5

1

FLUIDSPresentation Agenda:

Composition of Hydrocarbon Fluids, Parameters and Measurements

Significance in Play/Prospect Evaluation

A Simplified Classification

2

FLUIDS Commercial hydrocarbon fluids comprise a series of compounds of

hydrogen and carbon from simple methane gas (CH4) through to complex heavy oils (C15+).

The conventional twofold division of produced commercial hydrocarbon products into oil and gas is an artificial one based on the hydrocarbon state at surface conditions.

There exists in the subsurface a continuum of complex fluids between the two end members. At atmospheric conditions, dissolved gas is liberated from the oil and liquids condense out from the gas due to the drop in temperature and pressure.

The hydrocarbon series can be divided up into constituent parts by the use of the gas oil ratio (GOR) also known as the Gas Liquid Ratio (GLR). This ratio is in volume per volume at subsurface conditions, expressed as standard cubic feet of gas per barrel of oil (scf/bbl) or cubic metres of gas per cubic metre of oil (m3/m3).

3

FLUIDS

GAS OILCOMPLEX FLUIDS

diphasicmonophasic

e.g. condensate

Gas hydrates (frozen methane)Non-commercial today

AT SUBSURFACE P/T CONDITIONSmonophasic

Bitumen Tar

Poor economy to non-commercial

Commercial Hydrocarbon Fluids

Liquids

Solids

transportable

Tanker

Pipeline transportable

Need nearbymarket

Gas difficult to store

Liquids easy to store

Hydrocarbons - a continuum of increasingly complex compounds of hydrogen and carbon, with many accessory components, including sulphides, CO2 and heavy metals.

Light Compounds Heavy compounds

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FLUIDSTypical Hydrocarbon P/T Phase Diagram

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FLUIDSTypical Fluid State Phase Diagrams - Oils

High energy system

Low energy system

Unsaturated Oil:

At the reservoir temperature the bubble pressure is less than the bottom hole pressure

Saturated Oil:

The bubble pressure is equal to the bottom hole pressure. The slightest fall in pressure results in two phase production

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FLUIDSTypical Fluid State Phase Diagrams - Gases

Condensate Gas:The bottom isotherm cuts the fluid dew point curve. Depletion results in deposition of condensate in the reservoir.

Wet Gas:The bottom isotherm is to the right of the cricondotherm and the surface conditions are in the two phase region. The gas gives rise to condensate on the surface under normal test conditions, but not in the reservoir.

Dry Gas:The bottom isotherm is to the right of the cricondotherm and the surface conditions are outside the two phase region. This fluid does not give rise to any surface condensate under normal test conditions, it is always possible to obtain liquid by processing this gas at low temperatures

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FluidsOil Density versus API Gravity

Oil Density vs API Gravity

05

101520253035404550556065

0.74

0.76

0.78

0.80

0.82

0.84

0.86

0.88

0.90

0.92

0.94

0.96

0.98

1.00

Density g/cc

Gra

vity

API

Very Heavy Oil

Heavy Oil

Normal Oil

Light Oil

Condensate

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FluidsFormation Pressure and Fluid Composition

PRESSURE vs GLR

250

300

350

400

450

500

10 100 1000 10000 100000GLR m3/m3

PRES

SUR

E ba

rs

No Complex Fluids at Lower Pressures

COMPLEX FLUIDOIL GAS

DIPHASIC

MONOPHASIC

NORMAL OIL LIGHT OIL CRITICAL FLUID CRITIQUE

GAS RICH IN CONDENSATE GAS CONDENSATEHEAVY OIL WET GAS

25API 43API 48API 57API APPROXIMATE API GRAVITY VALUES

52API39API

9

FLUIDS - Distribution The distribution of hydrocarbon fluid types is

controlled by the geological evolution of Pressure/Temperature conditions during maturation migration accumulation retention leakage - recharging..

It is a complex subject and it is difficult to accurately predict the fluid composition of a prospect prior to drilling.

However, the position of a play in a petroleum system is frequently used to estimate the probable producible fluid:

Hot and deep = gas prone Shallow and low temperature = heavy oil Between, anything is possible!

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FLUIDS Oil Shrinkage Factor The oil shrinkage factor

(Bo) is used to convert calculated subsurface volumes to surface volumes (stock tank barrels) at standard temperature and pressure.

The shrinkage is due to the exsolution of dissolved gas.

Low GOR oils have low Bo values close to unity.

High GOR oils have high Bo values ~ 0.5

+

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FLUIDS Gas Expansion Factor

The gas expansion factor (Bg) is used to convert reservoir volumes to surface volumes (m3) at standard temperature and pressure.

Gas increases in volume from reservoir to surface due to decreased temperature and pressure.

This increase in volume very significant, e.g. at 3000m the Bg factor usually ranges from 250 to 300.

12

FLUIDS Other Hydrocarbons

Other hydrocarbons that are generally uneconomic to exploit are:

Bitumen (Tar) e.g. Athabasca Tar sands, Canada. Gas hydrates Frozen Methane.

Neither resource can currently be extracted at commercially viable rates compared to conventional oil and gas.

Hence no further discussion here.

13

FLUIDS Recovery Factor The recovery factor is the fraction of in-place oil

or gas that is producible, expressed as %. A great deal depends on the reservoir drive

mechanism and secondary and tertiary methods used to produce the fluids.

Gas is extremely mobile and purely by depletion/gas expansion, the resultant recovery will be high.

Oil is less mobile and subject to poorer recovery rates.

Hence the inclusion of fluid type as a criterion in Play and Prospect evaluation.

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FLUIDS Recovery Factor

Typical ranges of primary plus secondary recovery values:

OilSandstones 21 - 37 52%Carbonates 27 - 42 52%

GasSandstones 50 - 65 80%Carbonates 65 - 80 95%

But the drive mechanism plays a major role

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Resources Categories

16

FLUIDS Primary Oil Recovery MechanismsSecondary and tertiary methods commonly used to improve recovery efficiencye.g. gas lift, water injection, miscible gas injection.

17

FLUIDS Primary Oil Recovery MechanismsNatural Depletion Drive:

Low recovery efficiency

Small traps, low GOR oil

Little to no aquifer support

Bulk of oil production early on

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FLUIDS Primary Oil Recovery Mechanisms

Solution Gas Drive: Isolated traps, moderate GOR oil

Low to moderate recovery efficiency

Little to no aquifer support

Bulk of oil production early on, then gas with slow decline.

19

FLUIDS Primary Oil Recovery Mechanisms

Gas Cap Drive: Saturated oil in a trap with a free gas cap

Moderate recovery efficiency

Little to no water drive

Bulk of oil production early on, then gas slowly building.

20

FLUIDS Primary Oil Recovery MechanismsNatural Water Drive:

Under-saturated oil in a trap with a regionally extensive reservoir

Good to excellent recovery efficiency

Large aquifer

Reservoir heterogeneity converts bottom to edge drive

Long oil production plateau period, gas production fairly constant, water rises severely towards end.

21

FLUIDS Primary Oil Recovery MechanismsCompaction Drive:

Under-saturated and heavy oil in an isolated trap at shallow burial depths

Poor to moderate recovery efficiency

Little to no aquifer

Reservoir unconsolidated

Very slow oil production decline.

22

FLUIDS Primary Oil Recovery MechanismsGravity Drive:

Under-saturated and heavy oil in high structural relief trap

Poor to moderate recovery efficiency

Little to no aquifer

Reservoir with great lateral continuity

Bulk of oil production early on, then gas building at end.

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FLUIDS Gas Recovery Mechanisms

24

FLUIDS Gas Recovery MechanismsNatural Depletion Drive:

Good to excellent recovery efficiency

Isolated traps, low GCR dry gas or wet gas

Little to no aquifer support

Gas production maintained at constant rate through export line (contract for sales)

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FLUIDS Gas Recovery MechanismsGas Recycling:

Good to excellent recovery efficiency

Isolated traps, high GCR wet gas with condensate

Little to no aquifer support

Inject dry gas to increase condensate recovery.

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FLUIDSA Simplified Classification

Franais CODE EnglishHUILE: normale, lourde. FO OIL: normal, heavy.GAZ: gaz sec, ,gaz humide, gaz condensat. FG GAS: dry gas, wet gas,gas-condensateFLUIDE COMPLEXE: gaz riche en condensat, fluide critique, huile lgre. FC

COMPLEX FLUID: gas rich in condensate, critical fluid, light oil.

BITUME FB BITUMEN: tarHYDRATE FH GAS HYDRATES

HYDROCARBON FLUIDS GOR/GLR RELATIONSHIPS

1

10

100

1000

10000

100000

1000000

10000000

1 10 100 1000 10000 100000 1000000

GLR m^3/m^3

GO

R s

cf/b

bl

Normal Oil

Dry Gas

Wet Gas

Gas - Condensate

Gas rich in Condensate

Critical Fluid

Light Oil

Heavy Oil

Dead Oil

COMPLEX FLUIDS

GAS

OIL

GA

Z

FLU

IDE

CO

MPL

EXE

HU

ILE

Gaz

sec

Gaz

c

onde

nsat

Gaz

hum

ide

Gaz

rich

e en

co

nden

sat

Flui

de C

ritiq

ue

Hui

le E

xtra

Lo

urde

Hui

le L

gr

e

Hui

le M

orte

Very Heavy Oil

Hui

le L

ourd

e

Hui

le N

orm

ale

39API

48API

25API

52API

57API

43API

10API

Valeurs de gravit approximatives

3 PRINCIPAL TYPES OF FLUID ( 2 SUPPLEMENTARY TYPES)

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FLUIDS CLASSIFICATIONHYDROCARBON FLUIDS GOR/GLR RELATIONSHIPS

1

10

100

1000

10000

100000

1000000

10000000

1 10 100 1000 10000 100000 1000000

GLR m^3/m^3

GO

R s

cf/b

bl

Normal Oil

Dry Gas

Wet Gas

Gas - Condensate

Gas rich in Condensate

Critical Fluid

Light Oil

Heavy Oil

Dead Oil

COMPLEX

FLUIDS

GAS

OIL

GA

Z

FLU

IDE

CO

MPL

EXE

HU

ILE

Gaz

sec

Gaz

c

onde

nsat

Gaz

hum

ide

Gaz

rich

e en

cond

ensa

t

Flui

de C

ritiq

ue

Hui

le E

xtra

Lour

de

Hui

le L

gr

e

Hui

le M

orte

Very Heavy Oil

Hui

le L

ourd

e

Hui

le N

orm

ale

39API

48API

25API

52API

57API

43API

10API

Valeurs de gravit

approximatives

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FLUIDS

FLUIDSFLUIDSFLUIDSFLUIDSFLUIDSFLUIDSFluidsFluidsFLUIDS - DistributionFLUIDS Oil Shrinkage FactorFLUIDS Gas Expansion FactorFLUIDS Other HydrocarbonsFLUIDS Recovery FactorFLUIDS Recovery FactorResources CategoriesFLUIDS Primary Oil Recovery MechanismsFLUIDS Primary Oil Recovery MechanismsFLUIDS Primary Oil Recovery MechanismsFLUIDS Primary Oil Recovery MechanismsFLUIDS Primary Oil Recovery MechanismsFLUIDS Primary Oil Recovery MechanismsFLUIDS Primary Oil Recovery MechanismsFLUIDS Gas Recovery MechanismsFLUIDS Gas Recovery MechanismsFLUIDS Gas Recovery MechanismsFLUIDSFLUIDS CLASSIFICATIONFLUIDS