carbon carbon carbon.ppt

8/10/2019 Carbon carbon carbon.ppt

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Carbonate Definition

Karbonat adalah senyawa yang terdiri dari partikel biogenic dan

unsur kimia kalsit (CaCO3) dengan properti reservoar berbeda

untuk setiap sorting ukuran butir dan diagenesis yang berbeda

Terbentuk secara alami sebagai sedimen pada reefs di lautantropical modern

Terdiri atas mineral : Low Mg calcite, High Mg calcite & Aragonite.

Karbonat adalah anionic complexes dari CO3 dan divalen metallic

cation seperti Ca, Mg,


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karbonat terbentuk dari sisasisa jasad renik binatang dan/atau

tumbuhan (shellfish dan algae)

umumnya karbonat ditemukan dekat dengan tempat asal

pembentukannya, tanpa ditransportasikan dan diendapkan sepertibatuan pasir

kalsium karbonat sebagai bagian inti dari karbonat dapat

dengan mudah terlarutkan oleh air, sehingga sangat mungkin

terjadi pelarutan dan kristalisasi kembali (recrystallization)

setelah batuan ini terbentuk. Pelarutan ini mengakibatkan terbentuknya kavitasi sehingga

dapat menyimpan minyak dalam jumlah yang banyak. Selain

itu, karena sifat batuan karbonat yang lebih rentan (brittle)

terhadap patahan dan pelipatan, dibandingkan dengan

sandstone, maka akan memungkinkan terbentuknya rekahan(fractures) yang dapat sebagai jalan untuk mengalirkan fluida

reservoir (minyak, gas, atau air).


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A carbonate platformis a sedimentary body whichpossesses topographic relief, and is composed of autochthonouscalcareous deposits (Wilson, 1975)

Platform growth is mediated by sessile organismswhose skeletons build up the reef or by organisms(usually microbes) which induce carbonate precipitation throughtheir metabolism.

limiting factors are, amongothers: light, water temperature, transparency and pH-Value


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Carbonate Platform

Classification Several factors influence the geometry of a carbonate platform, including

inherited topography, synsedimentary tectonics, exposition to currentsand trade winds. However, the one most important factor is perhaps thetype of carbonate factory

A carbonate factory is the ensemble of the sedimentary environment, theintervening organisms and the precipitation processes that lead to the

formation of a carbonate platform (Schlager, 2005).

Tropical factory

In these platforms precipitation is biotically controlled, mostlyby autotrophic organisms. Organisms that build this kind of platform aremostly corals, green algae,

foraminifer and molluscs. These platforms arefound only in warm (more than 20C) and sunlit waters, high in oxygen and

low in nutrients. This means that they are found between 30north and 30south of the equator. This type of factory is the most widespread today, andis often found fossilised.


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Cool-water factory

As the name suggests, this type of platform extends its domain tocooler waters and higher latitudes than tropical factories.Precipitation is biotically controlled by heterotrophic organisms,

sometimes in association with photo-autotrophic organisms suchas red algae. The sea-waters of these platforms are characterisedby a higher amount of nutrients than in tropical factories.

Mud-mound factory

These platforms are characterised by abiotic precipitation andbiotically induced precipitation. They grow in waters highin nutrients and low in oxygen. Mud-mound factories are known onlyfrom the fossil record, especially Palaeozoic and Mesozoic.


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Cool-water factories tend to

generate ramps

Tropical factories usually form high-

relief rimmed platforms and mud-

mounds, mound-shaped high relief

bodies without a clear zone of dip

break

Tropical carbonate platforms can be

subdivided into three principal

sedimentary environments: reef,

internal lagoon and slope
http://en.wikipedia.org/w/index.php?title=Carbonate_ramp&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Mud-mound&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Mud-mound&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Mud-mound&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Mud-mound&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Mud-mound&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Carbonate_ramp&action=edit&redlink=1


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The reef is that part of a carbonate platform created by essentially

in-place, sessile organisms. Todays reefs are built

by hermatypic organisms. The reef is the rigid structure of carbonate

platforms and is located between the internal lagoon and the slope.

Survival of the platform depends on the existence of the reef,because only this part of the platform can build a rigid, wave-

resistant structure. Two reef types are distinguished: isolated

(detached) or epicontinental (attached / barrier island) Geologically

speaking, reef rocks can be classified as massive boundstones.

Reefs are held up by a macroscopic skeletal framework. Coral reefs

are an excellent example of this kind. Corals and calcareous algae

grow on top of one another and form a three-dimensional framework

that is modified in various ways by other organisms and inorganic

processes.


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Lagoonis the part of platform behind the reef. It is characterised by

shallow and calm waters. Sediments are composed of reef

fragments and hard parts of organisms. If the reef is epicontinental

there can be also a terrigenous contribution. In some lagoons (e.g.,

the Florida Bay) green algae produce great volumes of carbonatemud. Rocks here are mudstones to grainstonesdepending on

the energy of the environment.


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Carbonate Properties

Texture-Ukuran, bentuk, sorting butir batuan di batuan sedimen (Pettijohn, 1975)

Grain type

-Dunham (1962), grain supported cenderung memiliki porositas lebih darimud supported

Sedimentary structures-Merujuk ke bedform yang terbentuk akibat fluid process pada interfacesediment

Fabric

-Pengaturan ruang dan orientasi butiran di batuan sedimen

Mineral composition

-Menunjuk kepada original mineralogy


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Texture (Grain Sizes)


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Fabric

Proses deposional, diagenetic, biogenic membuat fabric batuan reservoar

Depositional fabric is the spatial orientation and alignment of grains

in a detrital rock

Fabric affect reservoir porosity and can impart directional permeability,

ultimately affecting reservoir performance characteristics

presence or absence of depositional fabric is easily determined with coresamples, homever, determination of directional azimuth requires oriented cores

Diagenetic fabris include patterns of crystal growth formed during cementation,

recrystallization, or replacement of carbonate sediments and fabrics formed by

dissolution

Biogenic Fabrics are describeb in connection with carbonate buildups, or reefs

and with the internal micrstructure of skeletal grains


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Dissolution fabrics include a wide rang of features such as molds, , caverns

karst features, and soils. The size, shape, orientation and crystal "packing" (disposition of the crystal

faces with respect to each other) create an internal fabric that greatly

affects reservoir connectivity because they determine th size, shape and distri

bution of pores and connecting pore throats


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Composition

Komposisi karbonat lebih merujuk kepada jenis butir batuan dibandingkan jenismineral

NonSkeletal grain: Ooid, Peloid, aggregate, clast

>ooid: coated grain with calcareous cortex and nucleus which variable in composition

>peloid: size 100-500 m, composed of microcrystaline carbonate, rounded-subrounded, spherical, ellipsoidal to irregular, origins from: pellets, calcareous algae,micritised grain, mudclast.

>aggregate: several carbonate particles become bound & cemented together.>clast: represet reworked fragment of at least partly consolidated carbonatesedmient.

Skeletal grain: organism poduct of calcareous skeleton, most inherent instabilityduring diagenesis result in unstable minerals: aragonite and hi-Mg calcite

Noncarbonate detritus


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Sedimentary Structure

Struktur sedimen adalah alat bantu intrepetasi depositional

environment

Struktur sedimen bisa mempengaruhi karakteristik reservoar karena

fabric internalnya pada umumnya ber orientasi dan ada pola

perubahan ukuran butir pada struktur sedimen


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Carbonate Process

Deposition Process

Combination of process: Physical

Chemical

Biological

Physical process Temperature 2030C

Light: varies with water clarity and depth

Bathymetry: Shallow enough for warm temp & light

Clarity: No turbidity to block light & affect filter feeders

Circulation: Needed for nutrient supply Energy: Tides, waves currents, suspension transport; can vary from

low to high; results in variation in organisms and sediment type


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Chemical process

Salinity: Normal marine

Nutrients: Steady supply

Saturation: Dependent on temperature, pressure, salinity andconcentration of Ca and CO3

Cementation: Stabilizes sediments

Biological process

Growth rates: Faster growth produces more sediment

Growth form: Different growth forms produce different types of

sediment Mineralogy: Aragonite and hi-Mg calcite skeletons are more soluble

Organic binding: Reefs, algal coatings, algal mats stabilizesediments

Baffling: Sessile fauna and flora (sea grasses) stabilize sediments

Bioturbation: Organisms burrowing through sediment homogenize it Pelleting: Organisms convert mud to grains by passing through gut


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Carbonate Depositional

Environment It is the interaction of the oceanic hydrological regime with platform

geomorphology that determines the anatomy of the depositionalfacies on the platforms, the location of the facies on the platforms,and the rock types exhibited in the facies.

Unbroken slopes from shore to open sea are swept by open oceanwaves and currents; those with slope breaks occurring within fair -

weather wave base will have high - energy facies at the slopebreak and restricted circulation behind it.


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Ramp

Carbonate ramps are carbonate

platforms which have a very low

gradient depositional slope

(commonly less than 0.1 ~ from a

shallow-water shoreline or lagoon

to a basin floor (Burchette &Wright 1992)


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Beach-Dune

Batas laut dan mainland atau laut dan lagoon

Attached = Batas laut dan mainland

Detached / Barrier island = batas laut dan lagoon

Dune pada umumnya ada di updip pantai tapi bisa tidak ada jikasupply sedimen tidak cukup atau tidak ada arus angin yang cukupkuat

Environment ini terbagi menjadi 3 subdivisions : lower, middle(transition), upper shoreface


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Formation of Dolomite and Limestone

Limestone and dolomite are formed by an accumulation of sediments.Thebest sources of dolomite formations are in magnesium rich ground waterswith a high salinity; for example, dolomite is formed in highly saline lakes inthe Coorong region in South Australia. Laboratory tests suggest thatdolomite needs temperatures above 212 F to form. Yet it is unclear howexactly dolomite is formed. Limestone is formed of remains of tiny shellscoral, algal, fecal debris and microskeletons, which are deposited on theseabed. The shells and skeletons are compressed to form solid rock.Limestone is formed in layers and contains vertical cracks. The layers andthe cracks make the rock permeable, allowing water to flow through. Waterdripping from the roofs of limestone caves can leave behind particles andform icicle-shaped stalactites. Water that drips onto the floor of caves can

lead to the formation of stalagmites.

Characteristics

Dolomite has a pearly luster. Colorless and white dolomite is common, butyou can find yellow, gray, brown and black dolomite. Black dolomiteindicates the presence of iron in the crystals. High manganese contentgives dolomite crystals a pink color. Limestone is often light gray, and thereare often streaks, fossils or shell formations in the stone. The shells andfossils mean that it has a high concentration of calcium.


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**Dolomitizationis a process by which dolomiteis formed

when magnesiumionsreplace calciumions in calcite. It is common

for this mineral alterationinto dolomite to take place due to

evaporation of water in the sabkhaarea
http://en.wikipedia.org/wiki/Dolomitehttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Calcitehttp://en.wikipedia.org/wiki/Mineral_alterationhttp://en.wikipedia.org/wiki/Sabkhahttp://en.wikipedia.org/wiki/Sabkhahttp://en.wikipedia.org/wiki/Mineral_alterationhttp://en.wikipedia.org/wiki/Calcitehttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Dolomite


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Porositas Karbonat


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carbon carbon carbon.ppt

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