seismik stratigrafi migas

5/28/2018 Seismik Stratigrafi MIGAS

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SEISMIC

STRATIGRAPHY


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Angular unconformity is usedwhen layers below are clearlytilted or folded and then eroded

before deposition continues on theeroded surface

Disconformity is used whenbeds above and below areparallel but a well-developederosional surface can berecognized, by irregular

incision, soil development, orbasal gravel deposits on top.

Paraconformity is used forobscure unconformities wherecorrelation with time markerselsewhere indicates missingstrata, even though no

evidence of a gap is presentlocally.

Nonconformity is used fordeposition of bedded strata onunbedded (usually igneous ormetamorphic) basement.

KlasikUnconformity


3/34Eni IndonesiaSeismic Stratigraphy, Vail et al., 1977


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Definisi

Seismik Fasies adalah unit atau paket pola-pola refleksi yangteramati pada sekuen seismik.

Hubungan perlapisan dengan refleksi terminasi:

Toplap : refleksi terminasi yang menumpu ke arah

permukaan erosi yang berada di atasnya/ hiatus.

Onlap : refleksi terminasi yang menumpu ke permukaan

miring (maju ke depan).

Downlap(berada di bagian bawah): refleksi terminasi miring

yang menumpu ke permukaan horisontal/miring.


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Stratal Termination

onlap

downlap

onlap

Sequence

Boundary (SB)

Erosional

Truncation

Sequence

Boundary (SB)

Downlap

Surface

toplap

Apparent

Truncation


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Asosiasi Seimik Fasies

(Mitchum et al., 1977)

Basin Slope Intraslope Basin Shelf

External Form mound sheet drape chaotic basin-fill slope front fill wedge tabularInternalconfiguration

hummocky concordant chaotic-

hummockyclinoform divergent concordant

ReflectionContinuity

discontinuous continuous discontinuous continuous continuous continuous

ReflectionAmplitude variable

moderate

to highvariable

moderate

to highmoderate

moderate

to high

Upper ReflectionTerminations onlap concordant

apparenttruncations&onlap toplap

toplap &truncation local toplap

Lower Reflection

Terminations

bidirectional

downlapsome onlap random downlap downlap downlap local downlap

Physiographic

Areal/ Seismic

Refelction

Characters

Slope/shelf Break


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High

Moderate

Low

Continuous

Discontinuous

Variable

Parallel

Angular

Lenticular

Contorted

Hummocky

Chaotic

Clinoform

Regular Migrating

Irregular

Horizontal

Inclined

Undulating

Divergent/Convergent

Sub-parallel

Discordant

Reflection Free

INTERNAL REFLECTION

CHARACTER

CONFIGURATION

REFLECTION

REFLECTIONCONTINUITY

REFLECTION

AMPLITUDE


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Reflection Configuration: Paralel & Subparalel

REGULAR MIGRATING

IRREGULAR

SUBPARALLEL

HORIZONTAL

UNDULATING

INCLINED

PARALLEL


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Parallel & Sub-Parallel

Parallel and Sub-Parallel : Stable basin plain,

Subsiding shelf: Even & Wavy

Divergent : variation in the rate of deposition,

progressive tilting of depositional surface


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Reflection Configuration: Clinoform

SIGMOID

OBLIQUE

SHINGLED

PARALLEL

CLINOFORM


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Clinoform

Sigmoid : low sediment suplay, relatively

rapid subsidence, rapid rise in sea level.

Oblique : progradation pattern, small channel-

fill configurations.

Shingled : prograding into shallow water

Parallel : progradation pattern


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LENTICULARANGULAR CONTORTED

CHAOTICHUMMOCKY

DISCORDANT

Reflection Configuration: Discordant


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Discordant

Hummocky : pro delta, inter-delta; shallow

marine

Chaotic : slump structure, cut-and-fill channel

complexes, highly faulted, folded, contorted

zones

Contorted : slump structure

Angular & Lenticular : Large cross bedding


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Reflection free

Homogeneous shales, sanndstone etc.,

Nonstratified

Highly contorted Steeply dipping lithologic unit

Large igneous masses

Salt features


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Reflection Configuration

FREE/ TRANSPARENT

DIVERGENT/CONVERGENT

CONTINUOUSDISCONTINUOUS DISCONTINUOUS

REFLECTION CONTINUITY


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Geometry (3D forms)

CONVEX UPWARD DOUBLY CONVEXCONVEX DOWNWARDUNIFORM WEDGE

BENTUK FACIES (2-D)

UNIT FASIES (3-D )

WEDGING

SHEET

MOUND LENS


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Terminasi Refleksi

(Te) Truncationadalah terminai lateral suatu lapisan akibat terpotong dari

batas pengendapan aslinya.

(O) Onlapadalah baselap dimana lapisan yang awalnya horisontal laps-out

pada permukaan yang mulanya miring atau lapisan yang awalnya miring

laps-out updip pada lapisan yang lebih miring.

(D) Downlap adalah baselap dimana lapisan yang awalnya miring

terminates downdip pada bidang yang awalnya horisontal atau miring.

(T) Toplapadalah lapout pada batas atas sekuen pengendapan. Toplap

mencerminkan nondepositional hiatussedang erosional trunction

mencerminkan bidang erosi. (C) Concordancedapat terlihat pada batas atas dan bawah sekuen. Pada

bagian atas hubungan yang konkordandapat dikenali dari kesejajaran

lapisan dengan lapisan di bawahnya yang pada awalnya horisontal, miring

atai tidak teratur.


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Jenis dan notasi ABC untuk konfigurasi internal

sekuen seismik adalah :

Paralel (P), subparalel (Sp), divergent (D),

chaotic (c), reflection-free(Rf), mounded (M),

sigmoid (S), oblique (Ob), comples sigmoid-

oblique (SO),shingled (Sh),, hummockyclinoforms (HC), Even (E), Wavy (W),

Regular (R), Irregular (IR), Uniform (U),

Variable (V), Draped (Dr), Lenticular (L),Disrupted (D), Contorted (Co).


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Sekuen stratigrafi adalah studi stratigrafi yang berhubungan dengan

kerangka waktu pengendapan dalam kaitannya perubahan siklusmuka laut (global/regional) .

Setiap sekuen pengendapan terdiri dari perulangan perlapisan yang

dibatasi oleh permukaan erosi (UC) atau hiatus atau permukaan

yang selaras (C) (Van Wagoner et.al., 1987).

Sekuen dibatasi secara regional oleh ketidakselarasan (UC) atau

permukaan keselarasan (C) (Mitchum et.al., 1977).

Elemen penting dalam menentukan pola-pola sekuen stratigrafiadalah shelf/slope break.

Model Sekuen Stratigrafi


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Sequence Stratigraphy Diagram

BFF (Basin Floor Fan)

SFC (Slope Fan Complex)

PGC/LSW (Prograding Complex/ Lowstand Wedge)

TST (Transgressive Systems Tract)

MFS (Maximum Flooding Surface)

SB.1

(Sequence Boundary 1)

SB.2

(Sequence Boundary 2)

HST (Highstand Systems Tract)

SMST (Shelf Margin Systems Sract)

Vail et al, 1987

seismik stratigrafi migas

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