Directional Drilling: deviation from drilling a straight

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Directional DrillingFishing
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Directional Drilling

• Directional Drilling deviation from drilling a
  straight hole.
• Drilled straight to a predetermined depth, and
  then gradually curved.
• Typical curvature 2-3 degrees per 100 of well
  depth
• Drill stem can handle this low angle curvature
  enough to eventually run horizontal.

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Directional Drilling

• Uses
• Offshore
• Development Drilling on Land
• Other Uses
• Tools and Techniques
• Drill Pipe
• Bent Sub and Downhole Motor
• Orienting the Hole

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Directional Drilling (Uses)

• Offshore
• One of the most important uses
• Capability to drill multiple wells from one
  location
• Due to huge expense of constructing a platform,
  this enables operators to capitalize on a single
  investment for multiple producing wells
• Example Gullfaks C platform in the North Sea
• Weighs 1.5 million tons
• Covers 4 acres
• Cost the US 2 billion to build

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Directional Drilling (Uses)
Gullfaks C Platform
Typical North Sea Day
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Drilling Offshore From Land
Rig Location on Land
Pay Zones Offshore
This method is much cheaper and safer than
offshore drilling.
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Directional Drilling (Uses)
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Development Drilling on Land

• Directional drilling on land has several uses
• Avoiding Fault Lines
• Can cause problems in the hole
• Rig Location
• Rivers, Hills, Mountains and other obstructions
• Well orientation in the pay zone
• Operators have increased production by up to 10x
  due to horizontal well orientation.

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Horizontal Drilling
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Other Uses

• Exploration
• Directional allows for deflecting off original
  dry holes to intersect possible pay zones.
• Sidetracking
• Divert around a fish (object lodged in the
  borehole)
• Well Control
• Killing Wild Wells
• Relief Well is drilled directionally to intercept
  the blown out well in order to kill the well by
  pumping mud down hole.

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Tools and Techniques

• Drill Pipe
• Place drill collars at the lower portion of the
  vertical section of the drill string and above
  the lower section of the drill pipe.
• Manufacturers have engineered new types of drill
  pipe especially for horizontal drilling.
• Bent Sub
• Short piece of pipe threaded on both sides and
  bent in the middle
• Typically the bend ranges from 1-3 degrees off
  vertical
• Placed in the drill string between the bottom
  most drill collar and the down hole motor.
• Bent Sub deflects the down hole motor and bit
  off vertical

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Tools and Techniques

• DownHole Motor
• Only Rotates the drill bit, not the drill string
• Shaped like a piece of pipe, can have turbine
  blades or a spiral steel shaft that rotates when
  the drilling mud passes through it.
• Since the bit is attached to the shaft it rotates
  when the shaft turns.

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Directional Drilling Animation

• http//www.youtube.com/watch?vt_AL7rNmWUA
• http//www.youtube.com/watch?vO0kmskvJFt0NR1

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Orienting the Hole

• Inclinometer
• Directional instrument that uses magnetic or
  gyroscopic compass and inclinometer to measure
  the angle of the hole.
• Steering Tool
• Sends directional information up the hole through
  a wire line to a monitor on the rig floor
• Mud Pulse Generator
• A wireless self contained instrument that
  transmits sonic signals up the hole, through the
  drilling fluid in the drill stem, to a readout
  device on the surface.
• MWD
• (Measurement While Drilling) uses the Mud Pulse
  Generator and allows the driller to get
  information from the bottom of the hole without
  stopping drilling at all. Used for straight and
  directional control measurement.

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Fishing

• Fishing
• The term used for retrieving any object from the
  wellbore
• Examples
• Drill Stem (Part or Whole) when it gets stuck
• Smaller pieces of equipment (Also Known as
  Junk)
• Bit cones
• Hand Tools
• Pieces of Steel

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Fishing

• Causes of Stuck Pipe
• Hole Collapses around the pipe
• Pipe gets stuck in a dogleg or key seat
• Pressure can hold the drill collars so securely
  to the wall that no amount of pulling can free
  the pipe.

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Fishing

• Hole Collapses
• Typical causes
• Interstitial Salt Water (Water contained in the
  pores of formation rock) can attract the water in
  the drilling mud.
• If the formation is shale, the water in the mud
  has a tendency to transfer to the shale causing
  it to slough off into the hole.
• Hole eventually fills in and causes the BHA to
  become stuck.

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Fishing

• Key Seat
• Caused by a dogleg (Crooked section of hole)
• Drill pipe leans against the side of the dogleg,
  and as the pipe rotates it digs out a new smaller
  hole in the side of the main borehole.
• When the drill stem is pulled from the hole, the
  tool joint being wider becomes logged in to the
  key seat.

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Fishing

• Pressure
• Mud weight that is to heavy for the formation
  causes a heavy wall cake
• When the drill string is not rotating (ie. Making
  a connection or tripping) it can rest on the
  narrowed wall.
• The pressure from the mud and contact with the
  wall causes the drill string to become stuck
• Typically it can be freed by spotting
  oil/lubricant in the stuck area and then jarring
  on the drill string.
• Drilling Jar or Bumper Sub Special tool that
  provides heavy blows to the drill string upward
  or downward.
• http//www.youtube.com/watch?vv2jvHD897Ssfeature
  related

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Fishing

• Free point Indicator
• Used to locate the stuck portion of pipe
• Indicator induces a magnetic field in the pipe
  and sends a signal to a meter on the surface.
• When the driller picks up on the drill string it
  stretches in places where it is not stuck, this
  causes a strong signal reading (needle moves a
  lot)
• When the driller picks up in the drill string and
  it does not stretch this is indicated by little
  or no movement on the drill string, this is your
  stuck point.
• The depth is then noted.

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Fishing

• String Shot
• Long string like explosive charge that is usually
  run below the freepoint indicator.
• The string is set off helping to loosen the
  threads of the pipe
• Driller turns the rotary table to the left to
  back off the pipe.
• Washover Pipe / Washpipe
• Crew trips in with a special tool while
  circulating and rotating. Tool contains a cutter
  called a rotary shoe that cuts away shale or wall
  cake while latching on to the fish with a
  backoff connector inside the wash pipe.

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Fishing

• Twist Offs
• When a portion of the drill string twists off.
• Typically due to fatigue or damage the pipe
  literally breaks in two.
• Typically not complicated
• Tools used
• Overshot Goes over the fish and grips it firmly
  using a grapple
• Spear Goes inside the fish and grips it (used
  for collars)