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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?.
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PETE 411Well Drilling Lesson 34Horizontal 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? • Control Sand Production • Produce From Thin Reservoirs • Connect Vertical Fractures • Produce Methane from Coal Seams • Increase Injectivity - (steam, water, polymers, etc.)
Production RatesOryx - Austin Chalk Vertical Horizontal Horizontal/Vertical Well Well Production Ratio B/DB/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}
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. (2002)
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/100ft 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.
