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 method for determining the water saturation of subsurface earth formations substantially independent of lithology utilizing electromagnetic energy propagation measurements. The subsurface formations are first logged to obtain base log measurements of the dielectric permittivity of the formations as derived from electromagnetic energy propagation time values. The formations are then injected with a sufficient amount of oil miscible solution containing a surface active agent to displace substantially all the residual fluids from the formations for a radial distance at least equal to the radial zone of investigation. The formations are then injected with a sufficient amount of water to render the zone of investigation substantially 100 percent water saturated. The formations are logged a second time to obtain measurements of the dielectric permittivity of the saturated formations.

Abstract: Method and apparatus for completing sursurface formations traversed by a borehole. A perforating gun and a firing head assembly are run into the borehole on the end of a tubing string. A percussion firing assembly subsequently is lowered through the tubing string and latches into the firing head assembly. To initiate the firing system an impact member is dropped through the tubing string. Should ignition fail to occur the percussion firing assembly can be detached and removed from the borehole. Additional percussion firing assemblies can be lowered into engagement with and removed from the firing head assembly as desired. Further, an electrical firing assembly can be lowered through the tubing string into engagement with the firing head assembly and an electrical control signal used to detonate the perforating gun.

Abstract: The volume of clay within earth formations is determined throughout the vertical extent of a borehole using measurements of the natural gamma rays emitted from these formations comprised substantially entirely of clay. The clay volume determination is used for evaluating the volume of potassium oxide present in the formations. The percent of expandable layers present within the formations is determined, as a direct indicator of potential clay swelling difficulties and thus sensitivity to formation damage sensitivity, based on an extropolated and normalized potassium oxide volume. The percent expandable layers determination is used for determining the cation exchange capacity of the formations.

Abstract: A hydraulic power unit is provided for a downhole instrument of a measurement while drilling system for a well drilling. The hydraulic power unit is enclosed within a drill collar that is connected in the drill string of a rotary drilling rig. An outer body sleeve is rigidly mounted in the instrument drill collar. A fixed inner sleeve is connected to the outer body sleeve in a concentric relation with a longitudinally movable plunger assembly supported therebetween and movable in the telescopic fashion between an extended position and a retracted position to provide hydraulic power fluid for the hydraulically powered circuits of the instrument.

Abstract: An electrical signal representative of the detection of a mechanical coupling within a string of tubular goods is coupled into one input of each of a pair of parallel configured comparators. When the input signal level exceeds the value of complimentary reference levels the respective comparator generates an output signal. The composite output signal from the comparators is converted to a d.c. level which is compared to a fixed reference potential related to the duty cycle of a typical input signal. The comparator output signal is integrated and the peak value of which is stored by a peak detector. In the preferred embodiment the peak value is converted into digital form by an analog-to-digital converter.

Abstract: A computer-based well logging system is disclosed, for acquiring nuclear well log data, including gamma ray energy spectrum and neutron population decay rate data, and providing a real-time preentation of the data on an operator's display based on a traversal by a downhole instrument of a prescribed borehole depth interval.For acquiring energy spectrum data, the system has a multichannel analyzer including a pulse height analyzer and a memory. After a spectral gamma ray pulse signal coming from a downhole instrument over a logging cable is amplified and conditioned, the pulse height analyzer converts the pulse height into a digital code by peak detection, sample-and-hold action, and analog-to-digital conversion. The digital code defines the address of a memory location, or channel, corresponding to a particular gamma ray energy and having a count value to be incremented. After a period of time, the memory channels contain a spectrum of counts per incremental energy band.

Abstract: An improved well logging system and method is provided for deriving and visibly displaying a recordable representation of a comprehensive lithological profile of the earth materials traversed by a borehole. In a particular form of the invention, all logging measurements are derived in digital form and on the same depth-dependent bases, such that measurements taken during one trip through the borehole may be combined or processed with other logging measurements taken during a different trip through the same borehole of interest, such that all of the measurements may then be processed at one time to derive the various lithological indications sought to be provided.An improved monitoring system and technique is further provided, such that those logging measurements and lithological relationships of interest may also be correlatively displayed on a real-time basis with respect to at least some of the logging measurements from which they are derived.

Abstract: In a neutron induced gamma ray well logging instrument, a neutron generator is pulsed at a predetermined clock frequency. Each neutron burst produces inelastically scattered gamma rays and thermal neutron capture gamma rays. Inelastically scattered gamma rays are detected during a time interval coinciding with the neutron source pulsing for a first plurality of neutron bursts. Capture gamma rays are detected during a time interval subsequent to the cessation of the neutron burst for a second plurality of neutron bursts. A detection pulse is transmitted to processing circuitry during each of the detection intervals. Sync pulses generated in the well logging instrument are transmitted to the processing circuitry along with the detection pulses. The sync pulses are used to route the pulse occurring during the inelastic detection interval to one section of a multi-channel analyzer. Similarly, the pulse occurring in the capture interval is routed into another section of the multi-channel analyzer.

Abstract: In a well containing a multi-phase fluid flow regime is disposed an elongated body member with a funnel configuration attached thereto for the purpose of collecting and mixing the multiple fluid phases. An aperture is provided in the body member, proximate to the apex of the funnel configuration, to allow dicharge of the substantially homogeneous mixture of the fluid phases from the funnel through a passage in the body member. A rotor is acted upon by the flow of this mixture and generates a signal representative of the mixture flow rate. A portion of the mixture then enters a chamber in the elongated body member wherein a measurement is made of the degree of penetration of the mixture achieved by gamma radiation, thereby yielding a measurement representative of the density of the mixture. The flow rates and volumetric fractions of each of the individual phases may then be determined in accordance with the mixture density and total flow rate.

Abstract: A reference is established indicating the functional relation between differing proportions of one fluid phase within a mixture of a plurality of fluid phases to the dielectric response of that mixture. Measurements are taken within a well wherein the well fluid consists of multiple fluid phases, of the flow rate, density and dielectric response of the well fluid. The dielectric response measurement is related to the established reference to determine the apparent proportion or volumetric fraction of one fluid phase of the well fluid. The density measurement is utilized to determine the volumetric fraction of the same phase of the well fluid.

Abstract: An elongated body member adapted for coupling to a well logging or perforating instrument in a fixed rotational relation, and formed such that at least a portion of the mass is eccentrically disposed relative to the longitudinal axis of the body member. Located within the eccentric mass of the body member is a recess for retaining one or more magnets. When the orienting decentralizer is introduced into a borehole, virtually any deviation of the borehole from true vertical will cause the longitudinal axis of the body member to tilt and the eccentric mass will cause the decentralizer to rotate about its longitudinal axis and seek equilibrium with the eccentric mass uniformly disposed beneath the tilted axis of the body member, thus rotating the attached logging or perforating instrument to a predictable orientation relative to the lower side of the borehole.

Abstract: Apparatus is provided for collecting a plurality of samples of fluids in earth formations traversed by a well bore. The sampling apparatus includes an elongated body member adapted to carry an extensible and retractible fluid admitting probe which is selectively placed in sealing engagement with potentially producible earth formations. The fluid admitting probe is coupled to a fluid passage which is selectively placed into fluid communication with a fluid sample collection chamber. A pressure control assembly located in the fluid passage intermediate the fluid admitting probe and the sample collection chamber maintains the pressure within at least a portion the fluid passage of a predetermined proportional minimum level of formation pressure during fluid sample collection.

Abstract: An elongated body member having a plurality of crank arms pivotally attached thereto, such crank arms disposed generally symmetrically around the perimeter of the body member. At a first end of each crank arm is a contact pad for maintaining substantial contact with the sidewalls of a borehole. The second end of each crank arm is pivotally coupled to a drive link which is in turn attached to a piston which is longitudinally slidably mounted within the body member. Longitudinal movement of the piston within the body member will result in a corresponding generally lateral movement, either extension or retraction, of the crank arms and thereby of the contact pads attached thereto. A mechanism is provided for allowing the piston to traverse a limited range of longitudinal movement within the body member, a force being exerted upon the piston such that the piston is urged to the bound of such travel which will yield the maximum lateral extension of the contact pads.

Abstract: An apparatus for determining the natural current flow in the casing of a well. The apparatus includes earth surface control and recording equipment connected by a cable to an instrument housing. A casing collar locator on the instrument is used to assist in positioning the instrument in the well casing. A plurality of electrodes on the instrument are contactable with the interior of the casing. The earth surface equipment and the electrodes are used to measure voltages and to pass an electrical current through the casing. Measurements of native voltages in the casing and the change in voltage between two locations in the casing during application of a known current are used to determine the casing's resistance at that location in the well and the native current flow between the well casing and the earth formation throughout the well.

Abstract: A method is provided for determining the natural current flow in the casing of a well. The method includes measuring the native voltage between two locations in the casing during natural current flow conditions. A known electrical current is then passed through the well casing and the voltage between the two locations is measured again. The casing resistance between the two locations is then determined from the voltage measurements and known electrical current. The native current flow in the casing is then determined from the native voltage measurement and the casing resistance.

Abstract: In a gamma ray well logging instrument, a neutron generator is pulsed at a predetermined rate. Each neutron burst produces gamma radiation resulting from inelastic scattering and neutron capture. The detected gamma radiations are detected by a detector system within the logging instrument. The detected pulses are transmitted to the surface electronics where pulses occurring in the inelastic interval are directed to one section of a multi-channel analyzer and pulses from the capture interval are directed to another section of the analyzer. The use of address decoders and ratio circuits enables an electrical signal to be obtained which represents the ratio of the total capture gamma ray counts within an energy range to the total inelastic gamma ray counts within the same energy range. This electrical signal is representative of the porosity of the subsurface formations being irradiated by neutrons.

Abstract: In a perforating apparatus which has a plurality of explosive charges contained in an elongated tubular perforating gun body and supported on a carrier an energy absorber and explosive charge holder are provided by the present invention. The carrier extends longitudinally in the gun body and has the cases of the explosive charges mounted therethrough with a detonating cord or prima cord positioned at the detonating end portion of the several explosives charges. The energy absorber and explosive charge holder comprises a shaped metallic shield that grasps sides of an explosive charges case to secure it in a rigid fixed position on the carrier. An aperture in this shield permits passage of the detonating cord over the detonating end portion of the charge case and retention of it at that location.

Abstract: An earth borehole instrument having a plurality of contact arms which are forced against the borehole side-walls so as to centralize the instrument in the hole. The contact arms may be either left free to rotate or may be positively locked in a number of non-rotational positions. This locking is done by fixedly engaging an indexing member, which is restricted to movement only in translation as to the instrument shaft, with the contact arms, thereby similarly restricting their movement.

Abstract: Apparatus is provided for collecting a plurality of samples of fluids in earth formations traversed by a well bore. The sampling apparatus includes an elongated body member adapted to carry a telescopically extensible and retractible fluid admitting probe which is selectively placed in sealing engagement with potentially producible earth formations. The fluid admitting probe has a central passage in fluid communication with a first fluid sample chamber and a plurality of outer passages which are selectively communicated with formation fluid sample storage chambers within the body member.