Ut'!JYJRS lT l
TEKNOLOGI
PETRONAS
COURSE
PCB 4013/ PDB 4013- GAS FIELD ENGINEERING
DATE
28 AUGUST 2018 (TUESDAY)
TIME
09.00 AM - 12.00 NOON (3 HOURS)
INSTRUCTIONS TO CANDIDATES
1.
Answer ALL questions in the Answer Booklet.
2.
Begin EACH answer on a new page in the Answer Booklet.
3.
Indicate clearly answers that are cancelled, if any.
4.
Where applicable, show clearly steps taken in arriving at the solutions and
indicate ALL assumptions, if any.
5.
DO NOT open this Question Booklet until instructed.
6.
ATTACH Appendix 4 in Answer Booklet.
Note
i.
There are FOURTEEN (14) pages in this Question Booklet including the
cover page and appendices.
11.
DOUBLE-SIDED Question Booklet.
iii.
Graph paper(s) will be provided.
Universiti Teknologi PETRONAS
PCB4013/PDB4013
1.
a.
i.
State FIVE (5) different properties that are considered for the
calculation of bottom hole flowing pressure (BHFP) as compared to
bottom hole static pressure calculation (BHSP).
[5 marks]
ii.
Construct the friction factor equation for laminar flow, transitional flow,
and turbulent flow using the FIVE (5) properties from Q1 a(i). Indicate
the Reynold's number for each flow regime.
[6 marks]
b.
Well data is listed in TABLE Q1. Evaluate the BHFP using the Average
Temperature and Average z-Factor method with TWO (2) iterations for the
deviated well which is drilled to an inclination of 10°. Use APPENDIX 1-3 to
answer the question.
TABLE Q1: Well Data
Properties
Values
Specific gravity of gas
0.62
Gas pseudocritical pressure
667.8 psia
Gas pseudocritical temperature
343.37 °R
Gas flowrate
5,125 Mscfd
Flowing tubing-head pressure
1,125 psia
Flowing tubing-head temperature
100°F
Flowing bottom-hole temperature
298.5°F
Total Vertical Depth (TVD)
12,122 ft
Tubing ID
2.441 inch
[15 marks]
2
PCB4013/PDB4013
2<
a
A Well shows poor performance based on the bottom hole flowing pressure
results (BHFP). A well deliverability test is conducted to confirm the poor
performance. The collected data is listed in TABLE Q2. Evaluate the
Absolute Open Flow (AOF). Use APPENDIX 4 and attach it to the answer
booklet.
TABLE Q2: Well Data
Time
Pressure
q (MMscfd)
Remarks
(hours)
(psi a)
14
2345
0
Initial Shut-In
10
2170
3.8
Flow 1
10
2335
0
Shut-In
10
2050
5.5
Flow 2
10
2250
0
Shut-In
10
1750
7
Flow3
10
2245
0
Shut-In
10
1010
15
Flow4
26
990
9
Extended Flow
70
2345
0
Final Shut-In
[15 marks]
b
Differentiate THREE (3) properties that are required to determine gas well
deliverability test appropriate for a particular well. Select an equation and a
field measurement to determine these THREE (3) properties.
[9 marks]
3
PCB4013/PDB4013
3.
a.
Field Development Plan FOP study for reservoir A in the process of
finalizing the Gas Initially In Place (GIIP). The reservoir parameters are
summarized in TABLE Q3a and the reservoir top map is given in FIGURE
Q3a.
TABLE Q3a: Reservoir A properties.
Parameter
Reservoir pressure
Value
2,700 psia
Reservoir temperature
250°F
Average porosity
21%
Average water saturation
14%
Average thickness
7.3 ft
FIGURE Q3(a) : Reservoir A top map.
Estimate the GIIP, expressed in BSCF unit, for Reservoir A using the
approriate equation in APPENDIX 1 and the information in APPENDIX 5.
[5 marks]
4
PCB4013/PDB4013
b.
During development of Reservoir A, Well A and Well B were drilled at
Eastern Lobe and Western Lobe respectively. The first gas from the field
was on 1 January 2015. Reservoir pressure measurements were taken on
yearly basis at the end of the year. The production history and the reservoir
pressure are given in TABLE Q3b(i) and TABLE Q3b(ii) below.
FIGURE Q3b : Well A and well B locations.
TABLE Q3b(i): Well A production history
Year
Average Yearly
Pressure,
Gas rate MMscfd
psi a
1/1/2015
2,700
1/1/2016
90
2,332
1/1/2017
90
1,978
1/1/2018
90
1,631
1/7/2018
90
1,456
5
PCB4013/PDB4013
TABLE Q3b(ii): Well B production history.
Year
Average Yearly
Pressure,
Gas rate MMscfd
psi a
2,700
1/1/2015
i.
1/1/2016
79
2,004
1/1/2017
68
1,428
1/1/2018
60
916
1/7/2018
60
652
Estimate the total GIIP based on the production history of both wells
given in TABLE Q3b(i) and TABLE Q3b(ii).
[18 marks]
ii
Based on your answer in Q3b(i), evaluate the reservoir connectivity
between Eastern Lobe and Western Lobe. Justify your answer.
[2 marks]
6
PCB4013/PDB4013
4.
a.
Gas Sales Agreement (GSA) is needed before the gas field development
project begins. Explain why this agreement is important and provide FOUR
(4) examples of its components which impact the development decision in
FOP.
[5 marks]
b.
Well B nodal plot showing multiple plots at various reservoir pressures and
tubing sizes is given in FIGURE Q4b.
1000
I 3.s"
~-.N
900
,,
800
700
(II
'Vi
600
c..
QJ.
....
:::l
VI
VI
QJ
,_
CL.
500
,,
,,
......
~ .....
"
~ ... ~ ...~
li!'
'.
~-•llo..
~
~
400 ~
......
300
..
"·
.._
..
..:.¥.
... ~
.......
...,.
1'!11. , .
....
·.:,:_
,... ,'
"""~
~
', ...,
'
.•
•
••
40
D
60
""
. ····· ...
~
7
~
7"~
""" "
''
'-
I 4.5" I
.... ····· ...
.. .,
''"
••
•
•••
20
~
....>~
•••
100
,. .L
-- ,, - - - .......
.. ~ .... ... ·" ~~-··
••
""
,..,..;""
"..... """''
'--.
200
0
...
...............
,,
c
"
'· ' ...
80
[\..
"'
~\.
100
B
'
~
120
Gas Flowrate, MMScfd
"
A
FIGURE Q4b: Nodal Plot for Well Bas of 1/7/2018
Using the information from FIGURE Q4b and TABLE Q3b(ii), identify tubing
size of Well B. Justify your answer by comparing the performance of other
tubing sizes.
[4 marks]
7
PCB4013/PDB4013
c.
By referring to your answer in Q4b, describe the definition of the following
parameters and assess the plot to identify its value if any. You may indicate
your answer using sketch in the Answer Sheet.
i.
Absolute Open Flow
ii. Drawdown
iii. Reservoir pressure
iv. Stable solution or operating point
v. Unstable solution
vi. Erosional region
[12 marks]
d
As of 1/7/2018, by referring TABLE Q3b(ii), Well B is currently producing at
60 MMscfd. FIGURE Q4d shows gas production at different Water Gas
Ratios (WGR) and WHP.
Water Gas Ratio (STBIMMsd)
FIGURE Q4d : Sensitivity plot for Well B at various WHP and WGR.
i.
Identify Well B current operating point from FIGURE Q4d and the
WGR.
[2 marks]
8
PCB4013/PDB4013
ii.
Calculate the new produced water flowrate from Well B if WGR
increases by 100% from current WGR and WHP decreases to 100
psigo
[2 marks]
-END OF PAPER-
9
PCB4013/PDB4013
APPENDIX 1
List of formula and conversion unit
Ptt ) (Leos(})
Pwt = Ptt + 0.25 ( 100 lOO
f
= 4 2.28 - 4log
r
(
0.0023
d
21.25)1-
2
+ NRe 0 .9
0.0375y Lcos(}
s = - - - -9= - fl'
Pwf 2 -_ Ptt 2 e s
+ 6.67x1od5
4
q
2
B
fT 2 z2
cos (}
(
e s - 1)
1
GllP = 43,560Ah0(1- Swi)GI/P
B9i
=SCF
A= Acres
h=ft
T(Rankine)
= T(°F) + 460
1 kilometer square= 247 Acres
10
PCB4013/PDB4013
APPENDIX 2
Pseudo Reduced Pressure, Pr
3
1.1
4
~~=:.ti:.::..:J..:C::;;;I~~;;.r-:-,::".
6
1.1
1.0
0.9
0"8
N
..:
0.7
1.6
0.6
1.5
0
t5
ro
u.
:=:>-
:0
'iii
C/}
~
)
0.5
''
1.4
a.
E
0
0
0.4
1.3
0.3
1.2
0.25
1.1
Compressibility of
Natural Gases
(Jan. 1, 1941)
1.0
1.0
: j
:
. ''
~I
f.
0.9
0.9
7
8
9
11
10
12
13
Pseudo Reduced Pressure, Pr
11
14
15
PCB4013/PDB4013
APPENDIX 3
CIA$
If
,JI
'"
l't ,
liftAYITY
(Alii •
,.
1.-1
u
...
II
!i
~~
rt
U11
~
'•
s
!;
~
8.010
F«o.on
0.407
A0.001
~~
II..
•z
t
II~~ ' . .,
;!
IS
·0
tOt.
...
20
..:
•
ill
IIDL
~
loW:fll
;
·,;.
io
MOC..ECIJUR WI!IGHT, M
~ 3~~~~~~~~~~ ·--~--~-+--~--+--4--4
•
k
!!
.t
I 21---+---+~--fll.,.---~
,LCt±:E;§S~--LJ
o..&
2.8
\.0
.Coz
y
.,.
U
1,4
Pls.l.ll Vilcolity ratio
t.8
1.1
2.0
2.2
2.•
Ptluclcnductd ~
VCIS\JS pswdoAMliK"Cd
12
"
~
~
·'-'
:...".iu
,,...
I•
lfl
I,
~
I -.,;.:
.1011
co
II- II
I
I
I··*
~~
Its
1,1
U
l.O
U
tempattute. (After Carr ct al.)
3.4
PCB4013/PDB4013
APPENDIX 4
EXAM ID:
-----
TABLE NUMBER: - - DATE:
-----< ·-·-·-
----···~·---~----·-·--
------
---~-~-,
t
I
I
·-
13
I
I
Z Factor
:....
c
......
.tlo.
.j..l
':;
'ii
u.
N
0. 92 ~0.91
0.9
~.
~
0.88
0.87
.86
0.85·-0.84·-0.83
0.82
0.81
0.8
0
1J
200
400
600
800
()
1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000
Pressure
(psig)
Ill
)>
""C
""C
m
.tlo.
0
......
w
...._
1J
z
c
Ill
(II
w
><
0
.tlo.
0
......