MÆRSK OLIE OG GAS AS – GYMNASIE OPGAVE - 2008
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2
OPGAVE – beregn olie mængden i et reservoir
The Geology Case – now it is your turn!
MY OWN LITTLE OILFIELD
THE MOLO FIELD
OPGAVE
3
OPGAVE – Baggrundsinformation 1
Gross Rock Volume is:
Volume of rock containing our reservoir
STOIIP (Stock Tank Oil Initially In Place) or
GIIP (Gas Initially In Place) is:
Amount of hydrocarbons present in our reservoir
RESERVES are:
Hydrocarbons we can produce (given present
conditions)
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OPGAVE – Baggrundsinformation 2
Recovery Factor is depending on:
• Reservoir Quality & Conditions
• Oil and Gas Type
• Number of Production Wells and Type
(Cost)
• Production Method (Enhanced Recovery)
RESERVES = [STOIIP] · [Recovery Factor]
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OPGAVE – Baggrundsinformation 3
YOUR FACTS:
1) We have 2 seismic profiles across the reservoir
2) The MOLO-1 well penetrated the top of the reservoir at a depth of
XXXX feet
3) An oil-water contact was found in MOLO-1 at a depth of XXXX feet
4) The average porosity (Φ) was found to be 0.XXX (XX.X vol.%)
5) The penetrated reservoir is reduced by interspaced non-reservoir
rock → N/G ratio of 0.90 (90 vol.%)
6) The average water saturation (Sw) is 0.XX (XX vol.%)
7) The Formation Volume Factor (FVF) is 1.2 (the reduction in oil
volume due to loss of gas content when moving from reservoir
pressure and temperature to surface conditions)
8) The Recovery Factor (RF) is estimated to be 0.25 (i.e. 25 % of the
STOIIP will be produced to surface).
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OPGAVE: My Own Little Oilfield 1
YOUR TASK:
1) Calculate the Gross Rock Volume (GRV)
2) Calculate Stock Tank Oil Initially In Place (STOIIP)
3) Calculate the Reserves
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OPGAVE: My Own Little Oilfield 2
MOLO-1 well
WEST
NORTH
EAST
SOUTH
Seismic Profiles
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OPGAVE: My Own Little Oilfield 3
NOTE – feet!
MOLO-1 well
feet
5700
Top of
Reservoir
6000
6300
6600
6900
7200
7500
Oil-Water
Contact /
Transition
Zone
7800
1000
NOTE – meter!
OPGAVE:
0
7700
GR
api
150 0.2
LLD
OHMM
200 0.6
TNPH
CFCF
0
TVDSS
FT
6700 0.2
LLS
OHMM
200 0.75
DRHO
G/C3
-0.25
0.2
MSFL
OHMM
200 1.7
RHOB
G/C3
140
DTCO1
US/F
My Own
DEPTH
FT
0.5
PHICFCF
0 1
BVW
0.5
2.7
40
MOLO-1
0
SWCFCF
0 0
VSH
CFCF
1
1
PHICFCF
0
TVDSS
FT
Little Oilfield 4
0.5
VGASCFCF
0
0
0.5
VOILCFCF
0
VSH
VSH
ListaPHIFm
North Sea Marl
Top D1
6800
GOC
A wireline log
showing the
porosity and
hydrocarbon
saturation
profile from the
well
6950
Top D2A
Top D2B
7000
Mh
M1A
6900
7050
M1b1
M1b2
M1b3
M1b4
M1b5
M1b7
Approximately 180 ft
of chalk oil-reservoir
7100
7000
h  60 meters
M1b8
7150
M2
7200
7100
7250
M3
7300
OWC
M4
7350
7200
OPGAVE: My Own Little Oilfield 5
Apply a known geometrical shape to
the reservoir shape: The Spherical Cap
h
α
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OPGAVE: My Own Little Oilfield 6
Gross Rock Volume is then
the volume of a spherical cap
with a height of h and a
radius of α
α
h
h is estimated using the log
from the well –
You then find α from the
seismic profiles
0
Calculate GRV from this
expression (expect a large
number!):
GRV = 1/6·π·h·(3·α²+h²)
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OPGAVE: My Own Little Oilfield 7
• Gross Rock Volume (GRV)
• Net to Gross (N/G)
• Porosity (Φ)
• Oil Saturation (Soil equal to 1 minus Water Saturation Sw)
• Oil Formation Volume Factor (FVF given as a value of 2)
Calculate STOIIP using this expression
(the unit at this stage is m3):
STOIIP = GRV ∙ N/G ∙ Φ ∙ Soil / FVF
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OPGAVE: My Own Little Oilfield 8
We now re-calculate STOIIP in m3 to STOIIP in million bbls
using this expression:
STOIIPmillion bbls= STOIIPm3 ∙ 6.29 / 1,000,000
Finally the reserves are calculated given a recovery
factor of 0.25 (25%):
Reserves = STOIIPmillion bbls ∙ RF
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OPGAVE: My Own Little Oilfield 9 – Excel regneark til beregning
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The End
MÆRSK OLIE OG GAS AS
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