PETE 411

Well Drilling Lesson 34 Horizontal Drilling 1

Horizontal Drilling

       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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Vertical Well B/D

Production Rates Oryx - Austin Chalk

Horizontal Well B/D Horizontal/Vertical Production Ratio 12 507 42 15 215 14 5 107 21

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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 14

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 16

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 Angle Hold

sections.

and • 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: ~ 1 - 3 degrees/ft Build Radius: ~ 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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