1. Chapter 3 Casing design

2. Casing Design What is casing? Casing Cement Why run casing?
1. To prevent the hole from caving in
2. Onshore - to prevent contamination of fresh water sands
3. To prevent water migration to producing formation

3. Casing Design 4. To confine production to the wellbore
5. To control pressures during drilling
6. To provide an acceptable environment for subsurface equipment in producing wells
7. To enhance the probability of drilling to total depth (TD)
e.g., you need 14 ppg mud to control a lower zone, but an upper zone will fracture at 12 lb/gal.
What do you do?

4. Types of Strings of Casing
Diameter Example
16”-60” ”
16”-48” ”
8 5/8”-20” /8”
1. Drive pipe or structural pile
{Gulf Coast and offshore only} 150’-300’ below mudline.
2. Conductor string. 100’ - 1,600’
(BML)
3. Surface pipe. 2,000’ - 4,000’

5. Types of Strings of Casing
Diameter Example
4. Intermediate String
5. Production String (Csg.)
6. Liner(s)
7. Tubing String(s)
7 5/8”-13 3/8” /8”
4 1/2”-9 5/8” ”

6. Example Hole and String Sizes (in)
Hole Size
Pipe Size
36”
26”
17 1/2
12 1/4
8 3/4
Structural casing
Conductor string
Surface pipe
IntermediateString
Production Liner
30”
20”
13 3/8
9 5/8 7