Project Management in the Oil and Gas Industry

4.3.6 (S) 
Curve
The cost curve is called the (S) curve, whereas in all projects in the calcu-
lation of costs and distribution it to the Schedule, it takes the same form 
letter (S).
In the previous example, pouring concrete foundations is presented in 
the following figure: the first column represents the various activities and, 
on the other side, a Gantt chart was drawn and represents the cost of each 
item per day. For easy calculation assume that every activity cost is 1000 
dollars per day.
This is done through the compilation of costs in the bottom row. With 
the first of the two cases, the situation is that each activity starts and fin-
ishes early and, in the second case, they start and finish late.
When we assign the cumulative cost curve and establish the relationship 
between cost and time, we will get the (S) curve, as in the following figure. 
We find the first curve in the case of an early implementation of the activi-
ties and the second curve as all activities that have been implemented in 
the latest time.
From the previous figure, we find that the cost budget is presented by 
the envelope curve. When the cost is higher than planned it should be in 
shape to do the work well; this pre-schedule completion is called “ahead of 
schedule.”
Figure 4.2 Distribution of cost on the activity.
K$ Activity
3
1
2
3
4
5
6
7
8
10
9
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
–
–
–
–
–
–
–
1
2
3
5
7
9
11
13
17 15
19
21
22
23
24
25
26
27
28
29
30
31
32
33
34
1
2
3
4
5
6
7
8
10
9
11
12
13
14
16
18
20
22
24
26
28
30
32
33
34
Mobilization
8
Excavation
10 Pouring conc.
1
Mech. packg
1
Grouting
2
Comm & start up
4
Install piping
5
Connect piping
Sum
4
Install piping
5
Connect piping
Sum

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Project Management in the Oil and Gas Industry
Figure 4.3 Cash flow in case of early dates.
40
35
30
25
20
15
10
5
0
1 2 3 4 5 6 7 8 9 10 11 12 13