1 TAMU - Pemex Offshore Drilling Lesson 20 Horizontal Wells
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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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Not to scaleAustin Chalk
Oil Rig
Austin Chalk
Pearsall Field AustinSan Antonio
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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 Length, 100 ft increments
Horizontal Well Drainage Area
= vertical drainage area
Pro
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n,
Ho
rizo
nta
l W
ell
/ V
erti
cal
Wel
l9
8
7
6
54
3
2
1
01 2 3 4 5 6 7 8 9 10 11 12
= 30 acres
*Steady State
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Vertical Well
Horizontal Well
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Austin Chalk
Bryan
Houston
San Antonio
Pearsall Field
Austin Chalk Fields
AustinGiddings
Horizontal Drilling Sites
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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
VerticalWellB/D
HorizontalWellB/D
Horizontal/Vertical
Ratio 12 507 42
15 215 14
5 107 21
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
Water
Horizontal Well
Vertical Well
Slant Well
Oil
Pro
du
ctio
n,
m3 /D
70m
1982 1984 1986
250
500
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PRUDHOE BAY
Vertical Well: 3,000 - 4,000 B/DHorizontal Well: 10,000 - 12,000 B/DProduction Ratio: 3 - 4
Vertical Well: 235 $/ftHorizontal Well: 520 - 282 $/ftCost Ratio: 2.2 - 1.2
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Long Radius - Conventional - Directional
Medium Radius
Short Radius
2-6 degrees/100 ft
2,800-1,000 ft. radius
20-75 degrees/100 ft
300-125 ft. radius
1,000-6,000 ft400-700 ft 1,000-5,000 ft
1.5-3 degrees/ft
20-40 ft. radius
Pay Zone
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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 (cont’d)
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 (cont’d)
Build Rate: ~2-6 degrees/100 ft
Build Radius: ~1,000-3,000 ft
Length of Horizontal Section:
1,000-7,000 ft
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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
Build Radius: ~ 300-700 ft
Length ofHorizontal Section:
~1,000-5,000 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
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String Stabilizer
Dump Valve
Kickoff Sub
Bent Sub
Low-Speed, High-Torque Motor
Upper Bearing Housing with Stabilizer
Fig. 1: Medium Radius Angle Build Assembly
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SHORT - RADIUS WELLS
Build Rate: ~ 1-3 degrees/ ft
Build Radius: ~ 20-40 ft
Length of HorizontalSection:
400-1000 ft
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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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Drill Pipe (rotating)
Clutch Sub (rotating)
Curved Drill Guide (non-rotating)
Clutch
Stabilizer
Stabilizer
Bit Sub (rotating)
Fig. 4: Short Radius Curve Drilling Assembly
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Has Finally Taken Root
Multi-LateralCompletion Systemsfrom Baker Oil Tools
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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 rates
Oil & 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
AATTMM