| Patents for E21B 47 - Survey of boreholes or wells (31,352) |
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| 05/16/1991 | CA2029938A1 Electromagnetic source for permanent installation into a well |
| 05/15/1991 | EP0427288A2 Method for measuring fluctuations of ground, and apparatus therefore |
| 05/14/1991 | US5015151 Motor controller for electrical submersible pumps |
| 05/14/1991 | US5015124 Apparatus for directing forward movement of a rod |
| 05/14/1991 | US5014795 Percent grade boring and monitoring apparatus |
| 05/14/1991 | US5014781 Tubing collar position sensing apparatus, and associated methods, for use with a snubbing unit |
| 05/14/1991 | US5014780 Long distance section mill for pipe in a borehole |
| 05/08/1991 | EP0295297A4 Apparatus and method for gravity correction in borehole survey systems |
| 05/08/1991 | CN2076601U Continuous slope measurer |
| 05/07/1991 | US5014010 Dual frequency microwave water cut monitoring means and method |
| 05/02/1991 | EP0424729A2 Liquid level detection |
| 05/02/1991 | EP0424452A1 Plug for well logging operations. |
| 04/30/1991 | US5012412 Method and apparatus for measurement of azimuth of a borehole while drilling |
| 04/30/1991 | US5010965 Self-propelled ram boring machine |
| 04/30/1991 | US5010765 Method of monitoring core sampling during borehole drilling |
| 04/30/1991 | US5010764 Method and apparatus for logging short radius horizontal drainholes |
| 04/24/1991 | EP0424120A2 Borehole pressure and temperature measurement system |
| 04/23/1991 | US5010527 Method for determining the depth of a hydraulic fracture zone in the earth |
| 04/23/1991 | US5010333 Advanced digital telemetry system for monocable transmission featuring multilevel correlative coding and adaptive transversal filter equalizer |
| 04/23/1991 | CA1283304C Measuring flow in a pipe |
| 04/18/1991 | WO1991005135A1 Phase fraction meter |
| 04/17/1991 | EP0422706A2 System and method for monitoring drill bit depth |
| 04/17/1991 | EP0296204A4 Borehole survey system utilizing strapdown inertial navigation |
| 04/16/1991 | US5008664 Apparatus for inductively coupling signals between a downhole sensor and the surface |
| 04/16/1991 | US5007277 Method for forming precision liquid/vapor separated bristle assembly |
| 04/16/1991 | CA1283201C System for acoustically determining the quality of the cement bond in a cased borehole |
| 04/10/1991 | EP0421844A1 Nuclear oxygen activation method and apparatus for detecting and quantifying water flow |
| 04/10/1991 | CN2074814U Carrier for well test instrument |
| 04/09/1991 | US5006845 Gas kick detector |
| 04/09/1991 | US5006250 In-situ biodegradation of halogenated aliphatic compounds as impurities in underground water supply by microbacteria |
| 04/09/1991 | US5006044 Method and system for controlling a mechanical pump to monitor and optimize both reservoir and equipment performance |
| 04/09/1991 | US5005422 Method and apparatus for measuring subsidence |
| 04/09/1991 | US5005406 Monitoring drilling mud composition using flowing liquid junction electrodes |
| 04/09/1991 | CA1282687C Enhanced diameter clean-out tool and method |
| 04/04/1991 | DE3932053A1 Measuring escarpment movement using measuring probe - introduced through guide pipe inserted into ground and accepting target disc and light beam |
| 04/03/1991 | EP0208770B1 Fluid means for data transmission |
| 04/02/1991 | CA1282498C Determination of point of entry of fluid into a cased borehole |
| 03/27/1991 | CN2073933U Hydraulic driving type underground isotopic releaser |
| 03/26/1991 | US5002137 Moling system |
| 03/26/1991 | US5002124 Underground temperature and pressure measuring system for hot-exploiting oil well |
| 03/21/1991 | WO1991004500A1 Pore pressure prediction method |
| 03/21/1991 | WO1991003708A1 Position detecting device for underground excavator |
| 03/21/1991 | CA2066760A1 Pore pressure prediction method |
| 03/20/1991 | EP0417959A2 An assembly for locating the position of an object |
| 03/20/1991 | EP0417936A2 Water-cut monitoring means and method |
| 03/20/1991 | EP0417369A1 Method and apparatus for logging a well below a downhole pump |
| 03/20/1991 | EP0417263A1 Control device and process for drilling by vibration analysis. |
| 03/20/1991 | CN2073474U Monitor on ground for measuring pressure of stratum |
| 03/20/1991 | CN1012092B Steam injection profiling |
| 03/19/1991 | US5001342 Radioactive tracer cement thickness measurement |
| 03/19/1991 | US5000272 Self-controlling drill rod |
| 03/19/1991 | CA1281636C Apparatus for use in cementing a casing string within a well bore |
| 03/13/1991 | EP0417001A2 Methods and apparatus for evaluating formation characteristics while drilling a borehole through earth formations |
| 03/13/1991 | CN1049915A Analyzing hydrocarbon reservoir by determining response of that reservoir to tidal forces |
| 03/13/1991 | CA2025088A1 Device for locating a boring machine |
| 03/13/1991 | CA2020529A1 Water-cut monitoring means and method |
| 03/12/1991 | US4998435 Method and apparatus for leak testing of pipe |
| 03/12/1991 | CA1281438C Natural tracer for secondary recovery water injection process |
| 03/12/1991 | CA1281278C Sequential hydraulic fracturing |
| 03/12/1991 | CA1281276C Flow restricting logging tool and method |
| 03/05/1991 | CA1281118C Axial borehole televiewer |
| 02/27/1991 | EP0414334A1 Shock absorber for downhole tool |
| 02/27/1991 | CN2072150U Automatic air gun for echo monitor for oil well |
| 02/27/1991 | CN1011827B Process and device for installing seismic sensors inside petroleum production well |
| 02/26/1991 | US4995465 Rotary drillstring guidance by feedrate oscillation |
| 02/26/1991 | CA1280687C Flapper pad arrangement for logging sonde |
| 02/20/1991 | EP0413628A1 Well testing apparatus |
| 02/20/1991 | EP0413097A1 Device for creating pressure impulses in drilling mud |
| 02/20/1991 | CN2071704U Portable oil well double-suffocated curve diagnostic instrument |
| 02/20/1991 | CN2071703U Wellhead assembly of testing eccentricity for 75.9mm tubing |
| 02/19/1991 | US4995058 Wireline transmission method and apparatus |
| 02/19/1991 | US4994671 Apparatus and method for analyzing the composition of formation fluids |
| 02/19/1991 | US4993503 Horizontal boring apparatus and method |
| 02/14/1991 | DE3926133A1 Test line for rock permeability testing - has measurement bells and packers on tube sections with connecting lines to earth's surface |
| 02/13/1991 | EP0412535A1 Tubing collar position sensing apparatus, and associated methods, for use with a snubbing unit |
| 02/13/1991 | EP0412174A1 Production of bore holes in a given direction |
| 02/13/1991 | CN1011604B Plate current logging device |
| 02/12/1991 | US4992997 Stress wave telemetry system for drillstems and tubing strings |
| 02/12/1991 | US4992787 Computer |
| 02/12/1991 | US4991668 Controlled directional drilling system and method |
| 02/10/1991 | CA2022770A1 Tubing collar position sensing apparatus, and associated methods, for use with a snubbing unit |
| 02/07/1991 | CA2017615A1 Apparatus for measuring weight, torque and side force on a drill bit |
| 02/05/1991 | US4989452 Liquid-level detector |
| 02/02/1991 | WO1991002269A1 Total-field imaging probe |
| 02/02/1991 | CA2059650A1 Total field imaging probe |
| 02/02/1991 | CA2016265A1 Means for varying mwd tool operating modes from the surface |
| 01/31/1991 | CA2019515A1 Method of reducing noise in a borehole electromagnetic telemetry system |
| 01/30/1991 | CN2070355U Dropping-proof device for testing oil/water well |
| 01/30/1991 | CN1011434B Pressure measuring device for submerged electric oil pump well |
| 01/29/1991 | US4987684 Wellbore inertial directional surveying system |
| 01/23/1991 | EP0409446A1 Tool actuator |
| 01/23/1991 | EP0409304A1 Method of monitoring the drilling of a borehole |
| 01/23/1991 | EP0408667A1 Acoustic data transmission through a drill string. |
| 01/23/1991 | CN1011324B Well logging apparatus using uatural current and circular natural potential |
| 01/22/1991 | US4986350 Device for the seismic monitoring of an underground deposit |
| 01/22/1991 | CA1279187C Borehole extensometer for monitoring relative mass displacements |
| 01/16/1991 | EP0408123A2 Geiger-Muller tubes their manufacture and systems comprising them |
| 01/11/1991 | CA2010864A1 Down-hole liquid detecting apparatus |
| 01/10/1991 | WO1991000570A1 Reconfigurable well logging system |
| 01/10/1991 | WO1991000497A1 Device for measuring position of underground excavator |