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# Drilling Engineering Exam Papers

```HERIOT-WATT UNIVERSITY
DEPARTMENT OF PETROLEUM ENGINEERING
Examination for the Degree of MEng in Petroleum Engineering
Drilling Engineering
```

Section A

## A1

(a) List the principle features of a roller cone drillbit and state how the drilling conditions would affect the design of these features.

[4]

(a) What are the criteria used to assess the performance of a drillbit when it has completed its run? Discuss these performance criteria and suggest which you would recommend as the most meaningful?

[4]

## A2

• Discuss the criteria and considerations which are used to determine the mudweight required for drilling a well.

[4]

• Describe how the minimum and maximum mudweight could be quantified.

[4]

## A3

(a) List and describe four of the principle indicators that an influx had occurred whilst drilling ahead? Highlight the value of each of these indicators and in particular if there could be any reason for the event, other than an influx, had taken place.

[8]

## A4

• What are the advantages and disadvantages of oil based mud as opposed to water based mud?

[4]

• Describe the way in which two properties of drilling mud are tested?

[4]

## A5

• List and describe the steps involved in drilling a well from a floating drilling vessel. Highlight the aspects of the operation particularly concerned with safety.

[5]

• List the major differences between a surface and subsea wellhead system

[3]

## A6

• List and describe the basic components of an MWD system.

[6]

• Describe three applications of an MWD system. [2]

Section B

## B7

• Calculate the burst and collapse loads on the 9 5/8" production casing string detailed in the following data. Select a casing string from those available on the basis of this calculation. State and discuss all assumptions used during the design.
 9 5/8” Casing : 0 - 7900 ft Top of Packer : 7200 ft Formation Fluid Density : 9.5 ppg Expected gas gradient : 0.115 psi/ft Depth of Production Intervals (TVD) Max. expected pressure grad. : 7350 - 7750 ft in production intervals : 14 ppg Packer fluid density Design Factors : 9 ppg (burst) : 1.1 (collapse) : 1.1

Casing Available (See attachment 1 for Specifications):

9 5/8" 47 lb/ft L-80 VAM

9 5/8" 53.5 lb/ft L-80 VAM

Note :

1. Gaslift may be used at a later stage in the life of this well.

[12]

• Describe the impact of tension on the collapse rating of casing

[4]

• List and discuss the functions of a conventional wellhead system.

Describe how each of these functions are accommodated.

[4]

Whilst drilling the 8 1/2" hole section of a vertical well with a mudweight of 12 ppg the driller detects a kick. The well is shut in and the following information is gathered :

 Shut in Drillpipe Pressure: 600 psi Shut in Annulus Pressure : 750 psi Pit Gain Hole / Drillstring Data : : 20 bbls Hole Size : 8 1/2 " Depth of kick : 8000 ft. Previous Casing Shoe : 9 5/8", 53.5 lb/ft Depth 9 5/8" shoe : 6500 ft. TVD LOT at Previous shoe BHA : : 4875 psi (0.75 psi/ft Equivalent Mudweight) Bit : 8 1/2" Drillcollars : 300 ft of 6.25" x 2 13/16" Drillpipe : 5", 19.5 lb/ft

See attachment 2 for annular capacities

• Calculate and discuss the following :
1. The type of fluid that has entered the wellbore ?
2. The mudweight required to kill the well.

[10]

• Briefly describe the “one circulation method” of killing a well.

[8]

• What precautions would you take to ensure that an influx could be controlled and killed if it occurred during drilling or during tripping?

[2]

It has been decided to drill a well with a Type 1 (build and hold) profile. The well will be drilled to the following specifications:

Geographical Locations based on local grid :

Rig Location : N 8 350 000 ft

E 400 000 ft

Target Location : N 8 346 500 ft

E 397 000 ft

Target Depth (TVD) : 8000 ft.

Kickoff Point : 2500 ft.

Build up Rate : 2.50 per 100 ft.

• Calculate the following :
• the drift angle of the well.
• the TVD and horizontal deviation at the end of the build up section.
• the total measured depth to the target.

[12]

• List and discuss the considerations when designing the wellpath of a deviated wellbore.?

[5]

gyroscope in place of a magnetic compass for measuring the

direction of the borehole trajectory

[3]

The 13 3/8” intermediate casing string of a well is to be cemented in place with a two stage cement job. The details of the job are as follows

:

Previous Casing Shoe (20") : 1800 ft.

13 3/8" 72 lb/ft Casing Setting Depth : 5100 ft.

17 1/2" open hole Depth

(Calipered @ 18" average) : 5110 ft. Multi-Stage Collar Depth : 1750 ft.

Shoetrack : 60 ft.

Cement stage 1 (5100-3300 ft.)

Class 'G' + 0.2% D13R (retarder) : 15.8 ppg

Yield of Class 'G' + 0.2% D13R : 1.15 ft3/sk

Mixwater Requirements : 0.67 ft3/sk

Cement stage 2 (1750-1250 ft.)

Class 'G' + 8% bentonite + 0.1% D13R : 13.2 ppg

Yield of Class 'G' + 8% bentonite + 0.1% D13R : 1.89 ft3/sk

Mixwater Requirements : 1.37 ft3/sk

• Calculate the following (See Attachment 2 for capacities):
1. The required number of sacks of cement for the 1st stage and 2nd stage of the job (Allow 20% excess in open hole).
2. The volume of mixwater required for each stage.
• The displacement volume for each stage.

[12]

• Write a cementing programme for the above operation.

(Note : Include in this programme any procedures/precautions which you think will ensure a good cement job).

[6]

• Suggest three reasons why a two stage cementing operation isconducted?

[2]

END OF PAPER

Attachment 1

STRENGTH OF CASING

 CASING BURST STRENGTH (PSI) COLLAPSE STRENGTH (PSI) 9 5/8" 47 lb/ft L-80 VAM 6870 4750 9 5/8" 53.5 lb/ft L-80 VAM 7930 6620

Attachment 2

VOLUMETRIC CAPACITIES

 Casing bbls/ft ft3/ft 13 3/8” 72 lb/ft Casing: Open Hole 0.1480 0.8314 18" Hole Annular Spaces 0.3147 1.7671 20” Casing x 13 3/8" Casing 0.1815 1.0190 18” Hole x 13 3/8” Casing 0.1410 0.7914 8 1/2” hole x 6 1/4” drillcollars 0.0323 0.1895 8 1/2” hole x 5" drillpipe 0.045 0.258
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