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: 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: 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 utilize in combination the electrical scan signals from the at least two scanning T/RTS.

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: In accordance with illustrative embodiments of the present invention, methods for processing well logging data comprises deriving measurements of a plurality of earth formations parameters and combining these measurements in a new manner to enable interpretation of shales and shaly sand type formations. More particularly, measurements of a plurality of the hydrogen index, bulk density, radially deep and shallow resistivity, spontaneous potential, acoustic travel time and natural formation radioactivity content are made and combined in a manner to produce data useful in evaluating shales and shaly sand type formations.

Abstract: The amplifier has a fluid active medium and contained in housing (1). The medium is excited by electric discharge in a resistance (4) constituted by a conductive layer deposited on an insulating support.Application to iodine lasers.

Abstract: An apparatus for monitoring the testing of a subterranean well by acquiring data from the well includes means for monitoring transducers positioned downhole, at the wellhead, at a separator or at other locations to obtain the values for a predetermined set of operating characteristics. The apparatus includes a microcomputer for calculating additional characteristics utilizing one or more of the transducer values and a visual display for onsite viewing of the values for the monitored and calculated characteristics. The apparatus further includes a printer and a tape recorder. The microcomputer controls the recording intervals of the printer and the tape recorder for recording the monitored and calculated values of the characteristics on a continuous basis. The values of the characteristics represent current production information for the well. The apparatus also includes means for monitoring the transducer power supply voltage and the microcomputer power supply voltage.

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 system and method for processing and displaying well-logging data provides direct indications of various lithological characteristics in conjunction with symbolic representatives of formation lithologies. Preselected programming of a two-dimensional symbol matrix into a memory device provides symbol flexibility. Geometric symbol matrices corresponding to different formation characteristics are digitally stored. When a preselected relationship occurs between lithological characteristics, the particular preselected matrix corresponding to the relationship is repetitively retrieved and displayed between the lithological characteristics curves. Because a relatively small digital matrix pattern may be used and repeated, only a small amount of storage is required for each symbol.

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 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: Techniques for a broad band high frequency acoustic investigation of a subsurface formation around a borehole are described utilizing a range of acoustic frequencies selected to produce detectable acoustic backscatter from grains within the subsurface formation. The acoustic backscatter is detected and a spectrum thereof is produced and averaged over adjacent subsurface formation regions. A subsurface formation parameter such as the frequency dependency of the attenuation of the backscatter is determined from an analysis of the spectrum to provide an indication of the granularity property of the subsurface formation. Use of a broad range of frequencies enables a determination of the subsurface formation parameter over a large range of grain sizes. In another technique the spectrum of the detected backscatter is modified to remove the effect of the frequency response of the system with which the investigation is made.

Abstract: Electroacoustical transmitting or receiving transducer comprising a flat disc piezoelectric transducer element aligned with a conical reflector. The disc transducer element is positioned to transmit acoustic energy in a direction parallel with a borehole axis and this energy is reflected by the conical reflector so that it impinges upon a borehole wall near the critical angle to provide maximum propagation of energy in the rock in one direction parallel to the borehole. The same transducer arrangement also functions as an efficient directional receiver of acoustic energy.

Abstract: A surveying instrument for investigating the character of an underground cavity penetrated by a borehole, includes an elongated instrument housing and a lower section containing means to generate and receive energy, such as a surveying transceiver. The lower section is pivotally and rotatably movable about the lower end of the housing enabling the entire surface of the cavity to be surveyed.

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.