Drilling Exam

8/9/2019 Drilling Exam

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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 whenit has completed its run? Discuss these performance criteria andsuggest which you would recommend as the most meaningful?

[4]

A2(a) Discuss the criteria and considerations which are used to determine the

mudweight required for drilling a well.[4]

(b) Describe how the minimum and maximum mudweight could bequantified.

[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 theseindicators and in particular if there could be any reason for the event,other than an influx, had taken place.

[8]

A4(a) What are the advantages and disadvantages of oil based mud as

opposed to water based mud?[4]

(b) Describe the way in which two properties of drilling mud are tested?[4]


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A5(a) List and describe the steps involved in drilling a well from a floating

drilling vessel. Highlight the aspects of the operation particularlyconcerned with safety.

[5]

(b) List the major differences between a surface and subsea wellheadsystem

[3]

A6(a) List and describe the basic components of an MWD system.

[6]

(b) Describe three applications of an MWD system. [2]


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Section B

B7

(a) Calculate the burst and collapse loads on the 9 5/8" production casingstring detailed in the following data. Select a casing string from thoseavailable on the basis of this calculation. State and discuss allassumptions used during the design.

9 5/8” Casing : 0 - 7900 ftTop of Packer : 7200 ftFormation Fluid Density : 9.5 ppgExpected gas gradient : 0.115 psi/ft

Depth of Production Intervals (TVD) : 7350 - 7750 ftMax. expected pressure grad.in production intervals : 14 ppgPacker fluid density : 9 ppg

Design Factors(burst) : 1.1(collapse) : 1.1

Casing Available (See attachment 1 for Specifications):

9 5/8" 47 lb/ft L-80 VAM9 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]

(b) Describe the impact of tension on the collapse rating of casing[4]

(c) List and discuss the functions of a conventional wellhead system.Describe how each of these functions are accommodated.

[4]


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B8Whilst drilling the 8 1/2" hole section of a vertical well with amudweight of 12 ppg the driller detects a kick. The well is shut in andthe following information is gathered :

Surface Readings :

Shut in Drillpipe Pressure : 600 psiShut in Annulus Pressure : 750 psiPit Gain : 20 bbls

Hole / Drillstring Data :

Hole Size : 8 1/2 "Depth of kick : 8000 ft.

Previous Casing Shoe : 9 5/8", 53.5 lb/ftDepth 9 5/8" shoe : 6500 ft. TVDLOT at Previous shoe : 4875 psi (0.75 psi/ft Equivalent

Mudweight)

BHA :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

(a) Calculate and discuss the following :

i. The type of fluid that has entered the wellbore ?

ii. The mudweight required to kill the well.[10]

(b) Briefly describe the “one circulation method” of killing a well.

[8]

(c) What precautions would you take to ensure that an influx could becontrolled and killed if it occurred during drilling or during tripping?

[2]


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B9It 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 ftE 400 000 ft

Target Location : N 8 346 500 ftE 397 000 ft

Target Depth (TVD) : 8000 ft.Kickoff Point : 2500 ft.

Build up Rate : 2.50 per 100 ft.

(a) Calculate the following :

(i) the drift angle of the well.(ii) the TVD and horizontal deviation at the end of the build up

section.(iii) the total measured depth to the target.

[12]

(b) List and discuss the considerations when designing the wellpath of adeviated wellbore.?

[5]

(c) List and discuss the advantages and disadvantages of using agyroscope in place of a magnetic compass for measuring thedirection of the borehole trajectory

[3]


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B10The 13 3/8” intermediate casing string of a well is to be cemented inplace 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 ppgYield 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

(a) Calculate the following (See Attachment 2 for capacities):

i. The required number of sacks of cement for the 1st stage and2nd stage of the job (Allow 20% excess in open hole).

ii. The volume of mixwater required for each stage.iii. The displacement volume for each stage.

[12]

(b) Write a cementing programme for the above operation.

(Note : Include in this programme any procedures/precautions whichyou think will ensure a good cement job).[6]

(c) Suggest three reasons why a two stage cementing operation isconducted?

[2]

END OF PAPER


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Attachment 1

STRENGTH OF CASING

CASING BURSTSTRENGTH

(PSI)

COLLAPSESTRENGTH

(PSI)

9 5/8" 47 lb/ft L-80 VAM 6870 4750

9 5/8" 53.5 lb/ft L-80 VAM 7930 6620


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Drilling Exam

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