Page 196 - Intelligent Digital Oil And Gas Fields

152 Intelligent Digital Oil and Gas Fields

126
Old set point 125 psi
Set point
124 Proportional response
Time delay in response Integral response
122 On/Off
Derivative response
Pressure intake, psi 118
120

116
New set point 115 psi
114
112
110
1 23 4 5 6789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Count or Time
Fig. 5.2 Chart comparing the performance of a valve being operated in four different
control modes—proportional, integral, on/off, and derivative—to adjust pressure from
125 to 115psi, versus response time.

• Proportional (P): the valves and controller are adjusted in different grades
based on the change in the measured value from the set point. For exam-
ple, if a piece of equipment reaches a certain set point, a controller could
close a valve by 25%.
• Integral (I): operates at a rate proportional to the magnitude of the input
steps.
• Derivative (D): delivers proportional increase or decrease of a variable set
as a function of time. Rate action is a function of the change speed.
• Combinations: the best option for oil industry processes and DOF sys-
tems. Generally, a combination of P and I is the best option, because
integral allows rapid changes on slope and proportional reduces the off-
sets. Fig. 5.2 shows a pressure change versus time in response to different
control modes.

5.2 PREPARATION OF AUTOMATED
WORKFLOWS FOR E&P

Many exploration and production workflows require engineers to
coordinate data flows between several different applications. Studies have
shown (Al-Jasmi et al., 2013a,b,c) that engineers spend between 50% and
70% of their time gathering, formatting, and translating data to be used