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Drilling Engineering Tutorials

Drilling Tutorials 2011

Ex. 1 Leakoff Test

After having conducted a Leak off test at the 13 3/8" casing shoe of a vertical well the following data is reported :

TVD of 13 3/8" Shoe : 5200 ft. Mudweight in hole : 10.0 ppg

Vol. pumped

bbls

Surface Pressure

psi

0.5

100

1.0

240

1.5

370

2.0

500

2.5

630

3.0

750

3.5

860

4.0

995

4.5

1060

4.75

1090

  1. What is the maximum allowable static mudweight in the next (12 1/4") hole section?
  1. Assuming that the circulating pressure losses in the annulus will be 200psi, what is the maximum allowable mudweight, (allowing for ECD) in the next (12 1/4") hole section?
  1. What would be the MAASP in the next hole section, if the mudweight in the next hole section was increased to 11.0 ppg ?

(State clearly any assumptions in your answer) (6)

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Drilling Tutorials 2011

Ex. 2 Well Control

Whilst drilling the 12 1/4" hole section of a vertical well with a mudweight of 10.5 ppg the driller detects a kick. The well is shut in and the following information is gathered

Surface Readings :

Shut in Drillpipe Pressure : 700 psi Shut in Annulus Pressure : 900 psi Pit Gain : 33 bbls

Hole / Drillstring Data :

Hole Size : 12 1/4 "

Depth of kick : 7250 ft. TVD Previous Casing Shoe : 13 3/8", 53.5 lb/ft Depth 13 3/8" shoe : 3800 ft. TVD

LOT at Previous shoe : 3230 psi (0.85 psi/ft Equivalent Mudweight)

BHA : Bit : 12 1/4"

Drillcollars : 400 ft of 9" x 2 13/16"

Drillpipe : 5", 19.5 lb/ft

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

(8)

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VOLUMETRIC CAPACITIES

Drillpipe

bbls/ft

ft3/ft

5" drillpipe :

0.01776

0.0997

Casing

13 3/8" 72 lb/ft Casing:

0.1480

0.8314

Open Hole

13" Hole

0.1642

0.9220

18" Hole

0.3147

1.7671

Annular Spaces

   

12 ¼" hole x 5" drillpipe

0.1215

0.6822

12 ¼" hole x 9" drillcollars:

0.0671

0.3767

13” Hole x 9 5/8" Casing

0.0742

0.4166

18" hole x 13 3/8" Casing:

0.1410

0.7914

20" Casing x 13 3/8" Casing:

0.1815

1.0194

8 1/2" hole x 5" drillpipe:

0.0459

0.2577

8 1/2" hole x 6 1/4" drillcollars:

0.0330

0.1926

Drilling Tutorials 2011

Ex. 3 Intermediate Casing Design

You are required to calculate the burst and collapse loads on the 13 3/8” intermediate casing for a gas development well on the basis of the following data :

Casing Size :

Setting Depth :

Formation Fluid Density :

 

13 3/8"

6600 ft

9.5 ppg

Mud weight in which the casing is to be run : Depth of next (12 1/4”) hole section : Expected Pore Pressure Gradient at

 

11.5 ppg 8300 ft

bottom of 12 1/4” hole:

 

12.5 ppg

Expected Frac. Pressure Gradient at the 13 3/8” shoe Expected gas gradient :

 

0.85 psi/ft.

0.115 psi/ft

Design Factors : (Burst)

1.1

 

(Collapse)

1.0

 
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Drilling Tutorials 2011

Ex. 4 Production Casing Design

You are required to calculate the burst and collapse loads on the 9 5/8" production casing string for a gas development well on the basis of the following data :

Setting Depth of 9 5/8" Casing :

Top of Production Packer :

Formation Fluid Density :

Expected gas gradient :

10100 ft

9550 ft

9 ppg

0.115 psi/ft

Depth of Production Interval (TVD) :

9680 - 9950 ft

Maximum expected pressure at top of Perforations :

5100 psi

Packer fluid density :

9 ppg

Design Factors (burst) :

1.1

(Collapse) :

1.0

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Drilling Tutorials 2006

Ex.6 - Cementing

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") :

1500 ft.

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

4300 ft.

17 1/2" open hole Depth (Calipered @ 18" average) :

4330 ft.

Multi-Stage Collar Depth :

1450 ft.

Shoetrack :

60 ft.

Mud Density When cement job starts :

12 ppg

Cement stage 1 (4300-2800 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 (1450-950 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

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

(12)

VOLUMETRIC CAPACITIES

Drillpipe

bbls/ft

ft3/ft

5" drillpipe :

0.01776

0.0997

Casing

13 3/8" 72 lb/ft Casing:

0.1480

0.8314

Open Hole

13" Hole

0.1642

0.9220

18" Hole

0.3147

1.7671

Annular Spaces

   

12 ¼" hole x 5" drillpipe

0.1215

0.6822

12 ¼" hole x 9" drillcollars:

0.0671

0.3767

13” Hole x 9 5/8" Casing

0.0742

0.4166

18" hole x 13 3/8" Casing:

0.1410

0.7914

20" Casing x 13 3/8" Casing:

0.1815

1.0194

8 1/2" hole x 5" drillpipe:

0.0459

0.2577

8 1/2" hole x 6 1/4" drillcollars:

0.0330

0.1926

Solution - Cementing Tutorial

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Drilling Tutorials 2011

Ex. 5 Directional Well Planning

Using the following data, design a deviated well using a build and hold trajectory.

TVD Target 9700 ft

Horizontal Departure of Target 2400 ft

KOP 1500 ft

BUR 2 degrees/100 ft

Determine the following :

  • Tangent
  • Along Hole Depth at the end of the Build up Section
  • True Vertical Depth and Horizontal departure of End Build up Section
  • Along Hole Depth at
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Drilling Tutorials 2011

Ex. 6 - Directional Surveying

Whilst drilling a deviated well to a target at 9800 ft. TVD. The following data is recorded at station No. 37 (The target bearing is 60o)

STATION

MD

INC.

AZI.

N

E

TVD

VS

36

5300

27

55

175

254

4970

306

37

5400

28.5

57

       

Calculate the North and East co-ordinates, TVD and vertical section of station No. 37 using the average angle method.

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