Abstract: A neutron detector sensitive principally to epithermal neutrons is disclosed. In a preferred embodiment of the invention, a neutron counter is substantially surrounded by a reflector composed of material having a high neutron scattering cross section. The reflector is then wrapped in a shield which is composed of a thermal neutron absorber. In a specific embodiment of the invention, the counter, reflector and shield are mounted inside a neutron moderator which can be composed of plastic.

Abstract: A method of reducing effects of noise in seismic signals generated by a plurality of seismic sensors at spaced apart locations from a seismic source is disclosed. Each of the signals is represented by a signal trace in a record section. The method includes the steps of isolating noise in the signal traces, time aligning corresponding portions of the noise in the traces thereby generating time-aligned noise traces, stacking the time-aligned noise trace to generate a stacked noise trace, replicating the stacked noise trace at each corresponding trace position in the record section, restoring the replicated traces to the original trace time positions by reversing the step of time-aligning to generate noise signature traces, comparing the noise signature traces to corresponding signal traces to generate filters which substantially minimize a measure of the difference between the noise signature traces and the signal traces.

Abstract: A liner for a shaped charge formed from a mixture of powdered tungsten and powdered metal binder. The liner is formed by compression of the mixture into a substantially conically shaped solid body. In a preferred embodiment of the invention, the mixture comprises approximately 80 percent by weight of tungsten and 20 percent of the powdered metal binder. In a specific embodiment of the invention, graphite powder is intermixed with the powdered metal binder and tungsten to act as a lubricant. The powdered metal binder preferably comprises a malleable, ductile metal such as lead, bismuth, tin, zinc, silver, antimony, cobalt, nickel or uranium.

Abstract: The invention is a method of determining the flow regime of fluid having more than one phase flowing in a conduit. The method includes the step of positioning a sensor in the conduit, the sensor generating measurements capable of discriminating more than one phase in the fluids, generating measurements from the sensor for a period of time, characterizing the measurements with respect to changes in magnitude of the measurements occurring during the period of time, and comparing the characterized measurements to similarly characterized measurements of a similar sensor positioned within flow streams having known flow regimes.In a preferred embodiment of the invention, the characterization of the measurements includes performing a variability analysis of the measurements.

Abstract: The invention is a system for conducting a geophysical survey in a wellbore, comprising a battery-powered, self-contained borehole seismic receiver which internally digitizes and records an electrical signal generated by a transducer in the receiver, and a surface control unit which records the acoustic signature of the seismic energy source deployed at the earth's surface, controls the firing of the seismic source, and correlates the recording in the receiver to the recording of the source to determine the travel time of the seismic energy through the earth.

Abstract: The present invention is a differential pressure fluid density production logging tool. The tool comprises an elongated housing adapted to traverse a wellbore. The housing has ports in hydraulic communication with the wellbore at spaced apart locations. The tool also comprises a differential pressure transducer having two inputs, a selective valve, and a reference tube filled with a liquid having a known density. The valve is selectively operable to shunt the inputs of the transducer, to connect the reference tube across the inputs of the transducer to calibrate the transducer, and to connect the ports across the inputs of the transducer to enable measurement of the fluids in the wellbore.

Abstract: The invention is an apparatus for initiating a wellbore perforator comprising a first firing head for generating a first explosive signal when a first actuation signal is applied to the first firing head, a second firing head for generating a second explosive signal when a second actuation signal is applied to the second firing head, a first means for transferring the first explosive signal to shaped charges in the perforator including a first bulkhead interposed between the shaped charges and the first means for preventing transfer of low order initiation of the first means to the shaped charges, and a second means for transferring the second explosive signal to the shaped charges including a second bulkhead interposed between the shaped charges and the second means for preventing transfer of low order initiation of the second means to the shaped charges.

Abstract: An apparatus for withdrawing fluid from an earth formation comprising an elongated housing, a first inflatable elastomeric seal adapted to expansively fill an annular space between the housing and the wall of a wellbore. The seal includes axially spaced seal lips protruding from a surface of the seal. The seal lips circumscribe the seal and define a flow channel therebetween. The flow channel includes radially spaced filler blocks which divide the channel into radial segments. Each segment further includes a flow port. The apparatus includes means for inflating the seal. The apparatus includes valves connected to each of the flow ports for connecting selected flow ports to an intake of a fluid pump and connecting selected other flow ports to a discharge port of the pump. The pump is operable in conjunction with the valves to withdraw fluid from selected flow ports and to discharge fluid into other flow ports.

Abstract: The present invention is a sample tank for storing and transporting a fluid sample withdrawn from an earth formation by a formation fluid sampling tool. The sample tank includes a storage cylinder adapted to withstand high internal pressure. The storage cylinder is selectively hydraulically connected to the sampling tool for conducting the fluid sample into the storage cylinder. A fusible metal substantially surrounds the storage cylinder. The fusible metal has a melting temperature not more than the temperature of the fluid sample, so that solidification of the fusible metal maintains the fluid sample substantially at the melting temperature of the fusible metal during solidification of the fusible metal as the tool is withdrawn from the wellbore and cooled. The fusible metal is surrounded by an outer housing which contains the fusible metal when it is in a liquid state.

Abstract: A method of determining resistivity of an earth formation penetrated by a wellbore having conductive casing. The preferred embodiment includes inserting a sonde into the wellbore, the sonde having a plurality of electrodes at axially spaced apart locations adapted to electrically contact the casing, applying electrical current between a first and a second one of the electrodes and measuring the current, measuring a first voltage between a first pair of electrodes axially disposed between the first and second electrodes and measuring a second voltage between a second pair of electrodes also axially disposed between the first and second electrodes and disposed externally to the first pair to determine casing resistance in between the pairs of electrodes. A second difference between the first and second voltages is also measured.

Abstract: A method of determining the acoustic propagation velocity of an earth formation penetrated by a wellbore by processing signals from an array acoustic wellbore logging tool. The tool includes a transmitter and a plurality of receivers axially spaced apart from the transmitter. The method includes the steps of combining signals generated by ones of the receivers in response to acoustic energy propagated through the wellbore from the transmitter, to generate a synthesized signal corresponding to another one of the receivers. The step of combining includes time shifting signals from the ones of the receivers by an amount corresponding to a predetermined velocity for each propagation mode and the axial distance between the ones of receivers and the other receiver. The synthesized signal is compared to the signal generated at the other receiver in response to the acoustic energy to determine a degree of correspondence between the synthesized signal and the received signal.

Abstract: The present invention is a system for determining the depth of a logging tool attached to a cable extended into a wellbore penetrating an earth formation. In a preferred embodiment, the system includes a circuit for generating a measurement of phase shift in a sinusoidal electrical signal traversing the cable, the phase shift corresponding to a length of the cable. The system also comprises an accelerometer disposed within the tool and electrically connected to a bandpass filter and thence to a double integrator connected to the bandpass filter. The integrator calculates displacement of the tool coaxial with the wellbore. The phase shift measurement is filtered in a low pass filter. The low pass filter and the bandpass filter comprise at least some amount of bandpass overlap. The integrator output is used to generate a scale factor, which is applied to the filtered phase shift signal. The scaled phase shift signal is combined in a computer with a signal generated by a depth encoder.

Abstract: The invention is a firing circuit for an exploding bridgewire explosive detonator which is activated only by application of an alternating current of a preselected frequency. The firing circuit comprises a bandpass filter, a voltage multiplier, and a discharge circuit.The invention can be configured to selectively detonate a plurality of exploding bridgewire detonators by assembling a plurality of firing circuits for each exploding bridgewire, each firing circuit having a bandpass filter with a different preselected frequency.

Abstract: The invention is a system for determining the epithermal neutron decay rate of an earth formation penetrated by a wellbore.

Abstract: A method for determining density of a formation. The method includes irradiating the formation with gamma rays having energy consistent with Compton scattering. Gamma rays are measured at axially spaced apart locations. Two of the axially spaced apart locations are at an equal distance and in opposite directions relative to the source of gamma rays. The distance is smaller than the spacing of another one of the spaced apart locations. An apparent density for each spaced apart location is determined from the counts. Differences are calculated in apparent density between each one of the spaced apart locations, and a correction factor is determined for apparent density at each spaced apart location, thereby determining the density of the earth formation. In a preferred embodiment, determining correction factors is performed by a neural network using the differences in apparent density as an input vector.

Abstract: A system for determining formation gas saturation in a cased wellbore which includes a neutron logging tool having a source, a first neutron detector offset towards the wellbore primarily sensitive to the wellbore and a second detector spaced further from the source and offset towards the formation, so that the second detector is sensitive primarily to liquid-filled porosity in the formation. The detectors are encased in a neutron moderator. The system includes a method of determining gas saturation in the formation by measuring count rates at the detectors, generating a wellbore gas saturation from the first detector counting rate, generating a ratio of counting rates of the second and first detectors to generate a value of liquid-filled porosity in the formation, and calculating a gas saturation in the formation by combining the liquid-filled porosity with a measurement of total porosity.

Abstract: The present invention is a system for severing pipe. The system includes an explosively actuated pipe cutter, a pressure actuated initiator, and a means for suspending the cutter and the initiator inside the pipe and pressure sealing the interior of the pipe.In a particular embodiment of the invention, the initiator includes a time delay to enable reduction in pressure applied to the interior of the pipe for actuating the initiator.

Abstract: The present invention is a differential pressure fluid density instrument comprising a housing having a plurality of ports positioned at spaced-apart locations along the housing, a differential pressure transducer, and a valve adapted to selectively connect the transducer across two predetermined one of the plurality of ports. The valve may comprise a three-way solenoid actuated valve. Fluid expansion wells are each connected at one end to a port and prevent wellbore fluids from reaching the differential pressure transducer. The housing includes an inner chamber filled with liquid which may be silicon oil. The chamber includes a standpipe which extends from near the bottom of the chamber, where it is in communication with a lower port, to the top of the chamber. Communication between the chamber and wellbore through the standpipe enables the housing and components disposed within the chamber to be constructed without the need to withstand high differential pressures.

Abstract: The invention is a method of synchronizing a digital telemetry receiver to a digital telemetry transmitter. The method includes the steps of initializing the sampling period of the receiver, measuring the detection time of each signal event detected by the receiver relative to a time window based on the sampling period, accumulating statistics representing the detection times of each of the events, and calculating a refined sampling period based on a linear regression fit of the actual detection time of each event.

Abstract: An apparatus for communicating signals from a well logging tool to a recording unit is disclosed. The logging tool includes a transmitter comprising a source of digital bits representing measurements made by the tool, an encoder connected to the source of digital bits for transforming groups of the digital bits into multivalued symbols, a first in-phase filter and a first quadrature filter connected to the encoder so that first coordinates of the symbols are filtered in the in-phase filter, second coordinates of the symbols are filtered in the quadrature filter, the filters having responses forming a Hilbert transform pair, a digital subtractor connected to the first filters for calculating a difference between outputs of the filters, and a digital-to-analog converter connected to the output of the subtractor for generating signals to be communicated to the recording unit over a communication channel.