Wellbore Surveying

Survey Tools

Types of Tools

• Single shot– Magnetic– Gyro

• Multi shot– Magnetic– Gyro

• Steering tools– Magnetic– Gyro

• MWD– Magnetic– Gyro

Totco• Mechanical

• Gravitational• Paper output

• Disc needs 2 pin holes• Recoverable

• Trips• Wireline

Mechanical Inclination• Teledrift

(Anderdrift)• Inclination only+/- ½ degree accuracy

Single-shot• MSS– Mechanical– Film record– Timing– Exposure– Developing– Reading

Multi-shot• MMS– Mechanical– Strip film record– Timing on connections– Exposure– Developing– Reading

Steering Tool

Electronic Multi Shot

• The EMS instrument provides the same information as the magnetic multi-shot.

• It is using a system of magnetometers and accelerometers very similar to the one of the steering tool but is battery operated.

• The tool is programmed on surface, shots are taken are programmed time intervals and stored in memory, data are dumped from the memory and processed when the tool is back on surface after the run.

Gyro Surveying Tool

• Gyroscopic systems are not affected by magnetic interference. Mainly used to survey inside casings or to kick-off wells when magnetic interference is too high.

• Free Gyros (film based) and Rate Gyros (fully electronic) are the two main types of gyro systems.

• Gyro Principle– Balanced spinning mass, free to rotate on one or more axis– Is resistant to external forces and will tend to maintain his

heading throughout survey interval.– In a nutshell “a Gyro is lazy”.

Free Gyro Surveying Tool• Uses a similar photographic

instrument as the MSS or MMS.

• Powered by battery and run on slick line or wire line.

• Once accurately aligned to a reference point before use will maintain this heading throughout survey interval.

• Corrections for changes in heading can be applied later

Surface Recorded Gyro• A down-hole electronics package

replaces camera angle-unit and timer.• A wire line supplies power and connects

the probe with a surface computer that monitors probe performance and prints survey data as it is gathered.

• Accelerometers instead of Angle-Units are used to measure hole inclination.

• Problems with battery powered mechanical cameras are eliminated and survey data is supplied in real time.

• The surface computer can monitor probe performance, therefore time wasted by mis-runs is reduced.

Survey Tools• Totco• Single-shot• Multi-shot• Teledrift (Anderdrift)• Gyro MWD• EMS• Photo-mechanical Gyro• RIGS• North seeking rate gyro• SRG• GEMS

• Gyrodata(RGS)• GMS• Inertial Guidance

Systems(IGS)• Tuning Fork gyro• Magnetic Steering Tool• Optical

Survey CalculationFrequency

Pattern Drilling Practices

• The direction of the error is dependent on where the stationary surveys are taken relation to the slide/rotate sequences.

Pattern Drilling Practices

When stationary surveys are taken at the beginning of each slide sections, results in the maximum POSITIVE TVD error (shallow)

Pattern Drilling Practices

Pattern Drilling Practices

Pattern Drilling Practices

When stationary surveys are taken at the beginning of each rotate sections, results in the maximum NEGATIVE TVD error (Deeper)

Pattern Drilling Practices

Pattern Drilling Practices

Slide/Rotate Spacing

ActualSlide

Rotate

Calculated

Slide then RotateCalculation is deep

Slide/Rotate Spacing

Actual

Rotate then SlideCalculation is shallow

Calculated

Slide

Rotate

Slide/Rotate Spacing

Actual

Calculated

Rotate – Slide – Rotate Calculation is on Depth

Rotate

Rotate

Slide

Static vs. MCT Surveys

3500 4000 4500 5000 5500 6000 6500 7000 7500MD (ft)

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

90.0

Incl

inat

ion

(Deg

)

-9.0

-8.0

-7.0

-6.0

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

Delta

TVD

(ft)

Static vs MCT Inclination

DMAG Static InclMCT InclDelta TVD

Static vs. MCT TVD

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600Along Hole Departure (ft)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

TVD

(ft)

-9.0

-8.0

-7.0

-6.0

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

Delta

TVD

(ft)

Static vs MCT TVD

DMAG Static TVDMCT TVDDelta TVD

Static vs. MCT TVD

2150 2200 2250 2300 2350 2400 2450 2500 2550 2600 2650Along Hole Departure (ft)

2100

2150

2200

2250

2300

2350

2400

2450

2500

2550

2600

2650

2700

2750

TVD

(ft)

-9.80

-9.60

-9.40

-9.20

-9.00

-8.80

-8.60

-8.40

-8.20

-8.00

-7.80

-7.60

-7.40

-7.20

Delta

TVD

(ft)

Static vs MCT TVD

DMAG Static TVDMCT TVDDelta TVD

Practical• Build a horizontal well with a continuous build of

3deg/30m to 90 deg from 0m MD.• Record the TVD at TD.Then, Follow instructions from Instructor!!!• Survey Frequency Scenarios per 30m

Slide – Rotate – Slide Slide – Slide – Rotate Rotate – Slide – Slide Rotate – Rotate – Slide Slide – Rotate – Rotate Rotate – Slide – Rotate

End of Module