Mobil Oil Corporation

Joseph Zemanek, Jr

Charles L Dennis

Khalid A Alhilali

Frank A Angona

James A Clishem

An acoustic transmitter is employed in a borehole logging tool for generating low frequency acoustic energy waves. A tube of piezoelectric material is sealed at both ends and filled with liquid. A pliable boot surrounds such piezoelectric tube. At least one passageway communicates the inside of the piezoelectric tube with the inner surface of the boot. Differing electrical polarities are applied to the inner and outer surfaces of the piezoelectric tube. These electrical polarities are modulated to excite the piezoelectric tube to resonate at a frequency controlled by the inertia of the liquid in the passageway and the mass of the liquid inside the piezoelectric tube.

Method and apparatus for generating low frequency acoustic energy waves

Acoustic well logging method and system employing a bender-type transducer as a point source of an acoustic shear wave. The bender-type transducer includes opposed unrestricted planar surfaces mounted within a liquid filled compartment within the tool. The unrestricted surfaces of the transducer are spaced longitudinally along the axis of the tool and exposed to the coupling liquid. One or more bender-type transducers may also be employed as acoustic receivers in the tools. The active surfaces of the receiving transducers are oriented in substantially the same direction as the active surfaces of the transmitting transducer.

Shear wave acoustic logging system

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.

Method and system for producing a PPI display

A borehole logging system employs a compressional wave transmitter and a shear wave transmitter. The transmitters are alternately fired to impart compressional and shear waves into the formations surrounding the borehole. A bender-type receiver, spaced apart from the transmitter in the borehole is alternately gated so that the voltages across its pair of piezoelectric planar surfaces are subtracted during the expected time period of symmetrical motion of the receiver to provide a compressional wave output and added during the expected arrival time period of unsymmetrical motion of the receiver to provide a shear wave output.

Acoustic well logging device for detecting compressional and shear waves

A method of identifying potential low water cut hydrocarbon producing zones in sandstone formations lacking significant cementation and having relatively high log-indicated water saturations, implying the presence of significant amounts of unbound water. A formation is logged in a conventional fashion to determine porosity and fractional water saturation along the formation. A linear relation between porosity and water saturation is then derived, preferably by linear regression on pairs of log-indicated porosity and fractional water saturation values, each pair being taken from a different depth along the formation. Irreducible water saturation at any point along the depth of the formation is estimatable from the derived linear function and the log-indicated porosity of a formation at that depth. Potential low water cut pay zones are located by determining irreducible water saturation for at least a length of the formation using the aforesaid linear relation and log-indicated porosity values of the formation along said length, in the manner just described. The irreducible water saturation values thus determined are compared with the log-indicated fractional water saturation values obtained along the same length of the formation, preferably by displaying the two sets of values together in a common log as a function of depth. Depths where the irreducible water saturation approximates or exceeds the log-indicated fractional water saturation are zones in which any hydrocarbons produced will be water free or have a low water cut. The derived linear relationship may also be used with pairs of log-indicated porosity and fractional water saturation values obtained elsewhere within the same formation to identify potential low water cut pay zones at those locations.

Method of locating potential low water cut hydrocarbon reservoirs in

Disclosed is a method for determining the permeability of a formation which includes the steps of traversing a bore-hole with a tool having a means for transmitting low frequency acoustic energy. The transmitting means is pulsed and the acoustic energy is detected by a first wide band receiver having a frequency response of between at least 0.1k hertz and 30k hertz. The receiver is coupled to the transmitting means only by means of a cable which has a length exceeding about 5 feet and preferably a length of about 15 feet. The amplitude of tube waves detected by the receiver is determined at a plurality of locations in the bore-hole. The change of amplitude in tube waves at various of these locations provides a measure of permeability. The receiver employed preferably comprises a cylinder of piezoelectric material having end plates at the ends of the cylinder and a passageway through one of the end plates which transmits ambient but not dynamic pressure changes.

Determination of formation permeability from a long-spaced acoustic log

A method of identifying potential low water cut hydrocarbon producing zones of a formation having significant water saturation (i.e. about 50% or more of the available pore space). The formation is logged to determine its water saturation. The formation rock is sampled at a level at which the log-indicated water saturation is significant. Sample rock is cleaned of hydrocarbons and saturated with brine. The spin-lattice relaxation time of hydrogen nuclei of the water molecules of the wetted sample is determined using nuclear magnetic resonance techniques and is used to determine the surface area of the sampled rock. An irreducible water saturation of the sampled formation rock is determined from the measured surface area and is plotted with the log-indicated formation water saturation at or at and about the level from which the rock sample was obtained. Levels where the irreducible water saturation approximate or exceed the log-indicated formation water saturation are zones from which hydrocarbons potentially may be recovered without significant attendant water production.

Method of locating potential low water cut hydrocarbon reservoirs

A borehole tool for logging the remanent magnetic field of the earth formations surrounding a borehole includes a coil system having transmitter, receiver, and nulling coils; a phase-sensitive detector connected across the receiver and nulling coils to provide signals representative of magnetic susceptibility; and a detector system having a pair of axially spaced magnetometers, a pair of counters, an oscillator, a comparator, and a transmitter to provide signals representative of the total magnetic field differential between the two magnetometers. An uphole receiver compares differentials in the magnetic susceptibility measurements between two positions in the borehole with the total magnetic field differential between the same two positions as an indication of the earth's remanent magnetic field.

Well logging system for measuring remanent magnetic fields in the earth

An acoustic velocity logging tool employs a transmitter and a pair of receivers. Acoustic pulses from the transmitter pass through the formation surrounding the borehole to the receivers. The received signals, along with control signals, are transferred to an uphole recording system. A record unit operates to apply these receiver and control signals to a magnetic tape recorder. A playback unit transfers the recorded receiver signals to the intensity modulation input of a cathode-ray oscilloscope and, in response to the recorded control signals, applies a trigger pulse to the sweep input of the cathode-ray oscilloscope, successive sweeps of the cathode-ray oscilloscope being intensity modulated alternately by the recorded receiver signals of the pair of receivers. A film recorder makes a continuous film recording of the receiver signals as they appear as variable-density traces on the face of the cathode-ray oscilloscope to provide a two-receiver, variable-density recording. A .DELTA.T unit computes the interval traveltime of the acoustic pulses between the two receivers as represented by the two variable-density recordings. A plotter produces a continuous curve of this interval traveltime in correlation with the depth of the receivers in the borehole.

Two-receiver, variable-density logging system

An acoustic velocity logging tool employs a transmitter and a pair of receivers. Acoustic pulses from the transmitter pass through the formation surrounding the borehole to the receivers. The received signals, along with control signals, are transferred to an uphole recording system. A record unit operates to apply these receiver and control signals to a magnetic tape recorder. A playback unit transfers the recorded receiver signals to the intensity modulation input of a cathode-ray oscilloscope and, in response to the recorded control signals, applies a trigger pulse to the sweep input of the cathode-ray oscilloscope. A film recorder makes a continuous film recording of the receiver signals as they appear as variable-density traces on the face of the cathode-ray oscilloscope.

Acoustic velocity logging system

An acoustic velocity logging tool employs a transmitter and a pair of receivers. Acoustic pulses from the transmitter pass through the formation surrounding the borehole to the receivers. The received signals, along with control signals, are transferred to an uphole recording system. A record unit operates to apply these receiver and control signals to a magnetic tape recorder. A playback unit transfers the recorded receiver signals to the intensity modulation input of a cathode-ray oscilloscope and, in response to the recorded control signals, applies a trigger pulse to the sweep input of the cathode-ray oscilloscope, successive sweeps of the cathode-ray oscilloscope being intensity modulated alternately by the recorded receiver signals of the pair of receivers. A film recorder makes a continuous film recording of the receiver signals as they appear as variable-density traces on the face of the cathode-ray oscilloscope to provide a continuous two-receiver, variable-density recording.

Growing community of inventors

Dallas, TX, United States of America

Joseph Zemanek, Jr