Wiekert Visser

Oil & Gas typing

Introduction & bulk properties

Petroleum systems mapping work flow

Oil Oil correlation

Oil Gas correlation

Gas Gas correlationOil/gas family map

Oil Source rock correlation

Gas Source rock correlationDefine Petroleum Systems

Rock Eval analyses (wells)

Seismic isopachs mapSource rock quality maps

Maturity data (wells) Source rock kitchen maps

(Once) Active Petroleum Systems maps

Note: modern 3D modeling tools need much more data & deliver superior results

Objectives of oil and gas typing in Exploration

Typing of oil, gas, and source rock extracts is a key

element of Petroleum Systems Analysis. This work

aims at:

Assessment of the source of the hydrocarbons (type and age)

Assessment of the maturity of the source at the time of expulsion

Estabishing the petroleum system (i.e. The link betweensource rock and trapped hydrocarbons)

Oil family mapping: is there more than 1 petroleum system in the basin?

Reduction of exploration risk by the above activities.

Example exploration question

AB C

Source rock A (KK)

Oil field1

2

3

4

0

Top oil window (VR=0.6)

? Source rock B (JJ) ?

Depth

(km

)

Question: Is the oil derived from the Cretaceous or the

Jurassic source rock?

Mature

Immature

D

Fundamentals of oil & gas chemistry

Crude oil is a mixture of thousands of organic

components. Chemical analysis of these complex

mixtures gives information about:

Economic value of the oil/gas

The source & charge history

Post-trapping alterations

A condensate is operationally defined as any fluid which is a gas in the

subsurface but a liquid at the surface. This depends on the PVT

conditions. For geochemical purposes, a condensate is a fluid with most

of its mass below C15.

Gas Condensate Oil

API gravity n.a. >45 20 %

Methane content > 95 % 60-85 % < 20 %

GOR (scf/bbl) > 100.000 3000 100.000 < 3000

Bulk Characteristics of Petroleum Fluids

Oil and Gas compounds, fundamentals

n-Alkanes: CnH2n+2

Cyclo-pentane

H2 H2

H2 H2

H2H2

Cyclo-hexane

C6H12

Benzene

C6H6

H

|

H C H

|

H

H H H H H

| | | | |

H C C C C C H

| | | | |

H H H H H

Methane Pentane

C5H12C1 C5 Iso-C6

Pentane

Paraffins/Alkanes

Cyclo-alkanes

(Naphtenes)

n-alkanes

iso-alkanes

Aromatics

Non-saturates

Saturates: alkanes

Saturates: naphtenes

Naphtalene

Composition of a 35 API & a 16 API crude

16 API

0

Main boiling fractions of oilDown-stream purposes

Normal black oil

Bulk properties of oils for E&P

API gravity (density)

weight-loss on topping

% Sulfur

Heavy metals

Carbon Isotopes

Gross Composition:

% Saturates,

% Aromatics

% Hetero compounds

Total Acid Number (TAN)

Viscosity

Pour point

Cloud point

Wax content

Asphaltene content

Geological Applications (Reservoir) Engineering

i

i

i

F

API gravity - density relationship

Specific gravity

Condensate

Oil

API gravity

Tar

Degrees API= -131,5141,5 specific gravity

R

Tambaredjo Oil

API Gravity versus %S

Global data set trend

Amongst heavy oils

the Tambaredjo crude

is of high quality, and very

exceptional in composition

Sulphur in Shaly Marine Oils

The percentage of Sulphur is

important for crude market price,

and for corrosive effects.

Masila: 30.5 / 0.67%

Marib Light: 48 / 0.08%

Hemiar: 22.2 / 1.23%

The variation in the percentage of

Sulphur in the Yemeni crudes is

related to biodegradation.

These data are from the Jurassic Madbi marly shales in Yemen

Interpreting Sulfur

Sweet low sulfur crudes indicate the source is:

High API gravity shaly marine

Lacustrine (in case of elevated wax content)

Landplant (in case of high wax content)

Souer high sulfur crudes indicate that:

Source is a limestone (with very low shale content)

Crude has been biodegraded (in case of low API)

Crude is a low maturity early expulsion product (in case of

low API)

R

C = -1 *100013 C / C (sample)

13 12

C / C (standard)13 12

[ ]

The standard is the belemnite from the PeeDee Formation in South Carolina

PDB C = 013

Carbon isotopes

The atom Carbon has three different isotopes 12C, 13C, 14C, with atomic

weight of 12, 13, and 14 gram/mol respectively.

12C is most abundant, and living organisms prefer 12C over 13C

14C is least abundant and is radio-active. It can be used as dating tool.

Carbon Isotopes in Nature

-100 -80 -60 -40 -20 0 20

-100 -80 -60 -40 -20 0 20

13 CPDB ()

Diamond

Animal Bone

Thermal Gas

Bacterial Gas

Wood

Peat

Non-marine Carbonate Minerals

Groundwater HCO3

Plankton

Land Plants (C4)

Land Plants (C3)

Marine HCO3

Marine Plants

Marine Carbonate Minerals

Atmospheric CO2

Coal

Bakken Shale

West Africa

North Sea

Cretaceous

Kimmeridge

WyomingPhosphoria

Williston Basin

Ordovician Texas

-20-25-30-35

Monterey

Oils / Source Rocks

Oils/SR

Carbon isotopes are

very useful for Oil Oil

and Oil Source rock

correlations

R

Isomers of alkanes

C2 C5C4 C9C8C7C6 C11 C13

1 92 3 5 18 35 159 802

1 42 2 3 5 6 7 8

Carbon atoms in molecule

Isomers

Possible

Significant in

crude oils

The number of isomers in crude oils explodes with increasing carbon number.

Analysing all these compounds required excellent separation techniques, such as

liquid and/or gas chromatography, and mass spectrometry

C-C-C-C-C-C-C

n-C7Branched alkanes C7 ring compounds

Example of branched alkanes: C7 isomers

1* Tri-branched

3* Mono-branched

4* Di-branched

Long chain iso-alkanes: Pristane and Phytane

CH3

CH3 CH3 CH3

CH3

CH3

CH3

CH3 CH3 CH3

CH3

CH3

Phytane

Pristane

Pristane and Phytane occur in all crude oils

Both compounds are fragments of Chlorophyll,

which occurs in many living organisms

C20

C19

Pristane and Phytane are simple indicators for environment of

deposition and a basic tool for correlation. They are maturity

dependent, but reasonably resistant to biodegradation.

Biomarkers in oil and in living organisms

CH3

CH3

CH3

CH3

CH3

CH3

CH3

CH3

CH3

CH3

HO

CholesterolPresent in living organisms

CholestanePresent in crude oil

This biomarker occur in virtually all crude oils

Many biomarkers are detailed indicators for environment of

deposition and age of the source rock and are the most

important tool for correlation. They are slightly maturity

dependent, but resistant to biodegradation. Biomarkers are

the work-horse for exploration geochemists.

Conclusions

Analyses of oil and gas are essential input for the

assessment of Petroleum Systems

Fluid properties contain geological information that

can be used for inpout as well as for calibration of

petroleum systems models.