l16 - field data
DESCRIPTION
Phase behaviorby Prof. Maria BarrufetTRANSCRIPT
PETE 310
Lecture # 16
Chapter 9 – Properties of Black
Oils from Field Data
Analyzing Production Trends
Gas production trends
– Dissolved gas only
– Dissolved and free gas
Pressure trends
– Bubble point pressure determination
– Adjustment of surface gas data
Separators
)STB/scf( GOR and
y iST
)STB/scf( GOR and
y iSP
iSTx
Wellhead
Usually vented
Note for a black oil have more liquid produced than for a wet gas –
Less oil shrinkage and lower GOR
Production Trends
Production Data - Aggie Field
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 1000 2000 3000 4000 5000 6000
Cumulative Oil Production (MSTB)
Pro
du
cin
g G
as
Oil R
ati
o (
sc
f/S
TB
)
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
Pre
ss
ure
(p
sia
)
GOR (scf/STB)
Average Production Pressure
(psia)
Production Trends
Production Data - Aggie Field
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 1000 2000 3000 4000 5000 6000
Cumulative Oil Production (MSTB)
Pro
du
cin
g G
as
Oil R
ati
o (
sc
f/S
TB
)
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
Pre
ss
ure
(p
sia
)
GOR (scf/STB)
Average Production Pressure
(psia)
pb
RSB
Adjustment of Surface Gas Data
Gas from the stock tank usually is vented
Ignoring this gas could lead to estimates for Rsb 10% to 20% lower
Solution:
– Add stock-tank gas-oil ratio obtained from a correlation to the Rsb obtained from field data
Graphical Procedure
Interpolations
needed
Easy to mix up
lines
Note the trends in
RST
395scf/STB
Adjustment of Surface Gas Data
Reading from graph can lead to
substantial round off error
Equation B-36 in Appendix B page
518 has been used to create Figure
9.3
Be careful with the units required in
the equation
Adjustment of Surface Gas Data
Equation
Here the temperature is in oF
Read constants A1 through A5 from text book
Note the differences in oil and gas specific gravities (density oil/density water, vs Gas molecular weight/ air molecular weight)
Note subscripts STO at stock tank p and T, SP at separator p and T
SP5SP4gST3STO21ST TlogAplogAlogAlogAARlog
A Conceptual quiz
An oil with API gravity
of 50 will have a lower
RST than an oil with
API gravity of 20
– TRUE ?
– FALSE?
– DEPENDS?
Discuss
395scf/STB