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| Number | Title | Issue Date |
| 7427863 | Method and system for calculating resistivity of an earth formation Method and system for calculating resistivity of an earth formation. At least some of the illustrative embodiments are methods comprising transmitting a current from a first current source, receiving at least part of the current at a first current return, said first... | 09/23/2008 |
| 7388382 | System for measuring Earth formation resistivity through an electrically conductive wellbore casing An instrument is disclosed for measuring resistivity of Earth formations from within a conductive pipe inside a wellbore drilled through the formations. The instrument includes a plurality of housings connected end to end and adapted to traverse the wellbore. At lea... | 06/17/2008 |
| 7256582 | Method and apparatus for improved current focusing in galvanic resistivity measurement tools for wireline and measurement-while-drilling applications A galvanic resistivity tool with one or more measurement electrodes and guard electrodes, and one or more shielding electrodes. The potential difference between the measurement electrodes and the guard electrodes is controlled to minimize current flow between the me... | 08/14/2007 |
| 7202671 | Method and apparatus for measuring formation conductivities from within cased wellbores by combined measurement of casing current leakage and electromagnetic response A method is disclosed for determining spatial distribution of resistivity of Earth formations surrounding a wellbore having a conductive pipe therein. The method includes measuring resistivity of the Earth formations using measurements of current leakage along the p... | 04/10/2007 |
| 7151377 | Permanent apparatus for monitoring a well by injecting current through the casing into the formations Apparatus for monitoring an underground formation through which a borehole passes, comprises a conductive casing (6) located in the borehole (1) passing through the formation (4); a plurality of sensors (12-1) for measuring an elec... | 12/19/2006 |
| 7109719 | Method and apparatus for azimuthal resistivity measurements in a borehole An azimuthal resistivity logging tool includes one or more pads for making azimuthal resistivity measurements of earth formation. Current from the pads, guard electrodes and a measure electrode are measured while monitoring the voltage difference between pairs of mo... | 09/19/2006 |
| 7098664 | Multi-mode oil base mud imager A multi-mode oil base mud imager for use in non-conductive drilling fluid includes at least one current source—a current return pair, and one or more monitor electrodes not located between the current source and the current return of the current source-current ret... | 08/29/2006 |
| 7042225 | Apparatus and methods for induction-SFL logging A well logging tool includes an induction array stack disposed on a mandrel; an electronic module stack disposed adjacent the induction array stack along a longitudinal axis of the well logging tool; and a shallow electrode array arranged on a housing disposed aroun... | 05/09/2006 |
| 6950749 | Method for resistivity anisotropy determination in near vertical wells A method is disclosed for real-time (well-site) resistivity anisotropy determination using array lateral logs or any other unfocused, lateral-type measurements, and array induction logs or any other focused, induction-type measurements. Near-vertical wells with a de... | 09/27/2005 |
| 6924640 | Oil and gas well tubular inspection system using hall effect sensors An inspection system for detecting flaws in oil and gas well borehole ferromagnetic tubulars. The inspection device operates inside the tubular by first saturating tubular wall with magnetic flux. Flaws in the wall causes flux leakage, and the magnitude of the flux ... | 08/02/2005 |
| 6809521 | Apparatus and method for wellbore resistivity measurements in oil-based muds using capacitive coupling A resistivity device for downhole use with a nonconducting mud injects a current at a frequency sufficiently high to pass capacitively through the mud and a mud cake into the formation. The frequency is further selected so that the impedance due to the dielectric co... | 10/26/2004 |
| 6653839 | Electrical measurement apparatus and method for measuring an electrical characteristic of an earth formation In an electrical measurement apparatus and method for measuring an electrical characteristic of an earth formation, such as in a hole drilled for the exploration for hydrocarbons, a detection portion has an operational amplifier operating in voltage follo... | 11/25/2003 |
| 6426625 | Apparatus for logging the resistivity of a geological rock formation A small diameter tool for measurement of resistivity of geological rock formations, including a complex auxiliary electrode structure which is adjustable in electrode length between deep and shallow mode measurement operations.... | 07/30/2002 |
| 6373254 | Method and apparatus for controlling the effect of contact impedance on a galvanic tool in a logging-while-drilling application The present invention describes a method and apparatus to control the effect of contact impedance on a formation resistivity measurement during a logging-while-drilling operation. The control of contact impedance is accomplished by maintaining a substanti... | 04/16/2002 |
| 5852363 | Methods and apparatus for measuring characteristics of a formation around a borehole using computed focusing A method and apparatus for determining the geometrical characteristics of a well, including insertion of a sonde of elongate shape into the well, the sonde including azimuth electrodes (Aazi), an annular current electrode (A0), and a... | 12/22/1998 |
| 5708369 | Capacitive measuring device A capacitive measuring device with a measuring electrode (3) arranged some distance from a counter-electrode (8), a dielectric material for analysis is arranged between the electrodes (3, 8), and a measuring current (IC) is supplied to the measuring elect... | 01/13/1998 |
| 5396175 | Method and apparatus for evaluating formation resistivity using focused annular and azimuthal electrodes The apparatus includes an annular current electrode (Ao) mounted on a body and guard electrodes (A2, A'2) disposed on the body above and below the annular current electrode. A first measurement current (Io) is emitted by the central current electrode (Ao)... | 03/07/1995 |
| 5343153 | Well logging method and apparatus using passive azimuthal electrodes The invention relates to a logging method and apparatus using passive azimuthal electrodes. The apparatus includes an array of azimuthal electrodes (M'azi) that are circumferentially spaced apart from one another on a body together with two ann... | 08/30/1994 |
| 5268641 | Logging method and apparatus for measuring the Grondingen effect-corrected resistivity of earth formations A logging method for measuring the resistivity of formations having a borehole passing therethrough, in which a logging sonde is suspended inside the borehole by means of a cable, the sonde comprising electrodes for injecting alternating currents into the... | 12/07/1993 |
| 5036283 | Method and apparatus for measuring the resistivity of earth formations using anti-parallel active and passive focussing electrodes The invention relates to a logging method and apparatus for determining the electrical resistivity of an earth formation traversed by a borehole. The resistivity is determined using a measuring pad which has a central electrode operable to deliver a measu... | 07/30/1991 |
| 4659993 | Apparatus including an equipotential housing and plurality of focused current electrodes for electrically logging a well formation at more than one lateral distance from a borehole An apparatus and a method are disclosed wherein simultaneous electrical well logs can be made with a plurality of focused currents emitted from a plurality of electrodes located along a single equipotential surface of a housing. The focused currents are g... | 04/21/1987 |
| 4646026 | Method and apparatus for measuring resistivity of an earth formation A method and apparatus are described for reducing "Groeningen" effect and other anomaly induced errors in resistivity measurements of an earth formation. Such errors are typically noted during resistivity measurements of an earth layer and are generally r... | 02/24/1987 |
| 4594552 | Logging method and apparatus for measuring earth formation resistivity as well as arm mechanism for the same In a well logging sonde having a sonde body and wall engaging pad, the sonde body comprises two conductive sections spaced from one another by an insulating section. The pad and sonde are maintained in a relative longitudinal position such that the focuss... | 06/10/1986 |
| 4584675 | Electrical measuring while drilling with composite electrodes Discloses a two-way telemetry system and method for transmitting data taken at the bottom of a well bore to the earth's surface with one part of the telemetry circuit being the metallic drilling string and with another part of the telemetry circuit being ... | 04/22/1986 |
| 4524325 | Dual guard type resistivity measuring apparatus In a dual guard type resistivity logging apparatus, the improvement having the preferred and illustrated form of a short guard electrode pair for making shallow resistivity measurements in a formation is disclosed; a long guard electrode pair is also inco... | 06/18/1985 |
| 4335353 | Method and apparatus for detecting an anomaly in a resistivity measurement of an earth formation A method and apparatus are described for detecting the presence of an anomaly, such as the Groningen effect, whereby an error in a resistivity measurement of an earth formation layer is noted when such layer is located below a highly resistive bed. The re... | 06/15/1982 |
| 4319192 | Deep and/or shallow electrical resistivity investigation suitable for dual resistivity-induction logging A dual resistivity and induction apparatus for the investigation of earth formations traversed by a borehole, comprises an electrode system, supported on a support member, comprising a central electrode and five pairs of electrodes respectively short-circ... | 03/09/1982 |
| 4282486 | Dual focused resistivity logging method and apparatus with dynamic range reduction Method and apparatus for reducing the dynamic range of measure signals encountered in simultaneously obtaining two focused logs of formation resistivity with different depths of investigation and means for providing the required electrical connections of ... | 08/04/1981 |
| 4278942 | Seal and pressure balance system for an electrode-type logging sonde In the representative embodiment of the invention disclosed herein, an electrical logging tool is arranged to include an axial body around which a plurality of annular electrode members and insulating members are alternately stacked to achieve a particula... | 07/14/1981 |
| 4122387 | Apparatus and method for simultaneously logging an electrical characteristic of a well formation at more than one lateral distance from a borehole A method and apparatus is disclosed wherein simultaneous logs may be made at different lateral distances through a formation from a borehole by guard electrode systems located on a sonde which is lowered into the borehole by a logging cable. A single osci... | 10/24/1978 |
| 4110682 | Well logging apparatus with pad-mounted array of vertical electrodes of different lengths for measuring the resistivity of the flushed zone In accordance with an illustrative embodiment of the present invention, a well logging apparatus uses a narrow wall-engaging pad equipped with an array of vertical electrodes. The length of these electrodes is greater near the edges of the pad than in the... | 08/29/1978 |
| 4019125 | Well logging pad devices having selective differential relief A well logging instrument comprises a focus section having a focus upper guard, a center electrode and lower focus guard. The bottom section of the instrument includes a pad device having electrodes on its borehole wall-engaging surface and adapted to be ... | 04/19/1977 |
