Lesson-7: Oil-Oil

and Oil-Source Rock

Correlation (a)

Introduction to Petroleum Geochemistry

Further Readings

Bissada, K.K. et al, 1992, “Geochemical Inversion –

A Modern Approach to Inferring Source Rock Identity

from Characteristics of Accumulated Oil and Gas”,

Proc IPA Convention

Curiale, J.A., 1994, “Correlation of Oils and Source

Rocks – A Conceptual and Historical Perspective”,

AAPG Memoir 60, Chapter-15

Waples, D.W. and J.A. Curiale, 1999, ”Oil-Oil and

Oil-Source Rock Correlations”, AAPG Treatise

Handbook Vol 3, Chapter-8

Petroleum System:

Source Rock – Migration – Traps – Preservation

Processes:

Generation

Migration

Accumulation

Preservation

Elements:

Source Rock

Migration Route

Reservoir Rock

Seal Rock Trap

Petroleum System Definition

The essential ELEMENTS and PROCESSES and all genetically-related hydrocarbons that occur in petroleum shows and accumulations whose provenance is a single pod of active source rock

ELEMENTS

Source Rock

Migration Route

Reservoir Rock

Seal Rock

PROCESSES

Generation

Migration

Accumulation

Preservation Trap

AAPG

Oil and Gas Fields Distribution

Oil and Gas Fields Distribution

Why some fields contain gas?

Others only gas?

Which fields sourced from Talang Akar?

Any other source rocks?

Further exploration potential?

Genetic Relationship of Trapped Oil and Sources

Objectives

Genetic relationship of oil – source rock(s)

Group oils into genetic families and postulate potential mixing

Determine how many effective source rocks exist

Envisage migration pathways – thus opens up potential extension of current plays

Given in 3 lectures

Basic Concepts

Oil inherits certain properties of the source

rock thus oil can be genetically correlated to

its source rock

Two or more oil pools generated from same

source rock can genetically be correlated

A model may then be developed to infer

migration and trapping to allow searching for

additional pools to be found

Genetic Correlation

Oils can be correlated to source rock by comparing

parameters to the extractable organic matter

(bitumen) parameters that may lead to identification

of:

Organic Matter type of the source rock

Depositional Environment of the source rock

Maturity level of the source rock

Basic Concepts-1

Crude oil correlated with

other crude oils from

different fields and with

Rock Extracts (bitumen)

by comparing parameter

similarities

High similarities –

positive correlation

Low similarities –

negative correlation

Basic Concepts-2

When source rock

candidate NOT

AVAILABLE:

Crude oil correlated with

Other crude oils from

other fields by comparing

parameter similarities

Source rock facies and

maturity may be inferred

from biomarkers and

other properties

Correlation Techniques

Bulk Parameters

API Gravity

Sulfur Content

C15+ Compounds (Saturates, Aromatics, Resin/Asphaltenes)

Gas Chromatography:

Whole Oil

Saturates

Isotopes:

Carbon: 13C (mostly)

Hydrogen: D/H (Deuterium / Hydrogen) ratio

Sulfur: 34S/32S

Biomarkers (Molecular Fingerprinting)

API Gravity vs Sulfur Content

Both API and Sulfur content affected by maturity level

Presence of sulfur (>0.5 %wt) suggests marine environment

Low sulfur (< 0.5 %wt) – terrestrial sourced

High sulfur (>2 %wt) - carbonate sourced

Be careful with secondary sulfur

Australian Oil Samples

Cross plot of onshore and offshore oils from

the East Java Basin based on physical bulk

properties and pristane/phytane

Ternary Plot of Paraffins – Naphthenes – Aromatics

Ternary Diagram of Paraffins – Naphthenes and Aromatics+NSO

Possible Mixing of Source Rocks

Gas Chromatography

May be performed on:

Whole oil

Saturated Fractions

Light ends

Heavy ends

Petroleum and Petroleum Products

Schematic Diagram of

Gas Chromatography

• Saturates Fraction GC

• Whole oil GC

Gas Chromatogram of a high-wax oil of terrestrial origin with an odd carbon

preference (CPI) in the wax region and a high pristane–phytane ratio typical of

coaly or certain nearshore aquatic environments

Significant input of terrigenous organic matter is indicated by a bimodal n-alkane

distribution (a second mode in the wax region, from n-C23 to n-C31), a pristane–

phytane ratio greater than 2.0, and a strong odd-carbon n-alkane dominance from

n-C25 to n-C31

These features are characteristic of deltaic or lacustrine sourced oils (in this case

from Indonesia)

GC Analysis and Crude Alteration

Schematic of Oil & Gas Formation/Destruction

Organic Matter

(Kerogen) Bitumen

CO2

Oil/Gas Primary

Cracking

Wet

Gas

Dry

Gas

Pyrobitumen

Biodegradation

Secondary

Cracking

Secondary Cracking /

Thermal Cracking due to

deeper burial of the

accumulated oil

160 oC (320 oF)

Ro ~ 1.1%

200 oC (390 oF)

Ro ~ 1.5%

Gas Chromatograms of two oils from Wyoming. Both were sourced from the Permian Phosphoria Formation, but are reservoired in different fields

The bimodal distribution of n-alkanes in the top oil is consistent with a lower level of maturity than that of the unimodal oil at the bottom

Comparison of these oils using gas chromatography for the purpose of oil–oil correlation must be done with caution because of the maturity differences

Gas Chromatograms of saturated hydrocarbons from an immature extract of coaly organic matter (top) and an oil with a fairly high wax content believed to have been sourced from a similar facies (bottom)

Both show many of the same characteristics — high wax content, odd-carbon preference in the wax range, high pristane–phytane ratio—but maturity effects have changed many of the details

Immature Coaly Rock Extract

Oil

Mature vs Immature Oil GC

Thank you

for your attention