GEOLOGY OF PETROLEUM SYSTEM

GEOLOGY OF PETROLEUM SYSTEM Dr. Dr Sugeng S Surjono Teknik Geologi FT UGM [email protected]

References

Petroleum Geology-2009

Baille, A.D., 1992, Sedimentary bain anlysis and

p petroleum occurence,, C Cource material off Program g Diklat Tim Pengelolaan IWPL-Migas Bekerjasama dengan IAGI Gluyas, J & Swarbrick, R., 2004, Petroleum geoscience, Blackwell Science Ltd, Oxford, 359p. Welte, D.H., Horsfield, B & Baker, D.R., 1997, Petroleum and basin evolution, Springer, Madras, 535p. 535p North, F.K., 1985, Petroleum geology, Allen & Unwin, London 607p London, 607p. Selley, R.C., 1998, Elements of petroleum geology, 2nd Academic Press, 2nd, Press San Diego, Diego 470p. 470p

Introduction


Petroleum geology is a branch of geology which is study petroleum in the earth from its geneneration up to exploitation.

The relationship of petroleum geology to the pure science (Selley, 1998)

Introduction


IIn the Petroleum Industry, Petroleum geology is only one aspect of petroleum th P t l I d t P t l l i l t f t l exploration and production.

(Selley, 1998)

Introduction L Level l off petroleum l iinvestigation i i


Sedimentary basin & Petroleum Systems


A sedimentary y basin is an area of the

earth’s crust that is underlain by a thick sequence of sedimentary rocks. Before acquiring acreage in a new area, it is y to establish the type yp of basin to necessary be evaluated and to consider what productive fairways p y it may y contain and where the may be extensively located. Other sciences needed for supporting pp g sedimentary basin study: regional geology, gy, g geophysics, p y , tectonics,, structural g stratigraphy-sedimentology

Petroleum System


A system where h hydrocarbon h d b is i allowed ll d to b be produced and accumulated within lithosphere 1. 1 2. 3 3. 4. 5.

Source Rocks Reservoir Rocks S l rocks Seal k Trapping mechanism Migration Pathways h & Time

Hydrocarbons commonly occur in sedimentary basins and are absent from intervening areas of igneous and metamorphic rocks (North (North, 1971)

Sedimentary Basin Analysis Scope of discussion: ¾ Plate Tectonic Approach ¾ Basin Setting ¾ Basin Formation ¾ Basin Fill ¾ Basin B i D Deformation f ti


Plate Tectonic Approach Crustal Types: à Continental Crust à Oceanic Crust

Plate Pl t Movement: M t à Convergence à Divergence à Strike-Slip

Global Tectonic Position: à Active Continental Margin à Passive Continental Margin


Plate Tectonic Approach Sedimentary basin form part of the earth’s crust. The Oceanic Th O i crustt is thin, dense and topographically low; Continental crust is thick, lower density y and higher elevation over the continent.


Plate Tectonic Appproach


Earth s crustal laterally move driven by convection cell in the Earth’s mantle. As a consequence; earth’s crust move each other.

Plate Tectonic Approach


earth’s earth s crust movement Earth’s crust is composed by a number of plates, where each plate were bounded by mid-oceanic mid oceanic ridges ridges, trenches and transform boundaries boundaries.

Plate boundary formed by plate movement: (A) Divergent, (B) Convergent; subduction, (C) Convergent margin (collision), (D) Transform fault margin.



earth’s earth s crust movement

Center of earthquake map : located in surrounding of plate boundaries



earth’s earth s crust movement

The lithosperic plates map showing a number a plates with types of plate boundaries

Plate Tectonic Approach earth’s earth s crust movement

The distributions of lithosperic plates in the world




Wilson cycle

The relative motion of p plates with

constructive, conservative and destructive plate margins creates a continually changing picture of continental splitting, ocean basin creation creation, ocean closure and continental collision. The Th cycle l off plate l motion i involving i l i the h birth and closure of ocean is termed “Wilson Cycle”. (Idea from John Tuzo Wilson, 1966)

Plate Tectonic Approach Wilson cycle The Wilson cycle of oceanic formation and closure: a. Continental extension b. Creation off a new oceanic spreading centre c. Ocean enlargement d. Subduction of oceanic floor fl (leads to closure oceanic basin) e. Subduction bd off oceanic ridge f. Continentcontinent collision ll


Plate Tectonic Approach Wilson cycle



Basin Setting g Continental Rifting à Syn-rift Syn rift à Post-rift

Island Arc Related à Fore Arc à Back Arc à Intra Arc

Passive Margin Related à Rift sequences à Passive margin sequences

Collision Zone à Rift sequences à Passive margin g sequences q à Collision sequence

Basin Setting Basin classification



Petroleum Geology-2009 Basin category

Continental or interior sag basins

Underlying crust

Style of tectonics

Basin characteristics

Continental

Divergence

Large areas, areas slow subsidence

Continental or interior fracture basins

Graben structures, rift valleys and rift zones, aulacogens

Continental

Divergence

Relatively narrow basins, faultbounded, rapid subsidence b id during d i early rifting

Basins on passive continental g , margin g margins, sag basin

Tensional-rifted basins, tensionsheared basins, sunk margin g basin

Transitional

Divergence + shear

Asymmetric basins partly outbuilding of sediment, moderate to low subsidence during later stage

Oceanic sag basins

Nascent ocean basin (growing oceanic-basins)

Oceanic

Divergence

Large, asymmetric, slow subsidence

Basins related to subduction

Deep-sea trenches Forearc basins, Backarc basins, Interarc basins

Oceanic

Convergence

Transitional, Oceanic

Dominantly divergence

Partly asymmetric, asymmetric greatly varying depth and subsidence

Remnant basins

Oceanic

Convergence

Activated subsidence d to rapid due id sedimentary loading

Foreland basins (Peri-pheral), retroarc basins ((intramontane), ), broken foreland basins

Continental

Crustal flexuring, local convergence g or transform motions

Asymmetric basins, trend to increasing subsidence, uplift and subsidence

Terrane-related basins

Oceanic

Pull-apart basins (trans-tensional) and transpressional basins

Continental and/or oceanic

Basins related to collision lli i

Strike-slip/ wrench basins

Einsele, 2000

Special basin type or synonym Epicontinental basins, intracratonic basins

Similar to backarc basins Transform motion + divergence or convergence

Relatively small, small elongated, rapid subsidence


Einsele, 2000


Basin Setting


Basin classification

Einsele, 2000

Basin Setting


Basin classification

Einsele, 2000


Basin Formation Extensional System Compressional p System y Strike-Slip System Basin Configuration Sedimentary Filling d ll Thermal Regime Maturity

Basin formation


basin related to stress field

Basin Geometries

Fault Types Rift Related Basin (Extensional Stress) Normal fault

Sedimentary Fill

Foreland Basin (Compressive Stress) Thrust fault Pull‐apart Basin (Lateral Stress) Wrench fault


DEPOSITIONAL ENVIRONMENT Correspond d to tectonic setting • Sedimentary basins are the subsiding areas where sediments

accumulate to form stratigraphic successions • The tectonic setting is the premier criterion to distinguish

different types of sedimentary basins • Extensional basins occur within or between plates and are

associated with increased heat flow due to hot mantle plumes • Collisional basins occur where plates collide, either characterized by subduction of an oceanic plate or continental collision • Transtensional basins occur where plates move in a strike-slip fashion relative to each other


DEPOSITIONAL ENVIRONMENT Correspond d to tectonic setting Extension • Rift basins develop in continental crust and constitute the

incipient extensional basin type; if the process continues it will ultimately lead to the development of an ocean basin flanked by passive margins, alternatively an intracratonic basin will form • Rift basins consist of a graben or half half-graben graben separated from surrounding horsts by normal faults; they can be filled with both continental and marine deposits • Intracratonic I t t i b basins i d develop l when h rifting ifti ceases, which hi h leads l d tto lithospheric cooling due to reduced heat flow; they are commonly large but not very deep


DEPOSITIONAL ENVIRONMENT Correspond d to tectonic setting Extension • Rift basins develop in continental crust and constitute the

incipient extensional basin type; if the process continues it will ultimately lead to the development of an ocean basin flanked by passive margins, alternatively an intracratonic basin will form • Rift basins consist of a graben or half half-graben graben separated from surrounding horsts by normal faults; they can be filled with both continental and marine deposits • Intracratonic I t t i b basins i d develop l when h rifting ifti ceases, which hi h leads l d tto lithospheric cooling due to reduced heat flow; they are commonly large but not very deep


DEPOSITIONAL ENVIRONMENT Correspond d to tectonic setting Extension • Proto-oceanic troughs form the transitional stage to the

development d l off llarge ocean b basins, i and d are underlain d l i b by incipient oceanic crust • Passive margins develop on continental margins along the edges

of ocean basins; subsidence is caused by lithospheric cooling and sediment loading, and depending on the environmental setting clastic or carbonate facies may dominate • Ocean basins are dominated by pelagic deposition (biogenic

material and clays) in the central parts and turbidites along the margins


DEPOSITIONAL ENVIRONMENT Correspond d to tectonic setting Collision • Subduction is a common process at active margins where plates

collide llid and d at lleast one oceanic i plate l iis iinvolved; l d severall types off sedimentary basins can be formed due to subduction, including trench basins, forearc basins, backarc basins, and retroarc foreland basins • Trench basins can be very deep, and the sedimentary fill depends

primarily on whether they are intra-oceanic intra oceanic or proximal to a continent • Accretionary prisms are ocean sediments that are scraped off the

subducting plate; they sometimes form island chains


DEPOSITIONAL ENVIRONMENT Correspond d to tectonic setting Collision • Forearc basins form between the accretionary prism and the

volcanic l i arc and d subside b id entirely i l d due to sediment di lloading; di lik like trench basins, their fill depends strongly on whether they are intra-oceanic or proximal to a continent • Backarc basins are extensional basins that may form on the

overriding plate, behind the volcanic arc • Retroarc R t fforeland l db basins i fform as a result lt off lithospheric lith h i loading l di

behind a mountainous arc under a compressional regime; they are commonly filled with continental deposits


DEPOSITIONAL ENVIRONMENT Correspond d to tectonic setting Collision • Continental collision leads to the creation of orogenic (mountain)

belts; b l li lithospheric h h i loading l di causes the h d development l off peripheral i h l foreland basins, which typically exhibit a fill from deep marine through shallow marine to continental deposits • Foreland basins can accumulate exceptionally thick (~10 km)

stratigraphic successions


DEPOSITIONAL ENVIRONMENT Correspond d to tectonic setting Transtension • Strike-slip basins form in transtensional regimes and are usually

relatively l i l small ll b but also l d deep; they h are commonly l fill filled d with ih coarse facies (e.g., alluvial fans) adjacent to lacustrine or marine deposits

Basin Filling Depositional Environment


Basin Filling Depositional Environment


Depositional Environment


Fluvial environments Bedrock rivers essentially do not contribute to the stratigraphic

record, d contrary t tto alluvial ll i l rivers i

Alluvial fans are relatively steep (>1 (>1-2°) 2°) cones consisting of coarsecoarse

grained facies and constitute the most proximal fluvial depositional environments (usually at the break of slope on the edge of a floodplain) • Debris flows dominate on small and steep alluvial fans • Sheetfloods are common on larger and gentler alluvial fans

Depositional Environment Fluvial environments

Channel patterns (fluvial styles) are

commonly classified as: • • • •

Braided rivers Meandering rivers Straight rivers Anastomosing rivers




Fluvial environments Bars are sandy or gravelly macroforms in channels that are emergent,

mostly tl unvegetated t t d ffeatures t att llow fl flow stage, t and d undergo d submergence and rapid modification during high discharge

Point bars form on inner banks and typically accrete laterally,

commonly resulting in lateral-accretion surfaces; mid-channel or braid bars accrete both laterally and downstream

Braided B id d rivers i are characterized h t i d by b a dominance d i off braid b id bars; b

meandering rivers primarily contain point bars; in straight (and most anastomosing) rivers bars are almost absent



Fluvial environments Channel belts consist of channel-bar and channel-fill deposits;

the proportion th ti off the th two t generally ll d decreases markedly k dl from f braided b id d rivers to straight or anastomosing rivers

The geometry of a channel belt (width/thickness ratio) is a function of

the channel width and the degree of lateral migration; values are typically much higher for braided systems (>>100) than for straight or anastomosing systems (<25)

Residual-channel deposits are predominantly muddy (occasionally

organic) deposits that accumulate in an abandoned channel where flow velocities are extremely small



Fluvial environments Overbank environments are dominated by fine-grained facies

(predominantly muds)

• Natural-levee deposits are wedges of sediment that form adjacent to the

channel, dominated by fine sand and silt exhibiting planar stratification or ((climbing) g) ripple pp cross stratification • Crevasse-splay deposits are usually cones of sandy to silty facies with both coarsening-upward and fining-upward successions, and are formed by small, secondary channels during peak flow • Flood-basin deposits are the most distal facies, consisting entirely of sediments deposited from suspension, and are volumetrically very important (mainly in low-energy fluvial settings)

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Fluvial environments Paleosols (well drained conditions) and peats (poorly drained

conditions) diti ) occur ffrequently tl iin overbank b k environments i t and d are important indicators of variations of clastic aggradation rates and the position relative to active channels

Lacustrine deposits can be important in overbank environments

characterized by high water tables, and are also found in distal settings



Fluvial environments Facies successions in sandy to gravelly channel deposits typically fine

upward, d from f a coarse channel h l lag, l through th h large-scale l l to t small-scale ll l cross stratified sets (commonly with decreasing set height), and finally overlain by muddy overbank deposits

Facies successions produced by different fluvial styles can be extremely

similar!

The Th geometry t and d three-dimensional th di i l arrangementt off architectural hit t l

elements therefore provides a much better means of inferring fluvial styles from the sedimentary record



Fluvial environments Avulsion is the sudden diversion of a channel to a new location on the

floodplain, fl d l i leading l di to t the th abandonment b d t off a channel h l belt b lt and d the th initiation of a new one

Alluvial architecture refers to the three-dimensional three dimensional arrangement of

channel-belt deposits and overbank deposits in a fluvial succession

The nature of alluvial architecture (e.g., the proportion of channel-belt

tto overbank b kd deposits) it ) is i dependent d d t on fluvial fl i l style, t l aggradation d ti rate, t and the frequency of avulsion



Fluvial environments Avulsion is the sudden diversion of a channel to a new location on the

floodplain, fl d l i leading l di to t the th abandonment b d t off a channel h l belt b lt and d the th initiation of a new one

Alluvial architecture refers to the three-dimensional three dimensional arrangement of

channel-belt deposits and overbank deposits in a fluvial succession

The nature of alluvial architecture (e.g., the proportion of channel-belt

tto overbank b kd deposits) it ) is i dependent d d t on fluvial fl i l style, t l aggradation d ti rate, t and the frequency of avulsion



Deltaic environments Deltas form where a river enters a standing body of water (ocean, sea,

lake) and forms a thick deposit that may or may not form protuberances The delta plain is the subaerial part of a delta (gradational upstream to a floodplain); the delta front (delta slope and prodelta) is the subaqueous component Delta plains are commonly characterized by distributaries and flood b i (upper basins ( delta d lt plain) l i ) or interdistributary i t di t ib t bays b (lower (l delta d lt plain), l i ) as well as numerous crevasse splays Upper delta plains contain facies assemblages that are very similar to fluvial settings



Deltaic environments Mouth bars form at the upper edge of the delta front, at the mouth of

di t ib t i distributaries; they th are mostly tl sandy d and d tend t d to t coarsen upwards d

The delta slope is commonly 1-2° and consists of finer (usually silty)

facies; the most distal prodelta is dominated by even finer sediment

Progradation (basinward building) of deltas leads to coarsening-upward

successions, and progradation rates depend on sediment supply and b i bathymetry basin b th t (water ( t depth) d th)



Deltaic environments Delta morphology reflects the relative importance of fluvial, tidal, and

wave processes processes, as well as gradient and sediment supply

• River-dominated deltas occur in microtidal settings with limited wave

energy, where delta-lobe progradation is significant and redistribution of mouth bars is limited • Wave-dominated deltas are characterized by mouth bars reworked into shore-parallel sand bodies and beaches • Tide-dominated deltas exhibit tidal mudflats and mouth bars that are reworked into elongate sand bodies perpendicular to the shoreline



Deltaic environments Coarse-grained deltas are composed of gravelly facies and form where

alluvial ll i l ffans or relatively l ti l steep t braided b id d rivers i enter t a water t body b d

Delta cycles are the result of repetitive switching of delta lobes,

comparable to avulsion in fluvial environments; this leads to characteristic vertical successions with progradational facies and transgressive facies



Deltaic environments Coarse-grained deltas are composed of gravelly facies and form where

alluvial ll i l ffans or relatively l ti l steep t braided b id d rivers i enter t a water t body b d

Delta cycles are the result of repetitive switching of delta lobes,

comparable to avulsion in fluvial environments; this leads to characteristic vertical successions with progradational facies and transgressive facies



Coastal environments Erosional coasts are commonly characterized by cliffs, whereas

constructional t ti l coasts t can b be fformed db by clastic, l ti carbonate, b t or evaporite it facies

The morphology of constructional coasts is determined by sediment

supply, wave energy, and tidal range, as well as climate and sea-level history



Coastal environments Beaches form when sand or gravel is available and wave energy is

significant, i ifi t and d result lt in i low-angle l l cross-stratified t tifi d d deposits it and d cross strata formed by wave ripples

Beaches can either be connected directly to the land and form strand

plains or chenier plains (the latter consisting of beach ridges separated by muds), or be separated by lagoons or tidal basins (the latter consisting of tidal channels, channels tidal flats, flats and salt marshes) and form either spits or barrier islands



Coastal environments Beaches form when sand or gravel is available and wave energy is

significant, i ifi t and d result lt in i low-angle l l cross-stratified t tifi d d deposits it and d cross strata formed by wave ripples

Beaches can either be connected directly to the land and form strand

plains or chenier plains (the latter consisting of beach ridges separated by muds), or be separated by lagoons or tidal basins (the latter consisting of tidal channels, channels tidal flats, flats and salt marshes) and form either spits or barrier islands



Coastal environments Barrier islands are especially prolific in environments with a high wave

energy and d a limited li it d tidal tid l range, that th t have h experienced i d transgression t i (relative sea-level rise)

The tidal inlets between barrier islands are sites of deep erosional scour

and are associated with flood-tidal deltas (lagoonal side) and ebb-tidal deltas (seaward side)

Washovers W h can form f during d i major j storm t events, t and d are found f d

elsewhere across barrier islands

Coastal dunes are common features associated with sandy y beaches



Coastal environments Estuaries are semi-enclosed coastal water bodies where fluvial and

marine i processes interact i t t

• Tide-dominated estuaries have tidal channels with bars and tidal

mudflats that contain tidal sedimentary structures (e.g., tidal bundles, heterolithic stratification) • Wave-dominated estuaries are partly enclosed by a coastal barrier and have well-developed bay-head deltas



Coastal environments Carbonate coastal environments can exhibit comparable characteristics

as clastic l ti coasts t (i.e., (i barriers b i and d lagoons), l ) consisting i ti off carbonate b t sands and muds, respectively

• Stromatolites (algal or bacterial mats) commonly form on carbonate-rich

tidal flats

Arid A id coastal t l environments i t are characterized h t i d by b sabkhas bkh and d salinas, li

coastal plains frequently inundated by saline water and hypersaline lagoons, respectively, where evaporites (notably anhydrite and gypsum) can accumulate



Shallow marine environments Shallow seas can be subdivided into clastic and carbonate-dominated

systems, t d depending di mainly i l on sediment di t supply l and d climatic li ti setting tti

Idealized models predict a general decrease of grain size with water

depth (i.e., away from the shoreline); however, this simple picture is complicated by a large number of factors (e.g., shelf bathymetry)



Shallow marine environments Storm-dominated clastic shelves ideally exhibit a transition from

predominantly wave wave-rippled rippled sands in the upper shoreface, shoreface to alternating sands and muds (tempestites with hummocky cross stratification) in the lower shoreface, to muddy facies below storm wave base Tide-dominated clastic shelves may exhibit erosional features, features sand ribbons, and sand waves with decreasing flow velocities, commonly associated with mud-draped subaqueous dunes; tidal sand ridges (tens of m high high, many km across) are characteristic of shelves with a high supply of sand Bioturbation can obliterate many primary sedimentary structures in shelf environments



Shallow marine environments Shallow seas within the photic zone are the premier ‘carbonate

f t i ’ factories’

Carbonate platforms can cover continental shelves or epicontinental

seas, when the conditions for carbonate production (temperature, salinity, light conditions) are favorable

Isolated platforms (atolls) are found in shallow seas surrounded by

d deep water, t lik like extinct ti t volcanoes l



Shallow marine environments Carbonate ramps exhibit processes and characteristics comparable to

clastic l ti shelves, h l with ith carbonate b t sands d and d muds d ultimately lti t l producing d i a seaward transition from grainstone to mudstone, commonly with similar sedimentary structures

Rimmed carbonate shelves consist of a coral reef or carbonate sand

barrier at some distance from the mainland; the shelf lagoon can be up to many tens of kilometers wide • Boundstones dominate the reef facies • Shelf lagoon facies are mostly fine-grained and ultimately lead to the

f formation ti off mudstones d t and d wackestones k t



Deep marine environments The continental slope is a major source of sediment for the deep sea,

and d is i a setting tti where h slumps l can occur

Debris flows and turbidity currents are the main mechanisms of

transport from the continental slope into the deep sea; these processes can be triggered by external forcing (e.g., an earthquake) or by the slope reaching a critical state as a result of ongoing deposition

Debris-flow D b i fl deposits d it and d turbidites t bidit are often ft genetically ti ll related l t d Turbidites can be both clastic (commonly leading to the formation of

wackes)) or calcareous

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Deep marine environments Submarine canyons at the shelf edge (commonly related to deltas) are

connected to submarine fans on the ocean floor Contrary to debris flows, turbidites exhibit a distinct proximal to distal fining Submarine S b i fans f share h severall characteristics h i i with i h deltas; d l they h consist i off a feeder channel that divides into numerous distributary channels bordered by natural levees and are subject to avulsions • Proximal fan (trunk channel) • Medial fan (lobes) • Distal fan

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Deep marine environments Basal Bouma-divisions have the highest preservation potential updip;

upper Bouma-divisions B di i i are more common downdip d di

Turbidite lobes characterize the medial fan and may exhibit the most

complete Bouma sequences

The Bouma-model is increasingly challenged, because many turbidites

do not conform to it (e.g., ‘high-concentration turbidites’)

Contourites are formed by ocean currents and commonly represent

reworked turbidites



Deep marine environments Pelagic sediments primarily have a biogenic origin • Calcareous ooze (e.g., (e g foraminifera) forms above the calcite compensation

depth (CCD) at ~4000 m depth • Siliceous ooze (e.g., radiolarians, diatoms) forms between the CCD and ~6000 6000 m depth where silica dissolves; it lithifies into cherts

Hemipelagic sediments consist of fine-grained (muddy) terrigenous

material that is deposited from suspension

• Eolian dust is an important component (~50%) of hemipelagic (and pelagic)

facies • Black shales have a 1-15% organic-matter content and form in anoxic bottom waters


Basin Filling g Accomodation Space à Eustatic à Tectonic

Sediment S di tS Supply l à Tectonic à Climate

Progradation Retrogradation Agradation

Depositional Setting à Continental à Transitional à Marine

Source Rock Distribution Source Rock Types Kitchen Area Reservoir Distribution R Reservoir Quality i Q lit

Basin Filling Accommodation space


Basin Filling


Regional Stratigraphy Regional g stratigraphic g p succession Source rock potential Reservoir potential

Basin evolution Source rock and reservoir potential


Schematic illustration of the relationship and difference between accommodation and paleobathimetry.

Petroleum System Source Rocks Reservoir Rocks Seal rocks Trapping mechanism Migration Pathways & Time



Petroleum System Diagram


Petroleum System





GEOLOGY OF PETROLEUM SYSTEM

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