virgin earth formation. If the 2.sup.n -pole acoustic wave is a compressional wave, the compressional wave velocity of the virgin formation is determined from repeated measurements, at successively increased longitudinal spacings between the points of generation and detection of the 2.sup.n -pole wave, of the time interval between detections of the refracted arrival of the 2.sup.n -pole acoustic wave by the two detectors. If the 2.sup.

Abstract: Apparatus for generation of shear or compressional type vibrations within a borehole wherein oppositely oriented first and second acoustic energy sources are energized to produce output tube waves which, in turn, are equally deflected to propagate energy toward opposite sides of the borehole. Energization of the sources in-phase effects output of compressional wave energy and energization of sources 180.degree. out of phase results in shear wave generation.

Abstract: A string of pipe is provided with intermittent coatings of grit-like materials bonded to the pipe to provide a rough surface for adhesion of cement in a cementing operation. Between the intermittent coatings are intermittent bare portions of pipe thereby to permit the use of a cement bonding tool. The spacings of the coatings is functionally related to the transmitter/receiver spacing for a cement bonding tool.

Abstract: The apparatus and method of the present invention pertain to visual presentation systems employing scan lines, wherein each scan line is divisible into sets of points respectively corresponding to locations at which well measurements are made. The resulting sets are shaded in accordance with the value of the respective measurements. Harsh transitions between adjacent sets are removed by having a parameter evaluated for each point of the scan line in accordance with (a) the spatial relationship of a subset of points which includes the point to adjacent sets of points; and (b) the well measurement made at the location to which the point corresponds. The parameter value is compared with a randomly or pseudo-randomly generated number, and the point is marked if the result of the comparison satisfies a preselected relationship. The parameter is evaluated and the comparison is made for all other points in the scan line.

Abstract: A method and apparatus of detecting fractures along the wall of a formation, such as a well formed by test-drilling, provides for the transmission of ultrasonic signals in a direction essentially perpendicular to the wall from a position spaced from the wall by a predetermined distance and the reception of the ultrasonic signals which may be reflected by the wall. The space of predetermined thickness between the transducer which generates the ultrasonic signals and the wall is filled with an intermediate material which does not form a distinct interface with the wall of the type which would be able to produce an appreciable parasitic reflection of the transmitted signals.

Abstract: A method and apparatus using a multiple transducer acoustic logging tool to detect fractures surrounding a borehole, particularly fractures that do not intersect the borehole wall. The transducers are actuated to produce broad band width pulses and signal enhancement techniques are used to determine fracture width, orientation and distance from the borehole wall.

Abstract: An acoustic borehole tool consists of two components: A first component containing power supplies, signal processing and control electronics and a sidewall locking mechanism. A second component includes a seismic sensor and a clamping device for pressing the sensor against the sidewall of a borehole. The weight of the second component is a small fraction of the weight of the first component so that the force exerted by the clamping device is less than a preselected limiting value and so that the clamping force/mass ratio may reach large value without danger of destroying the borehole.

Abstract: A method for finding the distance between a blowout well and a relief well. The method comprises measuring the acoustic noise in the relief well at two or more locations and then calculating the distance to the blowout well.

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: A borehole logging tool employs an energy transmitter and receiver for scanning a borehole with energy pulses. An orientation pulse is produced each time the tool rotates past a predetermined orientation position. The time period between orientation pulses is measured and divided into a plurality of discrete intervals. Sine and cosine functions are generated for the measured time period having a sine and cosine value corresponding to each of the discrete intervals. The sine and cosine functions are used to produce sweep functions for controlling the outward sweep of the electron beam of a PPI display device so as to produce a circular rotating pattern in which each revolution corresponds in time to a measured time between orientation pulses. The output of the receiver modulates the electron beam sweep to generate a visual display of the azimuthal scan of the borehole.

Abstract: Apparatus is provided to detect a discontinuity indicative of a hole in the bore wall of an axially extending tubular member. It comprises:(a) a carrier to be traveled axially lengthwise in the bore of the tubular member,(b) an acoustical wave transmitter located on the carrier to transmit acoustical waves for travel toward the bore wall and for reflection therefrom,(c) an acoustical wave detector at least partially located on the carrier to receive acoustical waves reflected from the bore wall and to detect the presence or absence of such reflected waves, and(d) a control for providing an indication of such discontinuity, and for controlling the transmission to the detector of the reflected acoustical waves, and characterized in that the detector is controllably exposed to reception of a sequential succession of reflected acoustical waves corresponding to a sequential succession of bore wall portions from which the waves are reflected.

Abstract: In an acoustic logging system for providing information regarding selected parameters of the wall of a borehole in the earth, and of the rock formation which is adjacent the borehole, in which a single transmit/receive transducer system (T/RTS) mounted on a rotating assembly probes the wall of the borehole in a circular scanning pattern as a function of depth, the improvement which includes at least a second T/RTS mounted on the rotating assembly in known geometrical relation to the first T/RTS, and means to process two or more analog electrical scan signals for transmission over one or more electrical transmission channels in a logging cable. In particular, methods and means are described for transmitting multiple scan signals whereby a higher speed of logging is possible without loss of detail of the logs and without modification of the mechanical system of the logging sonde.

Abstract: A measurement system detects a downhole drilling variable in relation to the rotational orientation of a drill string during drilling. The system includes a downhole reference signal generator and a downhole variable signal generator. The reference signal generator is coupled downhole to the drill string for generating a downhole reference (DR) signal indicative of the angular relationship between the angular orientation of a lower portion of the drill string about its axis and a directional reference, such as gravity or the earth's magnetic field. The downhole variable signal generator detects downhole parameters and generates a downhole variable (DV) signal representative of a downhole parameter of interest during drilling, such as the bending moment applied to the lower portion of the drill string.

Abstract: The length and width of fissures in a bore hole is determined by alternately flowing liquid into and out of the formation from an isolated zone of a bore hole, at different frequencies, and measuring the dynamic pressure of the flowing fluid. The length of fissures in the isolated zone is determined from frequency peaks at high pressure to flow ratios, and the thickness of the fissures is determined from variations of pressure-flow ratios with frequency by comparison with known data. Sonde apparatus for practicing the method is also disclosed.

Abstract: An apparatus for accurately determining the relative positioning of a well logging sonde or downhole tool in a bore hole is disclosed. The apparatus comprises an anchor for engaging the wall of the bore hole in fixed position and adapted to be carried into the bore hole on the downhole tool suspended on a logging wireline to a selected level, and a release mechanism controllable from the surface for releasing the anchor from the tool so that the tool can move independently of the anchor element. A sensing cable interconnects the anchor and the tool and is payed out from a reel carried by the tool as the tool separates from the anchor. Means actuated by the sensing cable are provided for transmitting electrical pulses up the wireline to the surface to indicate the relative distance between the anchor and tool.

Abstract: An improved well logging technique is provided for more accurately deriving acoustic measurements of sub-surface earth formations. Method and apparatus are described for converting an acoustic signature which can be generated on a depth dependent or time dependent basis, into digital format and subsequently employing special processing techniques to yield parameters such as velocity of the transmitted acoustic energy through earth formations and the amplitude of the received acoustic energy. Processing further allows for the generation of noise immunity signals functionally related to a measured signature parameter and for the generation of amplitude control signals. Additionally, a control signal is generated to optimize transmitter firing rate.

Abstract: An apparatus is described for acoustically investigating a casing in a borehole with a source of acoustic energy that is directed at the reflecting surface of an acoustic reflector in front of which is an acoustically transparent window. The inclination of the window relative to the reflecting surface is selected to deflect secondary transmissions and thus reduce window produced interferences. Several embodiments are described.

Abstract: The present invention provides a method and apparatus of differential noise logging. The apparatus includes a mandrel supporting at least two differentially connected acoustic transducers. The noise signals detected by the transducers are filtered, processed by RMS circuits and then subtracted one from another to effectively eliminate road noise. A telemetry system is utilized to send the signals uphole for recording. The differential logging method includes continuous movement of the differential noise logging tool to identify producing perforations, distinguish flow through perforations from flow being casing, and to identify sand jet entry into a cased well.

Abstract: A method of logging a wellbore to identify oil, gas and water zones in a hydrocarbon-bearing formation that is characterized by acoustic velocities which are maximum when saturated with oil, minimum when saturated with water and intermediate when saturated with gas. The formation is logged with a sonic logging system utilizing a frequency within the range of 0.1 to 10 KHz and logged with a lithologic logging system to account for variations in lithology on the sonic log. Thereafter the sonic log is compared with the known acoustic velocity characteristic of the hydrocarbon-bearing formation to identify the oil, gas and water zones therein.

Abstract: A measurement system detects a downhole drilling variable in relation to the rotational orientation of a drill string during drilling. The system includes a downhole reference signal generator and a downhole variable signal generator. The reference signal generator is coupled downhole to the drill string for generating a downhole reference (DR) signal indicative of the angular relationship between the drill string and a directional reference, such as gravity or the earth's magnetic field. The downhole variable signal generator detects downhole parameters and generates a downhole variable (DV) signal representative of a downhole parameter of interest during drilling. The DV signal and the DR signals are thereupon processed, either downhole or uphole depending in part on the telemetry system employed. The system is especially adapted for indicating the resultant lateral force applied to the drill string at the drill bit during drilling which is useful in projecting the probable drilling direction.

Abstract: A borehole investigating device takes measurements of a subsurface earth formation and provides signals forming sonic, formation density or similar logs of the borehole. Additionally, the investigating device measures the dip of seismic signal reflectors traversed by the borehole and provides corresponding dip signals. A seismic section which may or may not include the borehole is selected, and the log and dip signals are combined with signals defining the location of the seismic section with respect to the borehole, to thereby provide synthetic logs for each of a number of virtual boreholes which coincide with selected virtual and/or actual shotpoints of the seismic section. The synthetic log signals are then combined to form a truly two-dimensional synthetic seismogram for the selected seismic section. The synthetically derived signals may be corrected in accordance with a selected geological model of the formation.

Abstract: Methods and apparatuses for acoustically investigating a casing in a borehole to derive the quality of a cement bond behind the casing and casing thickness are described. The techniques employ an acoustic pulse source having a frequency spectrum selected to stimulate a selected radial segment of the casing into a thickness resonance. The selected frequency spectrum enhances the reverberations between the inner and outer walls of the casing which traps the thickness reverberations with significant amplitudes for a duration depending upon the amount of acoustic energy leaked into adjacent media. The acoustic pulse causes acoustic returns which are formed by the reflections from interfaces between media of different acoustic impedances and acoustic energy leaked into the bore of the casing from the acoustic thickness reverberations stimulated within the casing walls. The acoustic returns are detected to generate a reflection signal which is processed to determine casing thickness or to evaluate the cement bond.

Abstract: Acoustical logging apparatus is utilized to determine the need for consolidation treatment of an oil-bearing sand formation prior to production and preferably prior to the removal of the drill rig. The relative energy levels and/or the relative velocities of the compressional and shear waves are measured and the ratio of the compressional energy to shear energy and/or the ratio of compressional velocity to shear velocity is utilized to provide an indication of the need for sand consolidation treatment.

Abstract: An acoustic source and a spaced-apart acoustic receiver are moved through the casing of a well. Electrical signals indicative of the source signal and the receiver signal are applied uphole by way of a conductor to a time series analyzer and recorder. The time series analyzer provides power-spectral density functions and cross-spectral density functions of the source and receiver signals during reconnaissance logging operations. From these functions there is determined the ability of the casing-cement formation combination to transmit the source signal to the receiver and also the linear correlation of the source signal and receiver signal.

Abstract: An acoustical logging tool having a plurality of long, extendable, resilient arms, and means for remotely extending free ends of the arms into close proximity to the wall of a borehole. A cylindrical transducer is mounted on the free end of each arm, with some of the transducers being used as transmitters and the remainder as receivers. The signals from the receivers are separately recorded to provide a side-by-side comparison of the signals. The proper spacing of the transmitters and receivers will produce a complete circumferential acoustic log of the borehole that can be used to detect the presence of vertical fractures.