20. Horizontal Wells

1

TAMU - PemexOffshore Drilling

Lesson 20

Horizontal Wells

2

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?

3

Not to scaleAustin Chalk

Oil Rig

Austin Chalk

Pearsall Field AustinSan Antonio

4

WHY DRILL HORIZONTAL WELLS?

Increase Production Rates

Control Water Production

Control Gas Production

Control Sand Production

Increase Reserves

5

WHY DRILL HORIZONTAL WELLS?

Produce From Thin Reservoirs

Connect Vertical Fractures

Produce Methane from Coal Seams

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

6

Horizontal Well Length, 100 ft increments

Horizontal Well Drainage Area

= vertical drainage area

Pro

du

ctio

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

7

Vertical Well

Horizontal Well

8

Austin Chalk

Bryan

Houston

San Antonio

Pearsall Field

Austin Chalk Fields

AustinGiddings

Horizontal Drilling Sites

9

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.

10

Horizontal Drilling

Oil-filled fractures

11

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)

12

ROSPO MARE, ITALY

Water

Horizontal Well

Vertical Well

Slant Well

Oil

Pro

du

ctio

n,

m3 /D

70m

1982 1984 1986

250

500

13

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

14

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

15

NEW DRILLING TECHNOLOGY

Measurement While Drilling (MWD)

Directional Surveying and Control

Identification of Markers

Identify zones

16

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

17

Mud Motors

Drill without rotating pipe

Change hole direction while drilling without making a trip to change the BHA

Steerable systems

High-torque motors…

18

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.

19

POTENTIAL PROBLEMS IN HORIZONTAL DRILLING

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

Preventing/Remedying differential sticking

Excessive torque

20

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

21

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.

22

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 }

23

LONG-RADIUS WELLS

Used for achieving large horizontal displacements from platforms or drilling pads

Used for achieving very long horizontal sections (4000 ft +)

24

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

25

METHOD

Use conventional directional drilling technology

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

Or, use Navigation drilling systems with “steerable” drilling motors

26

MEDIUM - RADIUS WELLS

Build Rate: ~ 8-20 degrees/100 ft

Build Radius: ~ 300-700 ft

Length ofHorizontal Section:

~1,000-5,000 ft

27

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

28

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

29

SHORT - RADIUS WELLS

Build Rate: ~ 1-3 degrees/ ft

Build Radius: ~ 20-40 ft

Length of HorizontalSection:

400-1000 ft

30

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

31

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

32

Drill Pipe (rotating)

Clutch Sub (rotating)

Curved Drill Guide (non-rotating)

Clutch

Stabilizer

Stabilizer

Bit Sub (rotating)

Fig. 4: Short Radius Curve Drilling Assembly

33

Has Finally Taken Root

Multi-LateralCompletion Systemsfrom Baker Oil Tools

34

Multi-Lateral Drilling and Completions

Some Things are Designed for Easy Re-entry.

35

36

37

38

39

40

41

42

43

44

45

46

“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

47

48

49

50

51

52

53

54

End of Lesson 20

AATTMM