volumetric reserves estimates

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

volumetric reserves estimates

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