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8/12/2019 Volumetric Reserves Estimates
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Volumetric ReservesEstimates
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Instructional Objectives
You will be able to
Calculate volume of oil- and gas-in-
place
Calculate initial oil and gas reserves
Calculate the remaining reserves
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What are Reserves?
Oil and gas trapped beneath the earths
surface that can be recovered under
existing economic conditions and with
current technology.
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Reserves Uncertainty
Cumulative
Production
True Ultimate
Recovery
Wells
Completed
TimeAbandonment At
Economic Limit
Increasing
Recovery
Range ofRecovery Estimates
III III
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Volumetric Estimate of
Oil Reserves
Original oil in place (OOIP)
Original oil reserves = Npa= N x ER
Original solution gas in place = N x Rsi
oiwi B/)S1(Ah7758N
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Inputs to Volumetric ReservesGRC
0 150SPCMV-160 40
ACAL6 16
ILDC0.2 200
SNC0.2 200
MLLCF0.2 200
RHOC1.95 2.95
CNLLC0.45 -0.15
DTus/f150 50
001) BONANZA 1
10700
10800
10900
h
Calculate , Sw
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Reservoir Area and Volume
Oil Producing Well
Water Water
Oil Zone
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Net Oil Pay Isopach Map
0
Well #2
45
Well #1
21
Well #5
64
Well #355
Well #4
49
Dry Hole #1
0
Dry Hole #2
2
20
40
50
60
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Determination of Reservoir
Bulk Volume
Ah = Reservoir Bulk Volume
A = area for the reservoir, lease,unit, or an individual wells
drainage area
h = net hydrocarbon thickness
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Calculating Reservoir
Bulk Volume Computer Mapping Programs
Traditional Methods
Trapezoidal Rule
Pyramidal Rule
navgnnb AhAAAAhV )2...2(5.0 11 2
11
3nnnnbb AAAA
hVV
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Exercise 1
Calculate original oil In place and oil
reserves for an oil reservoir withouteither a gas-cap or water influx
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Exercise 1
Calculate original oil In place and oil
reserves for an oil reservoir withouteither a gas-cap
or water influx
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Exercise 1Solution
Ah = 119,250 acre-ft
OOIP = 148,177,000 STB
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Exercise 1Solution
Reserves = 20.74 MMstb
Solution gas in place = 66.7 Bscf
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Exercise 1Solution
OOIP = 904,600 STB
Remaining Reserves = 8.74
MMstb
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Volumetric Estimate of
Gas Reserves
Original gas in place (OGIP)
Original gas reserves = OGIP x R.F.
giwi B/)S1(Ah7758OGIP
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Oil Reservoir With a Gas Cap
Oil Producing Wells
OilZone Gas Cap
OilZone
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Volumetric Dry Gas Reservoirs
Gas Zone
Water
SealingFault
A. Cross Section
B. Map View
FaultFault
Gas
Reservoir
0 2040
60
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Dry Gas Reservoirs With
Water Influx
Water Water
Gas Zone
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Recovery Factors for Gas
Reservoirs Analogy
Volumetric dry gas reservoirs
Gas reservoir with water influx
v
v
gi
gr
ga
giv
E
E1
S
S
B
BE1.F.R
ga
gi
B
B1.F.R
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Exercise 2
Calculate original gas In place,
gas recovery factor and gasreserves in a volumetric dry gas
reservoir
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Solution
Exercise 2
G = 10.5 Bscf
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Exercise 2
Solution
R.F. = 53.1%
Gp = 5.58 Bscf
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Exercise 3
Calculate total original gas in
place and oil reserves for an oilreservoir with a gas cap
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Exercise 3
Solution
OOIP = 130,334,000 STB
Original solution gas-in-place = 78.2 Bscf
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Solution
Exercise 3
OGIP = 22.1 Bscf (gas-cap)
Total OGIP = 100.3 Bscf
Oil reserves = 45,617,000 STB
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Exercise 3
Solution
Calculate total original gas inplace and oil reserves for an oil
reservoir with a gas cap
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Exercise 4
Calculate gas reserves and
recovery factor for a gasreservoir with water influx
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Exercise 4
SolutionGp = 8.2 Bscf
R.F. = 78.1%
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Exercise 4
Solution
R.F. = 68.1%
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Nomenclature
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Nomenclature
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References
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Summary
OOIP = 7758 Ah (1 - Swi)/Boi
Oil reserves = OOIP x R.F.
OGIP = 7758 Ah (1 - Swi)/Bgi
Gas reserves = OGIP x R.F.
Remaining reserves = Reserves at
original conditions - cumulative
production