Mg-6 Karbonat

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BATUAN KARBONATKRISTIAN N TABRI

Appl ied Geolog y Research Div is ion

Faculty o f Earth Science and Technolog y

Ins t it u t Tekno log i Bandung

2011


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Geologic Aspects of CarbonateReservoirs: General Introduction: Concept of carbonates and carbonate

deposition

Carbonate Rock Types: Characteristics, Classification and Origin ofCarbonate Rocks

Carbonate Rock Resevoir Geometry: concepts of carbonate

platforms, build-ups, reefs and banks and sequence of stratigraphy Carbonate Sedimentation, Diagenesis and Dolomitization.

Carbonate Porosity Types, Classification (Choquette and Pray,1976), Characteristics, heterogenity and Origin.

Exploration concepts, strategy and tactics and development ofcarbonate plays

Geologic modeling of carbonate reservoirs using seismic, well logs(sample log, wireline logs, FMI etc), cores biostratigraphic and otherdata.


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GENERAL INTRODUCTION


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GENERAL INTRODUCTION:

Concept of carbonate rocks and

Concept of carbonate

deposition


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CONCEPT OF CARBONATE ROCKS

CARBONATE ROCKS OF CARBONATES ARESEDIMENTARY ROCKS WHICH CONSISTS OFCARBONATE MINERALS.

THEY COMPRISE OF LIMESTONESANDDOLOSTONES (DOLOMITES). CARBONATE ROCKS ARE PRACTICALLY

MONOMINERALIC CONSISTING OF CALCIUMCARBONATE MINERALS WITH FEW INSERTION OFMAGNESIUM IN THE CRYSTAL LATTICE.

CARBONATES ARE CHARACTERIZED ANDDIFFERENTIATED BY ITS FABRIC AND TEXTURERATHER THAN BY ITS MINERAL COMPOSITION.


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CHARACTERISTICS OF

CARBONATE ROCKS

CARBONATE ROCKS COMPRISES LESSTHAN 30% OF THE STRATIGRAPHICSECTION.

WIDE-SPREAD CARBONATE ROCKSINDICATE A SPECIAL TECTONIC CONDITION:TECTONIC QUISCENCE.

CARBONATE ROCKS ALSO INDICATE ASPECIAL DEPOSITIONAL ENVIRONMENT:CLEAR, WARM AND GENERALLY SHALLOWMARINE DEPOSIT.


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LIMESTONE IN RELATION TO SILICI-

CLASTICS


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LIMESTONE

MARL

RELATIONSHIP

The term marl is not usedin the petroleum industry or

American literature, the

term calcareous shale is

used instead.

Marl is used as a special

term for lacustrine shales


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CARBONATE SEDIMENTATION

CARBONATE SEDIMENTATION IS CONTROLLED BY A SINGLECHEMICAL EQUILIBRIUM EQUATION:

H+ + HCO3- + Ca2+ CaCO3 + H2O + CO2Increase of CO2 concentration in the solution will shift the equation to the

left, resulting dissolution of the calcium carbonates.

Increase of CO2 concentration may due to increasing depth (PCO2)

Input of meteoric water or input of CO2 due decay of organic materila

Decreas of CO2 concentration will shift the equation to the right, resultinginto carbonate deposition

Decrease of CO2 concentration may be due to:

Evaporation, increase of temperature due heating of the sea water by the

sun, escpecially in shallow waters

CO2 capture by organism, especially algae for photo-synthesis


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CHEMICAL CONTROLS OF


DEPOSITION AND DISSOLUTION ARE CONTROLLEDBY Concentrations of Ca ++ ions

Concentrations of CO3

ions SATURATION OF Ca ++ IONS IS CONTROLLED BY

Evaporation and

Temperature

SATURATION OF CO4 IONS IS CONTROLLED BY

PARTIAL PRESSURE, Temperature,

Atmospheric and

Biogenic activities/ particularly photosynthesis.


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CARBONATE CHEMICAL

ENVIRONMENT OF DEPOSITON

CARBONATES ARE DEPOSITED IN

HIGH Ph SALINE ENVIRONMENT.

CARBONATES ARE GENERALLYDEPOSITED IN MARINE

ENVIRONMENT.

SOME CARBONATES ARE ALSODEPOSITED IN LACUSTRINE SALINE

ENVIRONMENT.


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CARBONATE COMPENSATION

DEPTH

IN OCEANS: Partial pressure of CO2 increases with depth.

Temperature decreases with depth.

HENCE: Solubility of carbonate minerals (arragonite and

calcite) increases with depth.

CARBONATE MINERALS ARE DISSOLVED AT

CERTAIN DEPTH CALLED RESPECTIVELY : Arragonite Compensation Depth (ACD)

Calcite Compensation Depth (CCD)


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CARBONATE DEPOSITONAL

ENVIRONMENTS

Carbonates are generally warm water

sediments.

Carbonates are generally shallow water

sediments; deep water carbonates are

restricted to pelagic limestones.

Carbonates are generally deposited in

clear marine waters, free of fine clastics


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GEOCHEMICAL CYCLE OF

CARBON ATES


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WORLD WIDE DISTRIBUTION OF



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WET TROPICAL AREAS COINCIDING WITH WITH

REGIONS OF ABUNDANCE OF SILICICLASTIC INPUT


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DEPTH DISTRIBUTION OF



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CARBONATE

COMPENSATION

DEPTHragonite

Calcite

Isocline

ACD

ATLANTIC OCEAN

Degree of Saturation

D

e

p

th

I

n

Km

CCD


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SEDIMENTARY PROCESSES OF

CARBONATES


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PROCESSES OF CARBONATE

DEPOSITION

SECRETION - SKELETAL COMPONENTS

ACCRETION NON-SKELETAL COMPONENTS AGREGATION- SKELETAL & NON-SKELETAL

PARTICULATION NON-SKELETAL

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Mg-6 Karbonat

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