Abstract: A borehole televiewer apparatus includes a housing section having a cavity for the disposition of an acoustic signal transmitting and receiving transducer. An elongated threaded rod is disposed in the cavity and held stationary relative to the housing and supports a nut, a slipring assembly, the transducer and a drive motor assembly for axially translating the transducer and rotating the transducer while precluding rotation of the motor and a support plate therefor relative to the rod. The support plate is keyed to the rod by an elongated key and keyway configuration to prevent rotation of the motor and the support plate while permitting axial translation of the motor and support plate along the rod.

Abstract: A method for monitoring the relative goodness of a cement bond to a borehole casing by observing the relative change in amplitude of a converted-compressional wave as a function of depth in the borehole.

Abstract: The present invention is directed to an apparatus and method for obtaining azimuthally dependent measurements for evaluating the casing cement bond quality and, more particularly, for detecting and specifically locating channels or fissures between the casing and cement. The quality of the bond behind one or more arcs of known location on the casing is determinable by the present invention. The apparatus and method of the present invention employ a plurality of sonic transducers disposed in near contact with the casing in defined segmented locations about or around the exterior surface of a downhole tool. The transducers are arranged in a plurality of arrays, each array comprising four transducers, two transmitting and two receiving transducers, disposed along a single arc about or around the exterior of the tool.

Abstract: Data received from a sonde in a borehole is enhanced by first measuring the relative travel time of a signal transmitted from the sonde and reflected from an area in the wall of a borehole. This measurement is repeated for a plurality of angles in a horizontal plane. From this plurality of travel times a best fit ellipse or circle is calculated and the travel times are correlated with the best fit ellipse or circle to provide corrected travel times and to determine the eccentricity of the sonde in the borehole. The corrected travel times are displayed as images to indicate the detailed shape properties of the borehole.

Abstract: The growth of a hydraulic fracture increases the period of free oscillations in the well connected to the fracture. Simultaneously, the decay rate of free oscillations decreases. The properties of forced oscillations in a well also change during fracture growth. All of these effects result from the changing impedance of the hydraulic fracture that intersects the well. Hydraulic fracture impedance can be defined in terms of the hydraulic resistance and the hydraulic capacitance of a fracture. Fracture impedance can be determined directly by measuring the ratio of down hole pressure and flow oscillation or indirectly from well head impedance measurements using impedance transfere functions. Well head pressure measurements can also be used to evaluate fracture impedance by comparing them to pressure oscillations computed with hydraulic models that include fractures with different impedances.

Abstract: An apparatus and method of use thereof are disclosed herein for determining cement conditions adjacent a casing set within a wellbore. At least one acoustic transmitting and receiving transducer and at least one acoustic receiving transducer are positioned into contact with the interior surface of the casing. At least one pulse of acoustic energy is transmitted into the media surrounding the wellbore from the at least one acoustic transmitting and receiving transducer. Electrical signals are generated in response to acoustic energy received by both transducers from the surrounding media. Representations of the generated electrical signals are recorded as a function of the depth within the wellbore and are indicative of the cement conditions, including the casing-cement bond, the cement-formation bond, cement thickness, and the acoustic velocity associated with the cement.

Abstract: An apparatus and method of use thereof are disclosed herein for determining cement conditions adjacent a casing set within a wellbore. At least one acoustic transmitting and receiving transducer and at least one acoustic receiving transducer are positioned into contact with the interior surface of the casing. At least one pulse of acoustic energy is transmitted into the media surrounding the wellbore from the at least one acoustic transmitting and receiving transducer. Electrical signals are generated in response to acoustic energy received by both transducers from the surrounding media. Representations of the generated electrical signals are recorded as a function of the depth within the wellbore and are indicative of the cement conditions, including the casing-cement bond, the cement-formation bond, cement thickness, and the acoustic velocity associated with the cement.

Abstract: Disclosed herein are methods for canceling acoustic reverberations caused when acoustic energy impinges a medium. In one method, a series of positive pulses of acoustic energy are transmitted and the amplitudes of the resulting acoustic reverberations are measured. Negative pulses of acoustic energy are then transmitted having amplitudes equal to the immediately preceding received acoustic reverberation and at a time later than the positive pulses so that the acoustic reverberations are driven to a null.

Abstract: Using waveforms or travel time acquired by multitransmitter and/or borehole sonic tools, acoustic velocity (or slowness) is computed for compressional, shear, and Stoneley waves using direct phase determination (DPD), the slowness time coherence (STC) method, and multiple shot processing (MSP). There is a nonzero difference between transmitter and receiver delta-t's (slownesses) when the sonic tool is in the vicinity of a borehole feature, such as a fracture or a borehole enlargement. The amount of the difference, T/R delta-t, for compressional, shear and Stoneley waves depends on the size and nature of the fracture(s). It is possible to determine the height, width, and dip angle of the fracture when the T/R delta-t's are used in conjunction with other model data. It is also possible to distinguish between borehole enlargements and fractures with the method of this invention.

Abstract: Apparatus for positioning a detector at a plurality of depth locations within a large diameter borehole includes an elongated body member having a pair of diametrically opposed hydraulic pad displacement members mounted thereon. A pad mounting member is pivotally attached to each pad displacement member and a pair of borehole wall contacting members are pivotally attached to each pad mounting member. A signal detector is mounted behind one or more of the pad members. At each test depth a hydraulic power system deploys the pad displacement members from the body member to an extended position and extends the wall engaging pad members into contact with the borehole wall.

Abstract: In connection with a borehole televiewer system (10), the delta time (51) between low threshold (54) crossing (T.sub.1) and signal peak arrival (T.sub.2) provides a measure of mudcake (43) thickness.

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: A method and apparatus for determination of earth formation permeability in situ. A logging sonde supported in a borehole derives attenuation data from at least two ultrasonic energy transmission paths which have a common alignment but differing length, the attenuation data can then be used to determine an empirical X parameter that is directly related to formation permeability.

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 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: 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: An ultrasonic borehole televiewer is modified to provide a vertical array of receiving transducers arranged above and below a conventional transmit/receive transducer. The variation in amplitude of reflected energy detected across this array for each firing of the televiewer is a measure of the extent to which scattered energy is present in addition to specular reflections. This in turn is an index of the relative smoothness or roughness of the borehole surface on a scale comparable to or smaller than the wavelength of the incident energy.

Abstract: Dip measurements and investigation of geological formations traversed by a deviated borehole is carried out by means of an apparatus comprising a measuring sonde and a cartridge connected to a cable. The sonde carries four measuring pads regularly distributed by means of articulated arms which keep the pads parallel to the axis of the sonde. The opposite arms are forced to stay symmetrical in relation to the sonde.The sonde is connected to the cartridge so that its axis can depart angularly from the axis of the cartridge, enabling the latter to rest on the borehole wall. The pads have a length smaller than twice the transverse dimension D of the sonde.

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 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: The present invention relates to the acquisition of seismic signals at different levels in a borehole, in response to the generation of seismic waves by a source placed on the surface or in the vicinity of the surface. The acquisition is carried out by means of a sonde suspended in the borehole from a cable and equipped with an anchoring pad. At each acquisition level, the pad is anchored in the borehole wall to couple the sonde to the formation, and then the pad is released from the wall once the acquisition is over. The signals acquired are then sent to the surface by means of the cable. The force with which the pad is anchored in the wall is controlled by means of a feedback arrangement which includes a sensor arranged in the pad itself. During the sonde movements from one level to another, the pad is kept in contact with the wall.

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: The present invention relates to the acquisition of seismic signals at different levels in a borehole, in response to the generation of seismic waves by a source placed on the surface or in the vicinity of the surface. The acquisition is carried out by means of a sonde suspended in the borehole from a cable and equipped with an anchoring pad. At each acquisition level, the pad is anchored in the borehole wall to couple the sonde to the formation, and then the pad is released from the wall once the acquisition is over. The signals acquired are then sent to the surface by means of the cable. The force with which the pad is anchored in the wall is controlled by means of a feedback arrangement which includes a sensor arranged in the pad itself. During the sonde movements from one level to another, the pad is kept in contact with the wall.

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: 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: 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 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 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: 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: 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: Bursts of signals at different frequencies are induced into substructure, adjacent a borehole. The return signals from each burst of signals are normalized to compensate for the attenuation, experienced by more distant return signals. The peak amplitudes of return signals, above a selected level, are cut off, and an average signal is produced from the normalized amplitude-limited return signals of each burst. The averaged signals of the return signals of all the signal bursts at the different frequencies are processed, to provide a combined signal, whose amplitude is related to the microfracture density of the substructure adjacent the borehole.

Abstract: A pair of acoustic detectors are moved through a well to detect sound at various levels within the well. Electrical signals indicative of the detected sound are applied from the acoustic detectors by way of a conductor cable to uphole recording equipment including an amplifier, spectrum analyzer, crosscorrelator, and recorder. The spectrum analyzer provides frequency spectrums of the amplified signals from the acoustic detectors. The crosscorrelator provides an indication of the time differential between the traveltimes of acoustic noise to the acoustic detectors for use in the location of flow leaks through or behind the well casing.

Abstract: An acoustic detector is moved through a well to detect sound at various levels within the well. An electrical signal indicative of the detected sound is applied from the acoustic detector by way of a conductor cable to uphole recording equipment including an amplifier, spectrum analyzer, and recorder. The spectrum analyzer provides a frequency spectrum of the amplified signal from the acoustic detector. This frequency spectrum is recorded for use in the identification of flow leaks through or behind the casing of the well in accordance with predetermined spectrum analysis characteristics of single-phase gas and single-phase liquid leaks.

Abstract: An acoustical logging apparatus which has a means for interfering with those unwanted signals which inherently travel in the mud between the transmitter and the closest receiver of said apparatus during a logging operation. The signal interference means comprises a rotating sleeve having signal attenuation elements mounted thereon which are adapted to extend to the wall of the borehole to act as a centralizer when the apparatus is in the borehole. These elements are vertically stacked in an overlapped relationship so as to present an obstructed path through the mud for said signals but so as to offer only nominal resistance to displacement of mud as the apparatus is moved therethrough.

Abstract: Method for determining the shape of an underground cavity and the location of the interface between two media contained therein by making use of a sonic sonde comprising performing, for each position of the sonde, a series of measurements of the time interval between the transmission of an ultrasonic wave from the sonde and the reception of the corresponding echo after reflection on the wall of the cavity, the selection from said measurements of one of those indicating substantially identical time intervals so as to eliminate the false echos and the determination of the average value of the propagation time of said selected echo for each different location of the sonde and for each direction of the transmitted waves.

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.