Abstract: A method for characterizing a fluid sample withdrawn from an earth formation. The method includes performing nuclear magnetic resonant spin echo measurements on the fluid sample at a nuclear magnetic resonant frequency of carbon-13. Amplitudes of the spin echo measurements are summed. The summed measurements are spectrally analyzed. The fluid is characterized by determining whether aromatic hydrocarbons are present by measuring an amplitude of the spectrally analyzed spin echo measurements at about 130 part per million shift from the carbon-13 frequency. The fluid is also characterized by determining whether aliphatic hydrocarbons are present by measuring an amplitude of the spectrally analyzed spin echo measurements at about 30 parts per million frequency shift.

Abstract: A system and method for controlling the transmitted signal for use in a well logging tool, using an iterative method (preferably the method of steepest descent) such that the transmitted signal more closely resembles a desired waveform.

Abstract: A method for determining intrinsic transverse relaxation time of a first mobile phase in a porous medium using nuclear magnetic resonance measurement sequences. The sequences are measured at first and second wait times. At least two different interecho spacing times are used for each wait time. The first and second wait time are selected to provide different magnetization recoveries of the first phase, and are selected to be longer than the longitudinal relaxation time of a second mobile phase. For the measurements made at the first interecho spacing time, components of signals in the measurements corresponding to the first phase are separated from components corresponding to the second mobile phase by determining differences between the signals measured at the first and at the second wait times. The step of separating is performed for each of the interecho spacing times.

Abstract: The total porosity of a subterranean formation is calculated by summing the effective Porosity and the clay bound water (CBW) porosity. With the invention described in this patent, the distortion effects of clay bound water (CBW) porosity on the measurement of total porosity is filtered out. The effects will be more significant in slialy sand where the CBW porosity component of total porosity is abundant. The correct NMR transverse relaxation time (T.sub.2) spectra distribution is essential to a determination of capillary bound fluid (BVI) partial porosity and the Spectral Bulk Volume Irreducible (SBVI) model. The same data correction concept can be applied to make a meaningful comparison of well logs or laboratory core NMR data that are obtained with different interecho time (TE) sampling periods.

Abstract: A differential array instrument for determining selected parameters of an earth formation surrounding a borehole, including an instrument mandrel carrying a single source electrode for injecting an electrical current of a predetermined value into the formation surrounding the borehole, and an array of a plurality of measurement electrodes uniformly and vertically spaced from said source electrode along the instrument mandrel. A predetermined group of the uniformly and vertically spaced electrodes are adapted to derive first and second difference potentials between the predetermined group of electrodes, wherein successive ones of a plurality of the predetermined group of selected measuring electrodes uniformly and vertically spaced at increasing distances from the source electrode axially of the borehole are adapted to derive a plurality of the first and second difference potentials between the predetermined group of electrodes.

Abstract: A single well transient electromagnetic ("TEM") apparatus and method is disclosed. The invention includes a wireline logging tool adapted for disposition in a borehole drilled in earth formations that has mounted thereon an electromagnetic transmitter and electric field transmitter for applying electromagnetic energy to the formation that will maximize the radial depth of penetration of the energy into the formation. The logging tool further includes an electromagnetic receiver and electric field receiver for detecting the electric field and magnetic field components created in the formation by the TEM transmitter. The electromagnetic transmitter and receiver preferably comprise three-axis electromagnetic coils, and the electric field transmitter and receiver preferably comprise three-axis electric dipole antenna elements. The tool may employ an array of the TEM transmitters and TEM receivers spaced axially along the tool in the borehole.

Abstract: A method of determining selected parameters of an earth formation surrounding a borehole by first, obtaining at least one induction logging measurement of the selected parameters in a first predetermined volume of the formation surrounding the borehole having known first radial and vertical dimensions, then obtaining at least one galvanic logging measurement of the identical selected parameters in a second predetermined volume of the formation surrounding the borehole having known second radial and vertical dimensions that overlap the first radial and vertical dimensions of the first predetermined volume, whereby the overlapping volumes form a representative common volume of the formation, and then combining the induction and galvanic logging measurements using an inversion technique to obtain a measurement of the selected parameters of the earth formation surrounding the borehole in the representative common volume of the formation.

Abstract: This invention describes a methodology to image features using an array of multiple piezo-electric elements which employs the selective use of mechanical and electronic beam focusing, electronic beam steering and amplitude shading to increase resolution and overcome side lobe effects. This invention introduces a novel signal reconstruction technique utilizing independent array element transmission and reception, creating focusing and beam steering. Application of the methodology can be used in wireline, measurement while drilling, pipe and pipeline and medical applications. Applications include, but are not limited to Bore hole Caliper, Bore hole Geometry, Bore hole Imaging, Casing Inspection, Cement Evaluation and Volumetric Scanning Applications (e.g. Fluid, Behind Casing and Open Hole). The configuration of the transducer array is preferably cylindrical, but may be conical, biconical, convex, concave or may take the form of a number of suitable geometric configurations.

Abstract: An electromagnetic well logging tool for imaging the electrical characteristics of a borehole. A tool inserted into the borehole includes the appropriate mechanical apparatus to align a plurality of transmission lines adjacent to the borehole wall without requiring direct electrical contact. Electrical circuitry applies a step or impulse voltage on one end and samples the reflections at the same end of each transmission line, where the reflections indicate the magnitude of any changes of dielectric constant of the material of the borehole wall. The transmission lines are preferably angled relative to the center line of the borehole for a complete mapping of the circumference. The tool is moved at a desired speed through the portion of the borehole where measurement is desired. The sampling rate of the reflections depends on the desired speed of the tool and the desired resolution of the measurements.

Abstract: A sidewall coring tool for wireline use in an earth bore hole is provided which includes an elongated tool body adapted for suspension within the bore hole by the wireline cable at a selected depth, low speed high torque rotary coring bit apparatus mounted within the elongated tool body and cooperating therewith for advancing and retracting a rotary coring bit transversely therefrom for drilling and recovering a large core sample from the sidewall of the bore hole, and decentralizing arm apparatus mounted in the tool body on the side opposite the side of the body from which the rotary coring bit is advanced, the decentralizing arm apparatus spaced above and below the location of the rotary coring apparatus for deploying decentralizing arms from the tool body into contact with the bore hole walls and forcing the side of the tool body from which the rotary coring bit will be advanced into contact with the bore hole wall and for maintaining the tool body in rigid contact during the coring operation.

Abstract: Method and apparatus are disclosed for determining the water cut of an oil-water flow in a wellbore having a known deviation angle less than 90. A first step includes generating a set of predicted response curves where each response curve relates discrete selected values of the water cut to test values representative of a value of the flow mixture functionally related to measured responses of a selected logging instrument capable of distinguishing between the water and oil phases of the flow mixture for a selected oil-water total flow rate and at a borehole deviation within a selected range of deviation values that include the known borehole deviation. Then the selected logging instrument combination is introduced into the borehole for measuring the total flow rate of the oil-water mixture and the values representative of the responses of the selected logging instrument distinguishing between the oil and water phases of the oil-water mixture.

Abstract: A production logging tool for use in deviated wellbores is provided having an elongate tool body and an elongate sensor probe that is capable of lateral movement relative to the tool body. The sensor probe is connected to the tool body by a mechanism serving to deploy the sensor probe such that it is oriented across the wellbore. The tool body has a defined weight and the probe has a weight less than the defined weight, thus causing gravity induced orientation of the sensor probe so as to extend from top to bottom of the fluid passage for sensing all phases of the fluid present therein. The sensor probe is typically of elongate configuration and may support a single elongate sensor or a plurality of independent similar or dissimilar sensors arranged in spaced relation along the length of the probe. Orientation of the sensor probe across the borehole is accomplished mechanically by coil or leaf springs or by a hydraulically or pneumatically powered mechanism or by an electric motor driven mechanism.

Abstract: A method and apparatus for conducting in situ tests on a subsurface earth formation of interest which is traversed by a wellbore. A wireline formation testing instrument is positioned at formation depth and a sampling probe thereof is extended into fluid communication with the formation and isolated from wellbore pressure. Utilizing a hydraulically energized double-acting bi-directional piston pump and by valve controlled selection of pumping direction testing fluid such as completion fluid may be pumped into the formation through the sampling probe either from fluid reservoirs of the instrument or from the wellbore. After reversing the operating and control valving of the pump and instrument, the piston pump is utilized to extract formation fluid from the formation and pump it to sample tanks of the instrument, pump it into the wellbore or subject it to controlled pressure for real time formation testing and for formation characterization.

Abstract: An apparatus and method for digitally processing signals received by an induction logging tool having a transmitter and a plurality of receivers. An oscillating signal is provided to the transmitter, which causes eddy currents to flow in a surrounding formation. The magnitudes of the eddy currents are proportional to the conductivity of the formation. The eddy currents in turn induce voltages in the receivers. The received voltages are digitized at a sampling rate well above the maximum frequency of interest. The digitizing window is synchronized to a cycle of the oscillating current signal. Corresponding samples obtained in each cycle are cumulatively summed over a large number of such cycles. The summed samples form a stacked signal. Stacked signals generated for corresponding receiver coils are transmitted to a computer for spectral analysis. Transmitting the stacked signals and not all the individually sampled signals, reduces the amount of data that needs to be stored or transmitted.

Abstract: A method and apparatus for acquiring a plurality of sidewall cores from an earth formation intersected by a wellbore while a coring tool is located downhole. A sidewall coring tool is provided having an internal core receptacle for receiving and storing sidewall cores in serial orientation. The coring tool incorporates a movable bit box providing rotary support and linear coring and retracting movement of a rotary coring bit. A bit box tilting and rotation actuator is incorporated within the coring tool for achieving breaking at the core sample from the formation and for selectively positioning of the bit box and rotary coring bit at a coring position where the bit is oriented in normal relation with the axis of the wellbore and a core ejecting position where the rotary coring bit is positioned in registry with the internal core receptacle for deposit of cores in serially oriented relation therein.

Abstract: A method and apparatus for downhole formation testing is provided for acquisition of a phase intact sample of connate fluid by direct or indirect pumping for filling of pressure containing sample tanks that are removable from a formation testing and sampling instrument for phase intact transportation to a laboratory facility. One or more fluid sample tanks contained within the instrument are filled with connate fluid samples in such manner that during filling of the sample tanks the pressure of the connate fluid is maintained within the predetermined range above the bubble point of the fluid sample. The sample tank incorporates an internal free-floating piston which separates the sample tank into sample containing and pressure evacuation chambers. During indirect pumping a positive displacement piston pump draws fluid from the pressure evacuation chamber and permits formation pressure to shift the separator piston as the first variable volume chamber is filled with a connate fluid sample.

Abstract: A method and apparatus is provided for use in connection with a downhole formation testing instrument for acquisition of a phase intact sample of connate fluid for delivery via a pressure containing sample tank to a laboratory facility. One or more fluid sample tanks contained within the instrument are pressure balanced with respect to the wellbore at formation level and are filled with a connate fluid sample in such manner that during filling of the sample tanks the pressure of the connate fluid is maintained within the predetermined range above the bubble point of the fluid sample. The sample tank incorporates an internal free-floating piston which separates the sample tank into sample containing and pressure balancing chambers with the pressure balancing chamber being in communication with borehole pressure.

Abstract: A propulsion apparatus is provided for attachment to a selected tool for propelling and positioning the tool in a tubular member in response to fluid pressure in the tubular member and includes a tubular mandrel terminating in a lower free end, a tubular sleeve disposed over the mandrel and adapted for coaxial sliding movement with respect thereto, a cup assembly mounted on the sleeve and cooperating therewith and with the fluid pressure exerted within the tubular member for translating fluid differential pressure developed across the cup assembly into preselected propelling forces, and sleeve retaining means for cooperating with the sleeve and mandrel for positioning and retaining the sleeve in a first position with respect to the mandrel and transmitting the propelling forces to the mandrel and attached tool for propelling and positioning the tool to selected locations within the tubular member.

Abstract: The borehole formation model is built by stacking in a spaced relationship selected glass plates to simulate the formation. Each glass plate has a circular hole in the center to simulate the oil or gas borehole. The hole can be sized in different sets to simulate various borehole diameters and for accommodating casing/cement sections for simulating cased boreholes. The glass plates are supported by plastic spacers. The spacers are sized to provide a matrix section having uniform distances between layers. The "stacked" glass/spacer matrix provides only glass for simulating the formation "pore space". The glass plates have a uniform thickness, and the porosity of the simulated formation can be changed by changing the thickness of the plastic spacers. After stacking the glass plates, a "borehole" is constructed by inserting a thin stainless steel tube through the center holes of the glass stack and sealed at the bottom.

Abstract: In an electromagnetic propagating antenna circumferential groove disposed in an MWD resistivity tool mandrel and normally sealed with an epoxy resin non-conducting material forming an annular ring disposed in each of the plurality of circumferential grooves through which the electromagnetic energy from the antenna coil will propagate from the mandrel, each of the circumferential grooves comprises a pair of sidewalls interconnected by an annular flat base portion, each of the sidewalls further having disposed therein a plurality of circumferentially-spaced and longitudinally-disposed slots of uniform size having an open end communicating with each of the sidewalls and a closed end terminating longitudinally spaced from each of the sidewalls for forming a "zipper slot" configuration to the plurality of circumferential grooves, wherein the surface area of all of the plurality of zipper slots is preselected for cooperating with the surface area of each of the circumferential grooves for increasing the surface are