Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B29/00—Cutting or destroying pipes, packers, plugs or wire lines, located in boreholes or wells, e.g. cutting of damaged pipes, of windows; Deforming of pipes in boreholes or wells; Reconditioning of well casings while in the ground
  • E21B29/06—Cutting windows, e.g. directional window cutters for whipstock operations
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B7/00—Special methods or apparatus for drilling
  • E21B7/04—Directional drilling
  • E21B7/06—Deflecting the direction of boreholes
  • E21B7/061—Deflecting the direction of boreholes the tool shaft advancing relative to a guide, e.g. a curved tube or a whipstock

Definitions

• the present invention relates to a system for milling a window in a casing of a borehole formed in an earth formation.
• a window is created by fixedly positioning a whipstock having a slanted guide-way, within the casing and guiding a milling tool along the guide-way during milling of the window.
• the downhole force required to progress the milling tool along the guide-way is supplied from surface via a pipe string connected to the milling tool. Fluid is pumped through the pipe string to operate the milling tool and to remove the milling cuttings from the borehole .
• a problem of the conventional system for milling a window in a casing is that the downhole force required to progress the milling tool along the guide-way is insufficiently controllable. This is, for example, due to frictionai forces which counter-act the downward force acting on the pipe string, and due to uncontrolled bending of the pipe string within the casing.
• a system for milling a window in a casing of a borehole formed in an earth formation comprising a milling tool for milling said window, a guiding device for guiding the milling tool along a selected path within the casing during milling said window, the guiding device having means for fixedly arranging the guiding device within the casing, wherein the guiding device is provided with thrust means for thrusting the milling tool along the selected path during milling the window.
• the thrust force necessary for progressing the milling tool during milling is provided from the guiding device rather than from surface.
• the guiding device can be provided with a hydraulic motor or an electric motor receiving power from surface via a suitable control system.
• casing refers to any elongate hollow element which is arranged in the borehole and in which a window is to be milled, such as a cemented casing or a wellbore liner.
• the guiding device is provided with a guide- way defining said selected path and with means for preventing movement of the milling tool transverse to the guide-way. In this manner it is achieved that undesired "walk” of the mill during milling is prevented and that an accurate shape of the window is obtained.
• the selected path extends substantially parallel to the longitudinal axis of the casing.
• the upper window portion is milled by the upper side of the mill and the lower window portion by the lower side of the mill.
• the upper window portion will be biased in one direction (depending on the direction of rotation of the mill) and the lower window portion in the other direction.
• FIG. 1 schematically shows an embodiment of the system according to the invention.
• a borehole 1 has been formed in an earth formation 2 and provided with a steel casing 3.
• the embodiment 4 of the system according to the invention includes a retrievable downhole packer 5 fixedly positioned at a selected location in the casing 3 and provided with an upwardly extending latching element 7 adapted to receive and fixedly hold a support column 9 of a guiding device 11 in a selected orientation.
• the guiding device 11 includes a ramp element 14 rigidly connected to the support column 9 and provided with a secondary support element 16 which is radially extendible against the inner surface of the casing 3.
• the ramp element 14 extends inclined relative to the longitudinal axis of the casing 3 and defines inclined, opposite, directions 20, 22 of a path along which a milling tool 18 is movable, direction 20 being inclined downwardly and direction 22 being inclined upwardly.
• the ramp element 14 is internally provided with a thrust means in the form of a chain (not shown) movable in the directions 20, 22 and an electric motor (not shown) for driving the chain.
• the milling tool 18 has legs 24, 26 which are connected to the chain 14 so that movement of the chain in directions 20, 22 results in corresponding movement of the milling tool 18.
• the milling tool is internally provided with a hydraulic motor (not shown) for driving a mill 27 of the milling tool, the hydraulic motor receiving hydraulic fluid via a coiled tubing 30 extending through the casing 3 to a hydraulic pump (not shown) at surface, the coiled tubing being connected to the hydraulic motor by means of a flexible hose 31.
• the mill 27 has a plurality of outlet nozzles (not shown) for hydraulic fluid from the motor.
• the coiled tubing is provided with a connector (not shown) for connecting the coiled tubing to the guiding device 11 so as to lower and retrieve the guiding device 11 and milling tool 18 through the wellbore 1.
• An electric power supply cable 32 extends from a control unit (not shown) at surface, through the coiled tubing 30 and the hose 31, to the milling tool 18 and from there via one of the legs 24, 26 to the electric motor of the ramp element 14.
• the control unit is provided with controls for selectively moving the chain in direction 20 or 22.
• the control unit includes a control for selectively extending or retracting the secondary support element 16 relative to the inner surface of the casing 3.
• the packer 5 with the latching element 7 connected thereto is fixedly positioned at a selected location in the casing 3 at an orientation corresponding to the desired orientation of the window to be milled.
• the guiding device 11 is connected to the coiled tubing 30 by means of the connector and the combined guiding device 11/milling tool 18 are then lowered by coiled tubing 30 through the casing 3 until the support column 9 latches into latching element 7.
• the control unit at surface is operated to provide a control signal via power supply cable 32 to the guiding device so as to radially extended support element 16 against the casing 3.
• Hydraulic fluid is then pumped through the coiled tubing 30 thereby driving the hydraulic motor so as to rotate the mill 27.
• the control unit at surface is operated so as to move the chain and the milling tool 18 in the direction 20 in order to mill the window.
• the cuttings resulting from the milling operation are entrained and transported away by the hydraulic fluid exiting through the nozzles of the mill 27.
• the control unit is operated to move the milling tool 18 in direction 22 away from the casing 3 and to retract the support element 16.
• the combined guiding device 11/milling tool 18 are then retrieved to surface by means of the coiled tubing 30.
• the packer 5 and latching element 7 are subsequently retrieved to surface in any suitable manner.
• these devices can be integrated into one tool, optionally also including the packer and latching element.
• the thrust means is one of a worm-gear having a spindle extending in the direction along which the milling tool is guided and a hydraulic piston/ cylinder assembly extendible in said direction.
• the milling device can be provided with measuring means for measuring parameters such as the torque delivered by the output shaft of the milling tool, the thrust force delivered by the thrust means, and the position of the milling tool along said path.
• the measuring means is in communication with a data receivin ⁇ station at surface via a data transmission cable extending through a tubing, e.g. the coiled tubing referred to above.

Landscapes

• Geology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mining & Mineral Resources (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• Physics & Mathematics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Earth Drilling (AREA)
• Drilling And Boring (AREA)
• Window Of Vehicle (AREA)
• Glass Compositions (AREA)
• Wing Frames And Configurations (AREA)

Priority Applications (1)

Applications Claiming Priority (4)

Publications (2)

Family

ID=8234910

Family Applications (1)

Country Status (8)

Families Citing this family (1)

Family Cites Families (6)

• 1999
  • 1999-06-27 GC GCP1999193 patent/GC0000060A/xx active
  • 1999-06-30 DE DE69933564T patent/DE69933564T2/de not_active Expired - Fee Related
  • 1999-06-30 CA CA002336326A patent/CA2336326C/en not_active Expired - Fee Related
  • 1999-06-30 EP EP99931252A patent/EP1092077B1/de not_active Expired - Lifetime
  • 1999-06-30 AR ARP990103173 patent/AR019187A1/es active IP Right Grant
  • 1999-06-30 AU AU47817/99A patent/AU751528B2/en not_active Ceased
  • 1999-06-30 WO PCT/EP1999/004700 patent/WO2000001921A1/en not_active Ceased
• 2000
  • 2000-12-29 NO NO20006696A patent/NO317380B1/no unknown

Non-Patent Citations (1)

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