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PETE 411

Well Drilling

Lesson 34

Horizontal Drilling

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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?

Produce From Thin Reservoirs

Connect Vertical Fractures Produce Methane from Coal Seams

Increase Injectivity - (steam, water, polymers, etc.)

Control Sand Production

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Production RatesOryx - Austin Chalk

Vertical Horizontal Horizontal/Vertical Well Well Production Ratio B/D B/D 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 CostsAustin 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: 3000 - 4000 B/D

Horizontal Well: 10,000 - 12,000 B/D

Production Ratio: 3 - 4

Vertical Well: 235 $/ft

Horizontal Well: 520 - 282 $/ft

Cost Ratio: 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: ~ 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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