08 chapter 08 habitat of HC in sedimentary basins new

Introduction 8.1-The Sedimentary Basin Concept 8.2-Sedimentary Basin Classification 8.3-Distribution of petroleum – rich basins... • Petroleum enrichment, the incidence of giant fields,

THE HABITAT OF HYDROCARBONS IN SEDIMENTARY BASINS

HCMUT-2014

Chapter 08:

Introduction

8.1-The Sedimentary Basin Concept

8.2-Sedimentary Basin Classification

8.3-Distribution of petroleum – rich

basins.

There are approximately 600 sedimentary rock basins in the world

A quarter of them are producing petroleum

Before exploitating in a new area , attemting to

locate drillabe prospects , it is necessery to

establish the type of basin , what productive horizons it may contain and where they may

be broadly located

• Even though petroleum reserves can be

found in rocks of all ages, most giant fields

and most of the world's reserves occur in

sequences, of Late Mesozoic and Cenozoic age ( Figure 01) Paleozoic rocks probably had potential to generate hydrocarbons

equal to that of these younger rocks, but

there has been more time in which to

destroy all or part of the petroleum through uplift and erosion (Halbouty et al, 1970)

Fig: 01

• Worldwide reserves can be related to their location

within a petroleum basin, regardless of its basin type

(Figure: 02)

Fig: 02

8.1-The Sedimentary Basin Concept

• A general term for any large area of tectonic

origin with a thick accumulation of sedimentary rocks

• A basin is a geological structure with a unique

sequence of rocks that are dissimilar to those outside the basin

• A low area with no exterior drainage

• Include both depression itself and the

thicker-than-everage sediments that fill it

Fig: 03

Geometry of Sedimentary Basins

It is tempting to believe that a sedimentary

basin was deepest where its sediments

are thickest, but this is not necessarily true

Non-coincidence of depocenters, topographic low and point of maximum basement subsidence in a land-derived, prograding clastic wedge

Fig: 05

Sediment Fill

Basins can be characterized by the sediments

that fill them

They can be dominated by continental, shallow

marine, or deep marine sediments, depending

on their elevation and the interplay between the rate of subsidence and the rate of

sedimentation

Basin-Forming Mechanisms

• Basins form as a result of large-scale vertical

upper layers (fig 06-1) , which can be

explained through the widely accepted theory

of plate tectonics

• The earth's outermost shell is a rigid layer

called the lithosphere, which consists of

lows form on the earth's surface where the crust is thin, and composed of dense

basaltic rocks

The earth's outermost layers

Fig: 06-2

Initiation of rifting and ocean floor spreading over

continental crus

Fig: 08 Pre-rift domal bulge Fig: 09 Initial radial rift

21 Fig: 10 Early separation stage Fig: 11

MODEL OF A DIVERGING PLATE BOUNDARY

The separated continents are now far apart, and basins develop along their

Fig: 12

MODEL OF SUBDUCTING PLATE MARGIN

At a subduction zone, the leading edge of one plate overrides another, and the

overridden plate is dragged down into the mantle and consumed

Fig: 12

MODEL OF A COLLISIONAL PLATE MARGIN, COLLISION BETWEEN

OCEAN PLATE AND A CONTINENTAL MARGIN

Fig: 13

MODEL OF A COLLISIONAL PLATE MARGIN,

CONTINENT – CONTINENT COLLISION

Fig: 14

Transcurrent faulting along the conver plate margin in California

Fig: 15

8.2-Sedimentary Basin

Classification

• Many different basin classification

schemes have been proposed, as

geological thought has evolved from the

geosyncline concept to plate tectonics

• Petroleum enrichment, the incidence of

giant fields, and the habitat of petroleum

within sedimentary basins can be related to structural, sedimentological, and

geothermal settings, which can be used to describe a number of petroleum basin

types

• There are several general ways in which

sedimentary basins can be grouped

They can be divided on the basis of their underlying

material or crust:

•continental crust, which is relatively light, granitic and

underlies most continental areas; or,

•intermediate crust, compositionally between granite and

basalt and occurring along continent-ocean margins.

They may also be grouped according to the stability

and movement of this underlying crust, as either;

•cratonic basins, developed on the stable parts of continents away from continental margins;

•divergent-margin basins, formed along continental margins where the sea floor is spreading and rift-drift (extensional) movements occur; or,

•convergent-margin basins, formed along continental

margins where continents and/or oceans are in collision and some ocean crust may be consumed.

For the purpose of petroleum exploration,

however, we need a finer-tuned classification

scheme such as the ten-part basin classification scheme based on the work of Huff (1980) and

Klemme (1980), which is summarized in Figure

16.

In the petroleum industry, a classification is

needed that emphasizes the role of the

sedimentary basin as a container for oil and

gas.

34

There are a total of ten basin types:

• two that are related to stable continental

plates;

• two that develop through plate divergence;

• four that relate to plate convergence

• two other types, basins that downwarp (Open

& closed) into small oceans, form a separate class because of their unique petroleum

features

Basin classification

Fig: 16

Basin types and details

Stable continental plates:

38

Idealized pattern of an Interior basin

Fig: 17

Generalized cross-section through the Williston basin of the USA and Canada

Fig: 18

Major interior basins of the world

Fig: 20

Table 10.1 Interior Basin (Intracratonic, sag)

• Distinguishing features simple, single cycle; no uplands; in continental interiors.

• Depositional History mature, shallow water to non-marine sediments (clastic or carbonate prone); non-depositional or non-marine late stage.

• Reservoir equally sandstone or carbonate.

• Source shale.

• Cap shale, less commonly evaporite.

• Trap basement uplift arches and anticlines; combination and stratigraphic.

• Geothermal Gradient low to normal.

• Hydrocarbons low S, high gravity crude low natural gas

• Risks adequate traps; presence of shale for source and cap.

• Typical Reserves <0.5- 3 billion bbl hydrocarbon/basin

Foreland basin:

• Stable continental plates:

Idealized pattern of a foreland basin

Fig: 21

A typical foreland basin: The Permian basin of west Texas

Fig: 22

Fig: 24

Table 10 2 Foreland Basin (craton margin, composite)

• Distinguishing features multicycle basin on craton edge with adjacent uplift.

• Depositional History 1st cycle mature platform sediments; unconformity; 2nd cycle orogenic clastics.

• Reservoir mostly sandstone, lesser carbonate; in both cycles.

• Source overlying or interfingering shale; locally coal.

• Cap shale or evaporite.

• Trap mostly anticlines; some stratigraphic and combination

• Geothermal Gradient low to above average.

• Hydrocarbons mixed crude, similar to interior basins in 1t

cycle; above average deep thermal gas

• Risks trap efficiency; reservoir, source and seal development.

• Typical Reserves <0.5- 5 billion bbl hydrocarbon/basin

Rift Basin;

Pull-Apart Basin (passive

margin, divergent margin);

• Plate divergence:

Fig: 26

Fig: 28

The Suez basin of Egypt contained mostly thin Paleozoic and Cretaceous non-marine sands until it began to rift in the

Fig: 29

56 The CuuLong basin of Vietnam

The CuuLong basin of Vietnam

• Table 10.3 Rift Basin

• Distinguishing features downdropped graben over

continental crust; dormant divergence.

• Depositional History pre-rift rocks sedimentary, metamorphic

or granitic; post-rift fill is restricted facies, initially non-marine

that may become marine (either clastic or carbonate-prone).

• Reservoir equally sandstone or carbonate; of pre- and post-rift cycles.

• Source overlying or lateral facies shale.

• Cap basinwide evaporites or thick shale.

• Trap horst block anticlines; combination traps related high

blocks; tilted fault blocks.

• Geothermal Gradient normal to high.

• Hydrocarbons highly facies-dependent(paraffinic with

sandstone's; aromatic with carbonates); low to average gas.

• Risks small trap size; too high gradient; source shale

development.

• Typical Reserves <0.5- 30 billion bbl hydrocarbon/basin

Rift Basin;

Pull-Apart Basin (passive

margin, divergent margin);

• Plate divergence:

Idealized pattern of a pull-apart basin

Fig: 30

Fig: 32

The Gabon basin off the west coast of Africa Fig: 33

Table 10.4 Pull-Apart Basin (passive margin, divergent margin)

• Distinguishing features coastal half-grabens down-faulted

seaward; intermediate crust; result of ocean-floor spreading.

• Depositional History non-marine rift stage sediments;

restricted facies (carbonates, evaporites, black shale) in early separation; prograding clastic wedge in late separation stage.

• Reservoir sandstone in all three stages, some limestone in

early separation stage.

• Source overlying and interfingering shale.

• Cap shale or evaporite.

• Trap horst block, salt flow, roll-over and drape anticlines;

stratigraphic and combination

• Geothermal Gradient below average in marine stages.

• Hydrocarbons rift stage has paraffinic, intermediate gravity

crude; more aromatic, light gravity in separation stage; gas prone

• Risks kerogen maturation; biodegradation; pre-separation

source shales; post-separation reservoirs

• There are two types of basins that are found near subduction zones that have developed island-arcs

• Back-arc basins form between an island-arc and

continent (Figure 34 Idealized pattern of a back-arc

basin) They receive mostly shallow water

sediments Heat flow measured from back-arc

basins is high to very high, because of the melting and igneous activity of the island-arc

• Fore-arc basins lie between the island-arc and the ocean trench Their sediment facies are quite

variable and can range from fluvial to deep-sea fan

In contrast to back-arc basins, fore-arc basins have abnormally low heat flow, because of the

underthrusting of the cool ocean plate.

Idealized pattern of a back-arc basin

(form between an island-arc and

continent )

Idealized pattern of a fore-arc basin

(lie between the island-arc and the

ocean trench)

Fig: 34

• Indonesia provides a good example of these

subduction zone basins (Fig.35)

• Several back-arc basins have developed

behind the island-arc and adjacent to the

stable continental Sunda Shelf Smaller, arc basins are found in front of the island-arc Both types run parallel to the trench-arc

fore-system, where the northward-moving

Australian plate is being overridden by

EurAsia

Basins and tectonic elements of Indonesia

Fig: 35

•A cross section through the Sumatra back-arc and

Mentawai fore-arc basins illustrates the facies and

oil-productive at depths of less than a kilometer

Production comes from sandstone of Pliocene and late Miocene age, trapped in compaction structures over

the uneven basement topography and, higher in the

sequence, in anticlines Thick inter fingering and

overlying deepwater shales are the petroleum source.

In contrast, the fore-arc Mentawai basin

contains mostly shales and volcaniclastic

sediments, but also has thick carbonate banks and reefs (Seely and Dickinson, 1977) This

basin is relatively shallow, has a low heat flow, and is not commercially productive A major

reason for this is the lower-than-normal thermal gradient, caused by the descent of the cool

oceanic plate Also the volcaniclastic sediments

of fore-arc basins have poor porosities, when

compared to the more reworked back-arc

sands

Generalized cross-section through the Sumatra

(back-Fig: 36

• Non-arc basins are formed along convergent margins

where the plates move by transcurrent faulting

• Consequently, they are sometimes called strike-slip

basins They are also called California-type basins,

because they are common along the west coast of the United States

• Non-arc basins are small basins that form through a

combination of both the transcurrent fault movements and local block-faulting In addition to the California

basins, non-arc basins include the Vienna basin, and the Crimea and Baku basins of the Soviet Union

Idealized pattern of a Non-arc basin

Fig: 37

Fig: 39

Fig: 38

Fig: 40

• Collision basins, sometimes called median,

intermontane, or successor basins, are small basins formed within marginal fold-belts, along sutures where either two continents, or

continental coastal mountains and a trench,

have collided

Fig: 41

Fig: 42

Table 10.5 Convergent Margin Basins

A fore-arc B back-arc C non-arc (strike-slip, California-type)

D collision (median, intermontane, successor)

• Distinguishing features small, deep, young; local extension and

strike slip in regional compression along convergent plate margins.

• Depositional History immature, poorly sorted clastic sediments;

rapidly intertonguing facies; shallow to deep and/or volcanistic.

• Reservoir thick sandstones, often multiple; minor reefal

limestone.

• Source abundant, thick interbedded shale.

• Cap shale.

• Trap drape and compression anticlines, strike-slip and thrust

structures; reefs; horst-related combination

• Geothermal Gradient low (A); high (B,C); or normal to high (D)

• Hydrocarbons mostly paraffinic to paraffinic-naphthenic; variable

gravity; low natural gas

• Risks maturation; leakage; deformation too intense; igneous

activity; poor reservoir properties.

Downwarp Basin

Sedimentary basins that are downwarps into

small oceans are in a separate class, because

their sediments and petroleum characteristics are often very different from other basin types to

which they are genetically related,

- Open- related to pull-apart, passive margins

- Closed- related to foreland basins

- Trough- related to foreland basins

Fig: 43

Geometry of the world's downwarp basins

Fig: 44

Fig: 45

Generalized cross-section through the Gulf Coast basin, Southern USA and Gulf

of Mexico

Fig: 46

Fig: 47

Table 10.6 Downwarp Basin

into small oceans, inland seas or linear suture zones; intermediate crust.

unconformities.

paraffinic, carbonates more aromatic; average to high natural gas.

reservoir properties.

(C)

Tertiary Deltas

In a sense, tertiary-age deltas are not true

basins but later overprints onto other basin types They can form in any coastal setting, and are found about equally over convergent and divergent margins

Idealized pattern of a Tertiary age delta

Fig: 48

Fig: 49

94

Table 10.7 Tertiary Delta

triple junction where failed arm rift meets ocean basin,

particularly at divergent or transcurrent margin.

clastics with Type III kerogen.

Cap: shale.

lenses.

high natural gas.

developed.

• Type of past plate movement involved in

basin formation (divergent, convergent or

transform motion)

• Basin/cycle position on plate and primary

structural movement involved in basin

origination

Together the 25 sedimentary basins in the world, which are the richest in terms of known petroleum reserves , contain nearly 90% of the world's oil and gas

8-3-DISTRIBUTION OF PETROLEUM – RICH BASINS