1. Basin Analysis & Petroleum System QAB3033
Assoc. Prof. Dr. Swapan Kumar Bhattacharya
Geoscience & Petroleum Engineering Department
PAB 1023 Petroleum Geoscience

2. Fundamentals of Petroleum Geology Prospect & Play Analysis
Petroleum System
This Week
Fundamentals of Petroleum Geology
Source Rock Generation
Elements Reservoir Rock Processes Migration
Seal Rock Accumulation
Overburden Rock
Prospect & Play Analysis

3. Prospect & Play
Prospect - a lead which has been fully evaluated and is ready to drill.
Play - A particular combination of reservoir, seal, source and trap associated with proven hydrocarbon accumulations.

4. Source Rock Source Rock is defined as the rock having efficient
hydrocarbon generation and expulsion capacities.
Characteristically, these are fine grained sedimentary
rocks with high total organic carbon (TOC), high molar
H/C ratio.
Their thermal maturity (Vro) need to be sufficient so
that at least they cross oil or gas Window for
specific oil or gas generation.

5. Reservoir Rock
Reservoir Rock is defined as the rock having appreciable porosity to trap the hydrocarbons and sufficient permeability for the oil to flow during migration and production.
Characteristically, these are coarse grained clastic sedimentary rocks or porous limestones or fractured igneous or metamorphic rocks.

6. Hydrocarbon Traps Hydrocarbon Traps are:
Structural: If trapping is exclusively due to structural style, or
Stratigraphic: If trapping is exclusively due to stratigraphic disposition, or
Combination: If trapping is due to both structure & stratigraphic disposition.
Structural Traps: Folds, Faults
Stratigraphic Traps: Lenticular Sands, Channel fills
Combination Traps: Up-dip pinchouts

7. PAB 1023 Petroleum Geoscience
Structural Traps
Structural traps are those where entrapment of hydrocarbon takes place due to structural configuration only. Structural traps form usually by tectonic forces.
An anticline is where rocks are folded or bent upwards. Hydrocarbons migrate up the flanks of the anticline and are trapped in the crest.
Faults occur where there is movement along a joint or fracture. Offset of the beds could result in an impermeable layer being on top of a permeable layer.
PAB 1023 Petroleum Geoscience

8. PAB 1023 Petroleum Geoscience
Structural Traps :
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9. Structural Traps Terminology
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10. PAB 1023 Petroleum Geoscience
Six trapping and two non-trapping configurations against a fault, depending on whether the fault is normal or reverse, on the direction of dip of the beds relative to the fault plane, and on the amount of displacement of the reservoir.
PAB 1023 Petroleum Geoscience

11. PAB 1023 Petroleum Geoscience
Sealing Faults
An investigation into the sealing qualities of faults affecting roll-over anticlines in the Niger Delta, where the reservoirs overlie overpressured shales (bulging).
Where a reservoir is full to spill-point against a fault, and where an oil-water contact is continuous across a fault, it is presumed that the fault is non-sealing; elsewhere it appears to form a trap. The difference is believed to be due to clay being smeared into the fault plane, where there is enough of it in the section, as the fault moved
PAB 1023 Petroleum Geoscience

12. PAB 1023 Petroleum Geoscience
Sealing Faults
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13. PAB 1023 Petroleum Geoscience
Stratigraphic Traps
Stratigraphic traps are those where entrapment of hydrocarbon takes place due to stratigraphic disposition only.
Rock layers changing from a good reservoir to non-reservoir due to change in rock type (pinch-out), reservoir quality (diagenesis), or removal (erosional unconformity)
PAB 1023 Petroleum Geoscience

14. PAB 1023 Petroleum Geoscience
Pinch Out
Sometimes due to a lateral change in the environment of deposition a lens of permeable sand is surrounded by less permeable siltstones and shales, forming a pinch out trap.
This commonly happens in stream environments where sand is deposited along the stream channel which is surrounded by a flood plain characterized by finer grained sediments.
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15. PAB 1023 Petroleum Geoscience
Channel Trap
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16. PAB 1023 Petroleum Geoscience
Unconformity
Unconformities are another type of stratigraphic trap.
They represent a gap in the geologic record, in other words a period of erosion and/or nondeposition.
They can result in a permeable reservoir rock being truncated and overlain by an impermeable unit.
PAB 1023 Petroleum Geoscience

17. PAB 1023 Petroleum Geoscience
Hydrodynamic trap
Oil, attempting to escape to surface up a reservoir, is held against an unevenness of its upper surface by water flowing in the opposite direction. There is no structural or stratigraphic closure.
Note that the oil-water contact is tilted down in the direction of water flow.
PAB 1023 Petroleum Geoscience

18. PAB 1023 Petroleum Geoscience
Diapiric Traps
Caused by upward movement of sediments that are less dense than those overlying them
Salt
Clay
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19. Salt Dome Associated Traps
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20. PAB 1023 Petroleum Geoscience
Seal
A seal is a fine-grained rock that prevents the oil migrating to the vertical migration (which happens in many parts of the world - leading to natural oil seeps).
The seal is an important component in a prospect.
PAB 1023 Petroleum Geoscience

21. PAB 1023 Petroleum Geoscience
SEAL
Common seals include
salt evaporites, chalks provides an effective seal, but
clay-rich mudrock, shale represent most seals.
Siltstones (very fine-grained)
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22. PAB 1023 Petroleum Geoscience
HOW WE QUANTIFY SEAL?
Analysis of seals involves assessment of their thickness and extent, such that their effectiveness can be quantified.
Knowledge of sequence stratigraphy is crucial for better understanding of seal.
PAB 1023 Petroleum Geoscience

23. Petroleum System A petroleum system includes all those geological
elements & processes that are essential for an oil
deposit to exist in nature. (Magoon, 1988)
These basic elements are:
Petroleum Source rocks
Reservoir Rocks
Seals
Migration Paths
Traps
And the geological processes
that created each of them
Source Rock
Migration Route
Reservoir Rock
Seal Rock
Trap
Generation
Migration
Accumulation
Preservation

24. Petroleum System Processes
Accumulation
Source Rock

25. e.g La Luna – Misoa (!) Marcaibo Basin, Venezuela.
Petroleum System
The term petroleum includes high concentrations
of either thermal or biogenic gas, condensates,
crude oils, natural waxes, or asphalts found in both
conventional & in tight reservoirs, fractured shales,
gas hydrates, coal beds and bituminous sandstones.
The name of a petroleum system is a combination
of the source & reservoir rock names followed by
a symbol indicating the level of certainty of the
source – reservoir association. The symbols are:
Known (!)
Hypothetical (.)
Speculative (?)
e.g La Luna – Misoa (!) Marcaibo Basin, Venezuela.

26. Petroleum System Petroleum system is best described by:
Table listing all the field names, year of
discovery, name of producing unit, depth,
reservoir seal lithology, trap type, cumulative
production & reserves.
A map showing the geographic extent of
the system, matured source pod , location
of fields & key wells etc.
A burial history chart at one or more locations.
A geologic cross-section drawn at the critical
moment illustrating the spatial relationship of
the essential elements.
An event chart indicating the time intervals of
the essential elements & processes including
preservation time & critical moment.

27. Petroleum System

28. GEOGRAPHIC EXTENT OF PETROLEUM SYSTEM
Present-Day Petroleum System
GEOGRAPHIC EXTENT OF PETROLEUM SYSTEM
Present-Day A
Trap A’
STRATIGRAPHIC
EXTENT OF
PETROLEUM SYSTEM
Basement
Overburden
Seal
Petroleum accumulation
Reservoir
Top of oil window
Source
Bottom of oil window
Underburden
Magoon and Dow, 1994

29. Petroleum System

30. Petroleum System

31. Petroleum System

32. Petroleum System Formulae to calculate hydrocarbon generation
M (g.TOC) = V (cm3) x p (g/cm3) x [TOC(wt%) /100]
R (mg HC/g TOC) = HI0(mg HC/g TOC) – HIp (mg HC/g TOC)
HCG (kg HC) = R xM x 10-6
Oil (bbl) = HCG / (kg/bbl of 400 API oil)

33. Total Petroleum System
Reasons for carrying out oil and gas related investigations
in a geologic province are :
To decide where to explore and / or
To assess undiscovered commercial quantities of petroleum
Both can be assessed by ‘Petroleum System’
In USGS World Petroleum Assessment, 2000 the term
‘Total Petroleum System’ was introduced to evaluate undiscovered oil and
Gas resources that have the potential to be added within the next 30 years
To reserves in the world.

34. Total Petroleum System
The ‘Total Petroleum System is evaluated by dividing the world into eight (8)
regions and 937 geological provinces. Maps were prepared for each region
using GIS and each region and province is named and numbered. Each
province is characteristically hundred or even thousand square kilometers
encompassing a natural geological entity – a basin, a thrust belt, a delta or
some combination of geological entity. These provinces are then ranked by
known volume of petroleum in barrels.

35. Total Petroleum System
The goal of ‘TPS’ investigation is to understand the geographic,
stratigraphic and temporal evolution of the system so that the resource
assessment can be based on sound geologic and geochemical concepts.
‘TPS’ ideally includes :
Genetically related known oil and gas accumulations, shows and seeps
The pod or pods of active source rocks
Minimum geographic extent
Maximum geographic extent.
The location of the TPS cross-section and
The location of the locality depicted in the burial history chart.

36. Total Petroleum System
1. Discovered accumulations, shows and seeps:
Within a given TPS, the genetically related discovered oil and gas
fields or petroleum accumulations originated from same pod of active
source rock. The investigator starts with a map that shows the discovered
oil and gas fields. The investigator then groups the oil and gas fields into
one or more possible TPS based on their geographic and stratigraphic
locations and the bulk and geochemical properties of the fluids in each
accumulation.
2. Pod of active source rock:
The pod of active source rock is a contiguous volume of source
rock that generated and expelled petroleum at the critical moment and is the
provenance for a group of genetically petroleum shows, seeps and
accumulations in a TPS. A pod of active source rock may be active, inactive
or spent.

37. Total Petroleum System
3. Minimum geographic extent:
The minimum geographic extent of the TPS is a line that
circumscribes the pod of active source rock and includes all the discovered
Petroleum shows, seeps and accumulations that generated from this pod.
This is the same line of the geographic extent of the petroleum system.
4. Maximum geographic extent:
The maximum geographic extent of the TPS is line that lies beyond
or coincides with minimum geographic extent. The maximum geographic
extent is mapped using geological evidence, such as the geographic extent
of the reservoir rock, the indicates the possibility that oil and gas migrated
beyond the minimum geographic extent but no seeps, shows or accumulations
are known.

38. Total Petroleum System

39. Total Petroleum System

40. Source Material Non-Biogenic Origins Biogenic (Kerogen Types)
Type I – Algal (oil prone) sapropelic
Type II – Mixed
Type III – Woody (gas prone) humic
Host rock (Shales and Coals)

41. 1 2 15 10 8 9 2 7 11 12 6 3 13 4 14 5

42. TOC
Vro
Well
Thickness
These data are available
with data package. Other
data you have to purchase
@ USD1000
You are asked to evaluate
and bid for the exploration.

43. Kerogen Types
Type 1
Type 2
Type 3