PETE 411
Well Drilling
Lesson 34
Horizontal Drilling
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Horizontal Drilling
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Why Drill Horizontal Wells?
Relative Production Rates
Relative Costs
Types of Horizontal Wells
Drilling Problems & Solutions
How Popular is Horizontal Drilling?
Examples
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Why Drill Horizontal Wells?
 Increase Reserves
 Increase Production Rates
 Control Water Production
 Control Gas Production
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Why Drill Horizontal Wells?
 Control Sand Production
 Produce From Thin Reservoirs
 Connect Vertical Fractures
 Produce Methane from Coal Seams
 Increase Injectivity
- (steam, water, polymers, etc.)
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Production Rates
Oryx - Austin Chalk
Vertical
Well
B/D
Horizontal
Well
B/D
Horizontal/Vertical
Production Ratio
12
507
42
15
215
14
5
107
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Production Rates
Drilled 7 wells from 1986 to 1989.
Drilled ~ 85 wells in 1990
Vertical Well Drilling Cost:
235 $/ft
Horizontal Well Drilling Cost: 520-282 $/ft
Cost Ratio:
2.2-1.2
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Drilling Costs
Austin Chalk (1993)
Vertical well
~ $500,000
Recompletion as Horizontal Well ~ $375,000
New Horizontal Well
~
$1,000,000-2,000,000
~ $100+/ft to
$150/ft
{these numbers are rough estimates only}
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Rospo Mare - Italy
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Prudhoe Bay
Vertical Well:
Horizontal Well:
Production Ratio:
Vertical Well:
Horizontal Well:
Cost Ratio:
3000 - 4000 B/D
10,000 - 12,000 B/D
3-4
235 $/ft
520 - 282 $/ft
2.2-1.2
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Long Radius (~1,000-3,000 ft) {~2-6 deg/100 ft}
Medium Radius (140~700 ft) {~8-40 deg/100 ft}
Short Radius (~20-40 ft)
{~1.5-3 deg/ft}
<1,000 ft
~5,000 ft
~8,000 ft
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New Drilling Technology
Measurement While Drilling (MWD)
Directional Surverying and Control
Indentification of Markers (identify zones)
Top Drive
Drill with 90-ft stands instead of 30-ft joints
Circulate while pulling drillpipe out of hole
Rotate drillpipe while pulling out of hole
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New Drilling Technology
Mud Motors
Drill without rotating pipe
Change hole direction while
drilling
Steerable systems
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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
• 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.
• Horizontal wells are often very attractive in
formations with extensive vertical fractures.
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Summary
• The use of horizontal wells has been
growing - worldwide.
• Horizontal wells has increased our
recoverable reserves.
• In the U.S. one rig in ten is drilling
horizontal wells. (1994) (1998)
• Today ~ one rig in fifteen is drilling
horizontal wells. (2002)
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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
(to 6,000 ft +)
Build Rate: ~ 2-6 degrees/100 ft
Build Radius: ~ 1,000-3,000 ft
Length of Horiz. Section: 1,000 - 8,000 ft (1995)
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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
Build Rate:
~ 8 - 20 degrees/100 ft
(up to 40 deg/100 ft in some
cases)
Build Radius:
~ 300 - 700 ft
Length of Horiz. Section: 1,000-6,000 ft
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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
• Use compressive service drillpipe through
the curve if Build Rate > 15 deg./100 ft.
(CS drillpipe has integral wear knots
every ~ 10 ft)
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Short-Radius Wells
Build Rate:
Build Radius:
~ 1 - 3 degrees/ft
~ 20 - 40 ft
Length of Horiz. Section: 200 - 1,000 ft
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Method:
 Two downhole motor designs are 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
 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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Horizontal Well Pair
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Horizontal Well Pair
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Vertical Injection Wells and
Horizontal Production Well
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