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Introduction to Petroleum Systems Analysis

Event chart

Charge Modelling

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Elements of a Petroleum System

Source rock Reservoir rock

Seal rock

Traps

Overburden rock Timing

Petroleum System Processes

Trap formation

Generationmigrationaccumulation of hydrocarbons

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Steps Required to Identify a Petroleum system

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Naming a Petroleum system

The name of A Petroleum System contains of 3

parts:

The name of active source rock

The name of the reservoir rock that contains the

largest volume of in-place petroleum

The Symbol expressing the level of certainty

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Level of certainty Criteria Symbol

Known A positive oil-source rock or gas-

source rock correlation

(!)

Hypothetical In the absence of a positive

petroleum-source rock correlation,

geochemical evidence

(.)

Speculative Geological or geophysical evidence (?)

Naming a Petroleum system (contd)

A petroleum system can be identified at 3 levels of certainty:

Known, Hypo thetica l And Speculative

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Petroleum System Event Chart

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Basin modelling in combination with geochemistry

provides the answers to the following questions:

Are there potential source rocks in a basin?

Can they produce oil and gas?

Have they produced oil and gas?

How much oil and gas have they produced?

When did they produce oil? When did they produce gas?

Where in the basin have they produced the oil and gas?

Where have the produced oil and gas migrated?

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1-D Charge Modelling

Simulation of key wells

Advantages:

Gives a quick basin appraisal.

Provides general trends of subsidence, thermal maturation and hydrocarbon

generation.

Disadvantages:

The well may not be representative of the whole basin.

Computed results may have large error limits.

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3-D Charge Modelling

Basin Simulation with the correct geometry

Advantages:

Combines all geophysical, geological, geothermal, geochemical and

pressure data in an integral manner

Give a full range of information for exploration representing present

level of know how

Disadvantages:

Time consuming and expensive

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Charge Modelling Input Parameters

Stratigraphic Thermal Calibration

Layer Subdivision

Depth

Age Erosion

Water Depth

Present day heat flow

Palaeoheat flow

Surface Temperature

Vitrinite Reflectance

Bottom Hole

Temperature

Biomarkers

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Methodology for modelling using TerraMod

Start

Input Data: Porosity

Lithology

Age

Heat Flow

Layer

Event type

Water depth

Surface temp.

Simulate

Is calculated

thickness VS

measured

thickness >

10%

Check lithology and or

porosityYES

NO

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Input Source rock

& Calibrated data

Calibration of model

(sensitivity & tuning)

Does

Calibrated &

modelled VR

data match?

Output model

result

End

Check heat flow and or

unconformity thickness

Methodology (Contd)

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Model input data on TerraMod

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Palaeoheat Flow Optimisation

Calibrated Modelled VR vs. Measured VR data

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1. Heat flow is adjusted over

last 5 Ma until calibration is

achieved between real and

predicted BHT data.

2. Curve should sit to the right

of the control points because

the real BHT always under

estimates the geothermal

gradient

Present Day Heat Flow Optimisation

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Geohistory Plot

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Sensitivity Analysis of Charge Model

Test the Significance of Input data on charge modelling results

- Procedure

Vary values within predefined realistic values

- Outcomes

Tests overall sensitivity of the model