| Patents for E21B 21 - Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor (13,780) |
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| 09/03/1991 | WO1991012987A1 Self propelled probe, particularly for penetrating a powdered material |
| 09/03/1991 | US5045593 Adducts of Phosphatides and Anionic or Cationic Addition Polymers, Fluid Loss Control Agents, Well Drilling Fluids |
| 09/03/1991 | CA2055461A1 Self-propelled probe, particularly for penetrating pulverulent materials |
| 08/29/1991 | WO1991013232A2 Process and apparatus for cleaning particulate solids |
| 08/29/1991 | CA2076636A1 Process and apparatus for cleaning particulate solids |
| 08/28/1991 | CN2083626U Magnetic force slug cleaning and filling device |
| 08/28/1991 | CN2083625U 连续冲砂装置 Continuous sand washing equipment |
| 08/27/1991 | US5042598 Drilling fluid additive sweep cartridge and method |
| 08/27/1991 | US5042296 Method of in-situ testing of a drilling fluid |
| 08/21/1991 | CN2083188U New-type mud-purifying machine |
| 08/20/1991 | US5040621 Flushing means for drilling tools |
| 08/20/1991 | US5040602 Inner string cementing adapter and method of use |
| 08/20/1991 | US5040598 Pulling tool for use with reeled tubing and method for operating tools from wellbores |
| 08/14/1991 | EP0440825A1 Method of re-using slurry in ground improving construction work |
| 08/14/1991 | EP0440747A1 Drilling mud separation system |
| 08/13/1991 | US5038874 Drill bit having a flushing medium channel |
| 08/07/1991 | EP0439484A1 Float collar and plug for use in wells |
| 08/06/1991 | CA1287315C Process for the preparation of an aqueous solution of a heteropolysaccharide |
| 07/31/1991 | EP0438920A1 Dry pneumatic system for hard rock shaft drilling |
| 07/31/1991 | CN1013377B Well-drilling liquid |
| 07/30/1991 | US5035292 Whipstock starter mill with pressure drop tattletale |
| 07/30/1991 | US5035291 Seafloor drilling apparatus |
| 07/30/1991 | US5035285 Electrically conductive |
| 07/24/1991 | EP0437872A2 Method and system for measurement of fluid flow in a drilling rig return line |
| 07/24/1991 | EP0437588A1 Assembly comprising an extension tube and a sleeving conduit inside it. |
| 07/23/1991 | CA1286601C Wellbore cleanout apparatus and method |
| 07/16/1991 | CA1286281C Method for reducing friction in drilling operations |
| 07/10/1991 | EP0436242A1 Method of analysing and controlling a fluid influx during the drilling of a borehole |
| 07/10/1991 | CN2080555U Double spring drainage device for oil pipe |
| 07/09/1991 | US5030365 Of high and low softening points, causticized lignite and a strongly lipophilic surfactant |
| 07/09/1991 | US5029643 Drill pipe bridge plug |
| 07/09/1991 | CA1285746C Organophilic polyphenolic acid adducts |
| 07/03/1991 | EP0435484A1 Method and apparatus for direct high velocity preparation of completion/workover systems |
| 07/03/1991 | EP0435363A1 Method of in-situ testing of a drilling fluid |
| 07/03/1991 | CN1052687A Functional fluids |
| 06/26/1991 | EP0434009A1 Drill bit and method for drilling |
| 06/26/1991 | CN1052530A Pore pressure prediction method |
| 06/19/1991 | CN1052349A Multiple functional treatment agent for well drill liquid and its preparing method |
| 06/15/1991 | CA2032189A1 Method and system for measurement of fluid flow in a drilling rig return line |
| 06/13/1991 | WO1991008375A1 Method and apparatus for cleaning drill cuttings |
| 06/13/1991 | WO1991008275A1 Process for recovery and treatment of a diverse waste stream |
| 06/13/1991 | WO1991008274A1 Process for recovery and treatment of hazardous and non-hazardous components from a waste stream |
| 06/13/1991 | CA2068997A1 Cleaning of cuttings from drilling operations |
| 06/12/1991 | CN2078790U Self-opening drainage, hot-cleaning circulation valve |
| 06/05/1991 | EP0430602A1 Functional fluids |
| 06/05/1991 | EP0429444A1 A drill for rock and concrete |
| 06/05/1991 | CA2030423A1 Method and apparatus for direct high velocity preparation of completion/workover systems |
| 06/04/1991 | US5020612 Wire line core drilling apparatus |
| 06/04/1991 | US5020611 Check valve sub |
| 06/04/1991 | US5020610 Removable filter fluid flow shutoff apparatus |
| 06/04/1991 | US5020594 Method to prevent gas intrusion into wellbores during setting of cements |
| 06/02/1991 | WO1991008371A1 Drilling bit irrigated by a fluid distributed by a fluidic oscillator |
| 06/02/1991 | CA2069953A1 Drilling tool with irrigation system using a fluid distributed by a fluidic oscillator |
| 05/30/1991 | WO1991007568A1 Method for finishing a well |
| 05/30/1991 | WO1991007566A1 Converter |
| 05/30/1991 | CA2073017A1 Converter |
| 05/28/1991 | US5018589 Process for finding the depth of a lost return zone |
| 05/21/1991 | US5016717 Vacuum excavator |
| 05/21/1991 | US5016716 Tubing carried perforating gun with insulation jacket |
| 05/16/1991 | WO1991006743A1 Bottom hole blowout preventer |
| 05/15/1991 | EP0427663A1 Hydraulic drilling device and method for use |
| 05/15/1991 | EP0427018A2 Measuring device for measuring the speed of a fluid |
| 05/14/1991 | US5015128 Rotary drill apparatus |
| 05/09/1991 | CA2029094A1 Hydraulic drilling outfit |
| 05/08/1991 | EP0426232A2 Method of quantitative analysis of drilling fluid products |
| 05/08/1991 | EP0426231A2 Analysis of drilling solids samples |
| 05/07/1991 | US5012876 Rotary drill bit providing separation of liquid from gas |
| 05/07/1991 | US5012866 Drill stem mud wiping apparatus |
| 04/30/1991 | US5010966 Drilling method |
| 04/30/1991 | CA1283631C Method and apparatus for separating particles fluidly suspended in a slurry |
| 04/29/1991 | CA2028053A1 Analysis of drilling solids samples |
| 04/29/1991 | CA2027496A1 Method of quantitative analysis of drilling fluid products |
| 04/24/1991 | CA2001387A1 Bottom hole blowout preventer |
| 04/23/1991 | US5009272 Flow pulsing method and apparatus for drill string |
| 04/16/1991 | US5007488 Drilling nipple gas trap |
| 04/10/1991 | EP0421763A1 The control of 'U' tubing in the flow of cement in oil well casings |
| 04/09/1991 | US5006845 Gas kick detector |
| 04/09/1991 | US5005656 Device in impact machines |
| 04/04/1991 | WO1991004391A1 Method and apparatus for drilling |
| 04/04/1991 | CA2026854A1 Control of 'u' tubing in the flow of cement in oil well casings |
| 04/03/1991 | CN2074360U Elevating agitator for drilling fluid |
| 04/03/1991 | CN2074359U Water supply apparatus |
| 04/03/1991 | CN1050427A Double-layer self-adjustable water distributor |
| 04/02/1991 | US5004051 Method and means for cleansing and storing drill cuttings from drilling operations in the sea bottom |
| 04/02/1991 | US5004048 Cement |
| 03/26/1991 | CA1282053C Borehole drill construction |
| 03/21/1991 | WO1991004500A1 Pore pressure prediction method |
| 03/21/1991 | WO1991003605A1 Method of re-using slurry in ground improving construction work |
| 03/21/1991 | CA2066760A1 Pore pressure prediction method |
| 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 | EP0417009A1 Device and installation for the cleaning of drains especially in an oil production well |
| 03/07/1991 | WO1991001430A3 Lost circulation fluid for oil field drilling operations |
| 03/05/1991 | US4997042 Casing circulator and method |
| 02/26/1991 | CA1280740C Chip sampler |
| 02/22/1991 | CA2023640A1 Drill stem mud wiping apparatus |
| 02/12/1991 | US4991669 Device for controlling the passage of a flushing medium in impact machines |
| 02/12/1991 | CA1280107C Foamed slurry generator |
| 02/08/1991 | WO1991002137A1 Assembly comprising an extension tube and a sleeving conduit inside it |
| 02/07/1991 | WO1991001430A2 Lost circulation fluid for oil field drilling operations |