(3) 34. Horizontal Drilling

PETE 411 - Well Drilling34. Horizontal Drilling Slide 1

PETE 411

Well Drilling

Lesson 34

Horizontal Drilling


Horizontal Drilling

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



Why Drill Horizontal Wells?

Increase Reserves

Increase Production Rates

Control Water Production

Control Gas Production


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







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


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


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}


Rospo Mare - Italy


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


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


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


New Drilling Technology

Mud Motors

Drill without rotating pipe

Change hole direction while drilling

Steerable systems



Potential Problems in Horizontal Drilling

• Running equipment in and out of hole• drillstring, casing, cables

• Preventing/Remedying differential sticking

• Excessive torque


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


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.


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. (2001)




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)


Method:

• Use conventional directional drilling technology

• Use rigid bottom hole assemblies, motors & bent subs, stabilizers

• or Use Navigation drilling systems with “steerable” drilling motors


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


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)


Short-Radius Wells

Build Rate: ~ 1 - 3 degrees/ft

Build Radius: ~ 20 - 40 ft

Length of Horiz. Section: 200 - 1,000 ft


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.



Horizontal Well Pair


Horizontal Well Pair


Vertical Injection Wells and Horizontal Production Well


(3) 34. Horizontal Drilling

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