TAMU Pemex Offshore Drilling

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TAMU - PemexOffshore Drilling

• Lesson 20
• Horizontal Wells

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Lesson 20 Horizontal Wells

• Why Drill Horizontal Wells?
• Relative Production Rates
• Relative Costs
• Types of Horizontal Wells
• Drilling Problems and Solutions
• How Popular is Horizontal Drilling?

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Austin Chalk
Pearsall Field
Austin
San Antonio
Oil Rig
Austin Chalk
Not to scale
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WHY DRILL HORIZONTAL WELLS?

• Increase Production Rates
• Control Water Production
• Control Gas Production
• Control Sand Production
• Increase Reserves

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WHY DRILL HORIZONTAL WELLS?

• Produce From Thin Reservoirs
• Connect Vertical Fractures
• Produce Methane from Coal Seams
• Increase Injectivity (steam, water, polymers,
  etc.)

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Horizontal Well Drainage Area vertical drainage
area
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7
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30 acres Steady State
Production, Horizontal Well / Vertical Well
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4
3
2
1
0
11
12
10
1
2
3
4
6
7
8
9
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Horizontal Well Length, 100 ft increments
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Vertical Well
Horizontal Well
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Horizontal Drilling Sites
Bryan
Austin
Giddings
Austin Chalk
Houston
Austin Chalk Fields
San Antonio
Pearsall Field
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Horizontal Drilling

• Horizontal wells are often drilled perpendicular
  to vertical fractures in order to intersect and
  drain as many fractures as possible.
• Horizontal drilling greatly reduces the risk of
  bypassing vertically fractured reservoirs.

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Horizontal Drilling

Oil-filled fractures
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PRODUCTION RATES ORYX - Austin Chalk
Drilled 7 wells over a period of 4 years
(1986-1989) Drilled 85 additional wells the next
year (1990)
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ROSPO MARE, ITALY
500
Oil Production, m3/D
Horizontal Well
Slant Well
250
Vertical Well
1984
1986
1982
70m
Water
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PRUDHOE BAY
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2-6 degrees/100 ft 2,800-1,000 ft. radius
Long Radius - Conventional - Directional
20-75 degrees/100 ft 300-125 ft. radius
Medium Radius
1.5-3 degrees/ft 20-40 ft. radius
Short Radius
Pay Zone
400-700 ft
1,000-5,000 ft
1,000-6,000 ft
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NEW DRILLING TECHNOLOGY

• Measurement While Drilling (MWD)
• Directional Surveying and Control
• Identification of Markers
• Identify zones

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Top Drive

• Drill with 90-ft stands instead of 30-ft joints
• Circulate while pulling drillpipe out of hole
• Rotate drill pipe while pulling out of hole

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Mud Motors

• Drill without rotating pipe
• Change hole direction while drilling without
  making a trip to change the BHA
• Steerable systems
• High-torque motors

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Geological Marker
MWD tools are used to locate geological markers
as a well approaches its target so that the
driller can determine the vertical distance
between the bit and target.
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POTENTIAL PROBLEMS IN HORIZONTAL DRILLING

• Running equipment in and out of hole
  drillstring, casing, cables
• Preventing/Remedying differential sticking
• Excessive torque

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POTENTIAL PROBLEMS IN HORIZONTAL DRILLING (contd)

• Cleaning the hole and preventing cuttings from
  settling along the hole bottom
• Controlling weight on bit to achieve and
  maintain directional control
• Cementing casing or liner

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SUMMARY

• Horizontal wells may produce at 3-5 times the
  rate of vertical wells in the same area. (as
  much as 20 times higher in special cases)
• Horizontal wells typically cost 1.5-3 times as
  much as vertical wells in the same area.

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SUMMARY (Continued)

• Horizontal wells are often very attractive in
  formations with extensive vertical fractures.
• The use of horizontal wells is growing-worldwide.
• Horizontal wells will increase our recoverable
  reserves.
• In the U.S. one rig in ten is drilling horizontal
  wells. (1995) 7 today

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LONG-RADIUS WELLS

• Used for achieving large horizontal displacements
  from platforms or drilling pads
• Used for achieving very long horizontal sections
  (4000 ft )

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LONG-RADIUS WELLS (contd)
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METHOD

• Use conventional directional drilling technology
• Use rigid bottom hole assemblies, motors bent
  subs, stabilizers
• Or, use Navigation drilling systems with
  steerable drilling motors

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MEDIUM - RADIUS WELLS
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METHOD

• Use modified long-radius drilling technology
• Use different motors for ANGLE BUILD and ANGLE
  HOLD sections
• Use a TANGENT SECTION between the two build
  sections

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Fig. 1 Medium Radius Angle Build Assembly
String Stabilizer
Dump Valve
Bent Sub
Low-Speed, High-Torque Motor
Kickoff Sub
Upper Bearing Housing with Stabilizer
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SHORT - RADIUS WELLS
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METHOD

• Downhole motor designs are now available
• Drill vertical rathole to identify horizon
• Build angle with special curve-drilling assembly
  with a non-rotating shell that gives curvature to
  the tool

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METHOD (Continued)

• After building angle to horizontal, use a special
  angle-hold assembly
• this consists of two undergauge stabilizers
  behind the bit, and flexible drillpipe

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Fig. 4 Short Radius Curve Drilling Assembly
Drill Pipe (rotating)
Clutch Sub (rotating)
Clutch
Stabilizer
Curved Drill Guide (non-rotating)
Bit Sub (rotating)
Stabilizer
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Multi-Lateral Completion Systems from Baker Oil
Tools
Has Finally Taken Root
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Multi-Lateral Drilling and Completions
Some Things are Designed for Easy Re-entry.
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Complex well geometries boost Orinoco heavy oil
producing ratesOil Gas Journal, Feb. 28, 2000

• Single horizontal lateral
• Gull-wing well
• Stacked multilateral
• Fishbone well
• Gull-wing, fishbone well
• Stacked fishbone well

9oAPI oil. 1.2 1012 bbls in place. 250 109
recoverable
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End of Lesson 20
ATM