STS51C-143-0027 Mississippi River Delta and Coastal Louisiana, US! "anuar# 1$%5
&!S! '()T)
STS*1!-42-0051 Mississippi River Delta, Louisiana, US! )+toer 1$%5 &
20 i &!S! '()T)
Outline
P etroleum etroleum systems ystems Geologic principles and geologic time Rock and minerals, rock cycle, reservoir properties Hydrocarbon ydrocarbon origin, migration igration and accum accumulation ulation Sedimentary environments; stratigraphic traps P late late tectonics tectonics,, struct ructur ural al geology Structural traps Geophys eophysical methods ethods Importance to Schlumberger
Cross Se+tion ). ! 'etroleu S#ste oreland asin 9:aple6 Geographic Extent of Petroleum System Extent of Play Reservoir
R
Stratigraphic Extent of Petroleum System
!+tive Sour+e Ro+/
9ssential 9leents o. 'etroleu S#ste
)verurden Ro+/ Seal or CapRo+/ Reservoir Ro+/ Sour+e Ro+/ Underurden Ro+/
'etroleu Reservoir R6 7old-and-T8rust elt arros indi+ate relative .ault otion6
# r l i a l t n 7 n e i s i a d 1 e S
aseent Ro+/ Top )il indo Top as indo
(modified from Magoon and Dow, 199! 4
'etroleu S#ste ! 'etroleu S#ste re;uires tiel# +onver
T8ese =n+lude> Seal or +ap ro+/ Reservoir ro+/ Mi
Petroleum Geology
"Law of cross-cutting relationships# $n the figure a%o&e, the igneous di'e (! is younger than layers )*E %ut older than layer G, %ecause a geologic feature is younger than any other geologic feature that it cuts# +his is an important law for determining the relati&e ages of geologic features# " )ccording to the Law of Superposition,” layer $- is older than layer .,- and the roc's %eneath the unconformity are older from right to left# rom the “Principle of Original Horizonality,” we infer that layers )- through - ha&e %een deformed# "Sedimentary roc' are deposited in successi&e layers that record the history of their time, much li'e the pages in history %oo'# /owe&er, the roc' record is ne&er complete# Missing layers (gaps in time! result in unconformities# " )n unconformity is a surface of non*deposition or erosion that separates younger roc's from older roc's# +he slide shows an angular unconformity# ) nonconformity is an unconformity in which younger sedimentary roc's o&erlie older metamorphic or intrusi&e igneous roc's
+he following are %asic principles or laws are used to e&aluate the relati&e ages and the relations among roc' layers# Uniformitarianism - +he present is the 'ey to the past#- 0y studying modern geologic processes, we can interpret past geologic e&ents and roc'*forming processes# Original Horizonality * Sedimentary layers are deposited in a horiontal or nearly horiontal position#- $f sedimentary layers are tilted or folded, they ha&e %een su%2ected to deforming stresses# Superposition * 3ounger sedimentary %eds occur on top of older %eds, unless they ha&e %een o&erturned or faulted#Cross-Cutting elations * )ny geologic feature that cuts another geologic feature is younger than the feature that it cuts#-
CrossCutting Relationships 6 . $ / G )ngular 4nconformity
5
E D l i l S s o u e $ g n
$gneous Di'e
0 )
Geologic Time Chart 9on 0
o < a1 s r a e #2 . o s n3 o i l l i 14 4*
9ra 'eriod 0
'8anero?oi+
6 + n a i i o r ? , o t p a + # r e C r ' 5
@uaternar#
Tertiar# o 50 < a c s 100 i o Creta+eous r 1 a e150 o s e "urassi+ # . M o200 Triassi+ s n250 'erian o i l l 'enns#lvanian i 300 M Mississippian 350 400 450
9po+8 0
Re+ent 'leisto+ene
o <10 'lio+ene a s r20 Mio+ene a e #30 )li
# r a d n o r i e t r a e u p a @ r E c # i d o r o a i 1 i r t o r e e p n T e
5
c i o Devonian 1 o Silurian e l a P )rdovi+ian
500 550
Carian
*00 7
eolo
:;< m#y
:= m#y
18 m#y
:9; m#y
: m#y 8 m#y
&onian period 40$ #
rian period
43$ # *5 #
1 %#y
57 # 510 #
570 #
E&olution of cells with nucleus
35 #
23 #
: %#y
5 #
%#y ;#;1 million years ago
#8 %illion years ago
E>) PE>$7D EP75/ /olocene epoch
7ldest fossil cells
%#y
7ldest roc's dated on Earth
!asic Geologic Principles Uniformitarianism - "#he present is the key to the past$% Original Horizonality "Sedimentary layers are deposited in a hori&ontal or nearly hori&ontal position$% Superposition "'ounger sedimentary beds occur on top o( older beds, unless they have been overturned or (aulted$% Cross-Cutting Relations ")ny geologic (eature that cuts another geologic (eature is younger than the (eature that it cuts$%
5
Classi(ication o( Rocks $G?E74S
. l o a e i r Molten aterials in + e deep +rust and r t u a upper antle o S < n i s Cr#stalli?ation r s e o + Solidi.i+ation o. elt6 . - o / r + p o R
SED$ME?+)>3
ME+)M7>P/$5
eat8erin< and erosion o. ro+/s e:posed at sur.a+e
Ro+/s under 8i<8 teperatures and pressures in deep +rust
Sedientation, urial and lit8i.i+ation
Re+r#stalli?ation due to 8eat, pressure, or +8ei+all# a+tive .luids
10
+he >oc' 5ycle Magma
5 o
o l i S n ( 5 o l i d g a i r y s f c a n d t a i t o l i 1 i
g
n i t l
e
M
a t i o
n
n !
Metamorphic >oc' !
d n
)
m
e s r i u h
s p
s r e o a r
t
e P m a
/
t
/eat and Pressure
@ e a t h e r i n a n g , + d D r an e p o p o s r s i t io n ta t io n ,
e
M (
Sedimentary >oc'
@eathering, +ransportation and Deposition 5 e m
e nt at on a n d i 5 o mpa c tio n
( Ai th if ica t i o n !
$gneous >oc' )
n d
D
e p o
s
+ r
a n
@
s e
p a
o h r e t a r t
i i t n t i i o o g n n ,
Sediment
Igneous Rocks Coprise $5A o. t8e 9art8Bs +rust )ri
"ol+ani+ -
12
Igneous Rocks and Reservoirs Igneous rocks can be part o( reservoirs$ *ractured granites (orm reservoirs in some parts o( the +orld$ olcanic tu((s are mi-ed +ith sand in some reservoirs$
Example: Granite Wash - Elk City, kla!, "#rthern $l%erta,C$
13
Sedimentary Rock #ypes " Relative aundan+e
Sandstone and +on
Siltstone, ud and s8ale 75A
17
.epositional /nvironments #he depositional environment can be0 Shallo+ or deep +ater$ 1arine 2sea3 and lake or continental$ #his environment determines many o( the reservoir characteristics
&ri'' Gas &iel( - "#rth )ea 18
.epositional /nvironments
Continental deposits are usually dunes$ ) shallo+ marine environment has a lot o( turbulence hence varied grain si&es$ It can also have carbonate and evaporite (ormation$ ) deep marine environment produces (ine sediments$
1*
Clastic Reservoirs
Consolidated and unconsolidate sands
Porosity 4
Permeability 4
.etermined mainly by the packing and mi-ing o( grains$
.etermined mainly by grain si&e and packing, connectivity and shale content$
*ractures may be present$
21
Clasti+ Sedientar# Ro+/s 5onglomerate
0reccia
Example
Sandstone
Shale
"Some sedimentary roc' types "re++ia * 5oarse*grained, angular fragments * little transportB "Con
Clastic Rocks Clastic rocks are sands, silts and shales$ #he di((erence is in the si&e o( the grains$
)i+e 24
)verage .etrital 1ineral Composition o( Shale and Sandstone Mineral Coposition
S8ale A6
Sandstone A6
Cla# Minerals
*0
5
@uart?
30
*5
4
10-15
E5
15
3
E1
E3
E1
7eldspar Ro+/ 7ra<ents Caronate )r
(modified from 0latt, 19<:! 23
Sedimentation
25
Clastic Sedimentary /nvironments 9nvironent
!
Sedients
Alluvial
Rivers
Sand,
La/e
La/e +urrents, aves
Sand, ud
Desert
ind
Sand, dust
la+ial
=+e
Sand,
Delta
River F aves, tides
Sand, ud
Beach
aves, tides
Sand,
Shallow shelf
aves, tides
Sand, ud
Deep sea
)+ean +urrents, settlin<
Sand, Mud
r'ani .aterial / 27
.epositional /nvironment .elta
Sediments are transported to the basins by rivers$ ) common depositional environment is the delta +here the river empties into the sea$ A good example of this is the Mississippi (Miocene and Oligocene sands)
28
Rivers
Some types o( deposition occur in rivers and sand bars$ #he river (orms a channel +here sands are deposited in layers$ Rivers carry sediment do+n (rom the mountains +hich is then deposited in the river bed and on the (lood plains at either side$ Changes in the environment can cause these sands to be overlain +ith a shale, trapping the reservoir rock$ 2*
Sandstone Composition *rame+ork Grains .atrix &rame#rk
@t? @uart?
@t? @uart?
#res @t? @t? @t? @uart?
!n/erite
Cement 31
Porosity in Sandstone 'ore T8roat
'ores 'rovide t8e olue to Contain (#dro+aron 7luids 'ore T8roats Restri+t 7luid 7lo
S+annin< 9le+tron Mi+ro
32
Clay .inerals in )an(st#ne eser#irs &i%r#s $thi'eni llite Se+ondar# 9le+tron Mi+ro
=llite
&e
"urassi+ &orp8let Sandstone (atters 'ond ield, !laaa, US!
'8oto
Clay .inerals in )an(st#ne eser#irs $thi'eni Chl#rite Se+ondar# 9le+tron Mi+ro
34
Clay .inerals in )an(st#ne eser#irs $thi'eni a#linite Se+ondar# 9le+tron Mi+ro
Si
Mi
Carter Sandstone &ort8 lo8orn Cree/ )il Unit la+/ arrior asin, !laaa, US!
'8oto
/((ects o( Clays on Reservoir 5uality !ut8i
!ut8i
1000
6 d -10 5 # t i l i , 1 a e r 01 e '
100 10 1 01 001
001 2
*
10
14
2
*
10
14
1%
'orosit# A6 odi.ied .ro Gu
Carbonate Reservoirs
Carbonates 2limestone and dolomite3 normally have a very irregular structure$ Porosity0 4
Permeability0 4
.etermined by the type o( shells, etc$ and by depositional and postdepositional events 2(racturing, leaching, etc$3$
.etermined by deposition and postdeposition events, (ractures$
*ractures can be very important in carbonate reservoirs$
37
Carbonate types
Chalk is a special (orm o( limestone 2CaCO63 and is (ormed (rom the skeletons o( small creatures 2cocoliths3$ .olomite 2Ca1g2CO6373 is (ormed by the replacement o( some o( the calcium by a lesser volume o( magnesium in limestone$ 1agnesium is smaller than calcium, hence the matri- becomes smaller and more porosity is created$ 4
888
/vaporites such as Salt 29aCl3 and )nhydrite 2CaSO:3 can also (orm in these environments$ 4
88 38
.epositional /nvironment Carbonates
Carbonates are (ormed in shallo+ seas containing (eatures such as0 4 Ree(s$ agoons$ 4 4 Shorebars$
3*
.iagenesis
#he environment can also involve subse
Chemical changes$ .iagenesis is the chemical alteration o( a rock a(ter burial$ )n e-ample is the replacement o( some o( the calcium atoms in limestone by magnesium to (orm dolomite$
4
1echanical changes (racturing in a tectonicallyactive region$
4
40
Source Rocks
Hydrocarbon originates (rom minute organisms in seas and lakes$ =hen they die, they sink to the bottom +here they (orm organicrich >muds> in (ine sediments$ #hese >muds> are in a reducing environment or >kitchen>, +hich strips o-ygen (rom the sediments leaving hydrogen and carbon$ #he sediments are compacted to (orm organicrich rocks +ith very lo+ permeability$ #he hydrocarbon can migrate very slo+ly to nearby porous rocks, displacing the original (ormation +ater$
42
/ydrocar%on Migration
Hydrocarbon migration takes place in t+o stages0 Primary migration (rom the source rock to a porous rock$ #his is a comple- process and not (ully understood$ It is probably limited to a (e+ hundred metres$ Secondary migration along the porous rock to the trap$ #his occurs by buoyancy, capillary pressure and hydrodynamics through a continuous +ater(illed pore system$ It can take place over large distances$
43
Structural Hydrocarbon Traps Shale
Oil
Gas Trap
) e a l
Closure
Oil/Gas Contact Oil/Water Contact Oil
Fracture Basement
Salt Dome
Fold Trap
Salt Diapir
il
(modiied rom B!orly""e# $%&%'
)r
itrinite
Disseinated )r
itrinite ! non.luores+ent t#pe o. or
Re.le+ted-Li<8t Mi+ro
44
Interpretation o( #otal Organic Carbon 2#OC3 2based on early oil +indo+ maturity3 (#dro+aron eneration 'otential
T)C in S8ale t A6
T)C in Caronates t A6
Poor
;#; * ;#=
;#; * ;#:
air
;#= * 1#;
;#: * ;#=
Good
1#; * :#;
;#= * 1#;
ery Good
:#; * =#;
1#; * :#;
=#;
:#;
Excellent
45
asi+ 9leents o. 'late Te+toni+s D$E>GE?+ 074?D)>3F Seafloor spreading Mid*ocean ridge
57?E>GE?+ 074?D)>3F Plate su%duction
Mountain %uilding
Aithosphere
.a'ma risin'
$sthen#sphere .a'ma 7#rmin'
"
Distri%ution of earthCua'es
5ontinental crust
olcanism
7ceanic crust
Sedimentary Basin and Stress Fields asin eoetries
7ault T#pes
-it -elated Basin (.tensional Stress' +ormal ault
Sedientar# 7ill
Foreland Basin (Compressi,e Stress' Thrust ault
ull)apart Basin (*ateral Stress'
Wrench ault 48
*olded Structures C#nex par(
11 0ge
0nticline
Syncline
50
" De.initions ) fold is a %end in the strata# )n anticline is a fold that is con&ex upward# +he oldest %eds occur in the center of an anticline# ) syncline is a fold that is conca&e upward# +he youngest %eds occur in the center of a syncline# ) monocline (not shown! is composed of strata that dip in one direction and are not 'nown to form a flan' of an anticline#
*old #erminology N
, i L
L i - ,
, i L
)nticline Syncline .#(iie( r#m xxx
3oungest roc' 7ldest roc'
51
aultin<
Stri"e Slip Fault (*et *ateral'
+
e " i r t S
Dip !n
Fault Plane 54
*aults +ormal Fault
-e,erse Fault Stri"e direction
Stri"e direction
4 p t F h a r u o l 3 t S n c a r p
Fault scarp D o 3 n t h r o 3 n
D o 3 n t h r o 3 n
F2W2
5ey bed
F2W2
H2W2
4 p t h r o 3 n
Dip angle
H2W2
Dip angle Fault plane
&ratre: 9#int an( &alt
Fault plane
52
Geologic >eser&oir /eterogeneity
56
Scales of Geological >eser&oir /eterogeneity $nterwell )rea
@ell
@ell
e Determined d i rom @ell Aogs, @ Seismic Aines, Statistical d l e Modeling, i ( etc#
1;;Hs m
1*1; 'm
l l e w r e t n $
>eser&oir Sandstone
1;Hs m
1;;Hs m
e r o 0 * l l e @
1;*1;;Hs m
Petrographic or Scanning Electron Microscope
1*1;Hs m
1;*1;;Hs mm
/and Aens or 0inocular Microscope
4naided Eye
(modified from @e%er, 19<8! 57
Hydrocarbon #raps
Structural traps
Stratigraphic traps
Combination traps
58
#raps General
Ghaar iliel( - )a(i $ra%ia- s - 145 mi x 13 mi i(e x260 t pr#(es 11,000 %;( t#tal 82< %%ls Gasharan iliel( - ran - s - 6000t! "et pay t#tal 8!5 < %%ls
5*
Structural Hydrocarbon Traps Shale
Oil
Trap
) e a l
Oil/Gas Contact
Gas
Closure
Oil/Water Contact Oil
Fracture Basement
Salt Dome
Fold Trap
Salt Diapir
il
(modiied rom B!orly""e# $%&%' 60
*ault #raps
*aults occur +hen the rock shears due to stresses$ Reservoirs o(ten (orm in these (ault &ones$ ) porous and permeable layer may trap (luids due to its location alongside an impermeable (ault or its ?u-taposition alongside an impermeable bed$ *aults are (ound in con?unction +ith other structures such as #r eerse &alt anticlines, domes "#rmal and salt domes$
Bra' &alts - Wy#min', m#st #ky .#ntains +ormal Faults - "i'eria, =i%enia >E! Cana(a, ?iks%r' @ren(s >?it#ria, @A
61
Stratigraphic #raps .ihi'an - e( D e(ater .i(lan(
#int
Petroleum /-ploration Geophysical 1ethods
Gravity methods
1agnetic surveys
Seismic surveys
64
Principle o( Gravity Surveys Un+orre+ted ravit# F1 ravit# -1 alue
Corre+ted ravit# ou
Clasti+s 24 <H+3
Salt 21 <H+3
65
Principle o( 1agnetic Surveys
Sedientar# asin aseent
F
Ma
>r#m xxx, 1*xx
66
Seismic Surveys #he seismic tools commonly used in the oil and gas industry are 7. and 6. seismic data Seismic data are used to0
@ .e(ine and map structural (olds and (aults @ Identi(y stratigraphic variations and map sedimentary (acies @ In(er the presence o( hydrocarbons
67
're-Drillin< Gnoled
Structural in(ormation obtained (rom sur(ace seismic data$ Rough geological in(ormation can be provided by nearby +ells or outcrops$ )ppro-imate depths estimated (rom sur(ace seismic data$
68
1arine )c
Cale it8 8#drop8ones
Re.le+ted aves
Sea ed
Sedientar# La#ers
6*
Crossline :AB 2/ast3 +
S Seal (unconormity' -eser,oirs
Source
70
)pplications o( Seismic .ata
1ake a structural model o( the reservoir .elineate and map reservoir
71
Stru+tural Map, L9 1$* 7ield B B F 7 D
* 1
*
; ; ; 9 1
:
8
;
;
; ; < : 1 *
D 7F B B
Stru+tural interpretation ased on 3-D seisi+ and ell lo< data
; ; : 1 *
) 2
;
; ; : : 1
; : 1 *
*
D 7 F B
; ; : * 1
B
; ; 8 1 1 *
D 7 : B B
B B : D
B B
D
Top Misoa C-4 Sand 9levation .t6 &
E D 7
D
7 B B B
B B 7 E
D
B B F
Sea*le&el datum
D D
11,400 -11,*00
B B
D D F B B
E D D
-11,*00 -12,000
D A E
-12,000 -12,400 -12,400 -12,%00
B
B :
7
N
D
;
) 2
; ( a
0
B B
u l t
-12,%00 -13,200 0
F
7 D
6 D
3000 .t 1000
B B
: 7 D
B
B
B
B : B 7 D
) 2 B B F
7 D
72
5hannels
Seismic 0mplitude 6ap o a Hori7on 3-B )eismi (ata (eine reser#irEality,hannel-ill san( (ep#sits
*luid evel !oundaries on 6. .ata ?ot $nterpreted
lat spot on seismic line indicates petroleum I water contact
$nterpreted
ault Modified from 0rown, 1998
74
/-ercise D D$ Oil (orms at lo+er temperatures than gas$ # * 7$ #he la+ o( 2original hori&ontality, uni(ormitarianism, superpos ition3 states that, in a normal sedimentary se
C$
Clastic rocks are (ormed (rom the materials o( older rocks the by actions o( erosion, transportation and $ Clastic rocks are sedimentary$ # *
E$
9ame t+o non clastic sedimentary rocks$ )$ !$
I$
)lluvial, desert, delta, beach and shallo+ shel( sediment make he best t reservoirs
DB$
# *
/-ercise 7 D$
D$ .iagenesis is the chemical alteration o( a rock a(ter burial$ # *
7$
21agnesium, Iron, or Sul(ate3 must be in the (ormation +ater in order to convert limestone to dolomite$
6$
;imestone is 2CaCO6 or Ca2CO6373$
:$
.olomite is 1gCaCO6 or 1gCa2CO637$
$
Ree( deposits are classi(ied as 2clastic, carbonate3 sedimentary rocks$
F$ A$ E$
#he source rock must contain 2organic material, coal, methane3$ *ault and anticline traps occur only in gas +ells$ # * #he oil +ater contact can be observed using seismic # *
$
2Historical, structural, tectonic3 geology addresses the occurrence and origin o( smaller scale de(ormational (eatures, such as (olds and (aults, that may be involved in hydrocarbon migration or +hich may (orm structural hydrocarbon traps$
DB$
Good
81
/-ercise 6 N 4
Well 4
3
3
4
2 1
a
% Well
( 82
" 5ircle the correct answer or la%el the drawing as directed# " 1# igure a- is a (normal, stri'e*slip, lateral! fault# " :# $f a well is drilled as shown on %loc' a- the target sandstone will most li'ely %e missing# + JJJ JJJ " # igure %- is a(n! (lateral fold, anticline, syncline!# " # $n igure %,- layer 1 K salt, : K sandstone, K shale, and Klimestone# 7n the figure, indicate the layer that is most li'ely ha&e trapped hydrocar%on# " =# igure c- is a(n! (right, left! lateral fault# " 8# 7n igure d,- the structure is a (normal fault, re&erse, stri'e*slip! fault# " L# ) well drilled at the location shown on igure d- will find strata (repeated, missing!#
/-ercise : D$
7$
6$ 6$
:$
$
Hydrocarbons reservoirs are normally in 2igneous, metamorphic, sedimentary3 rocks$ *luorescence o( drill cuttings or core indicates 2oil, gas, +ater3 is present$ Reservoir traps are 2very impermeable, highly permeable3$ =hat are 7 uses o( seismic data in petroleum e-ploration and development8 D$
7$
In inclined reservoir rocks, +hat is the signi(icance o( a "(lat spot% in seismic sections8 =hat is a :. seismic evaluation8
83
!asic Geologic Principles Uniformitarianism - "#he present is the key to the past$% Original Horizonality "Sedimentary layers are deposited in a hori&ontal or nearly hori&ontal position$% Superposition "'ounger sedimentary beds occur on top o( older beds, unless they have been overturned or (aulted$% Cross-Cutting Relations ")ny geologic (eature that cuts another geologic (eature is younger than the (eature that it cuts$%
5
"+he following are %asic principles or laws are used to e&aluate the relati&e ages and the relations among roc' layers# "Uniformitarianism - +he present is the 'ey to the past#- 0y studying modern geologic processes, we can interpret past geologic e&ents and roc'*forming processes# "Original Horizonality * Sedimentary layers are deposited in a horiontal or nearly horiontal position#- $f sedimentary layers are tilted or folded, they ha&e %een su%2ected to deforming stresses# "Superposition * 3ounger sedimentary %eds occur on top of older %eds, unless they ha&e %een o&erturned or faulted#"Cross-Cutting elations * )ny geologic feature that cuts another geologic feature is younger than the feature that it cuts#-
6A)S$$6)S$ 0)+4)? 0atuan merupa'an agregat padat yang terdiri dari mineral atau mineraloid, 'e%anya'an %atuan terdiri atas %e%erapa 2enis mineral (mineral, gelas, u%ahan mineral organi', dan 'om%inasi dari 'omponen*'omponen terse%ut! (Ernest G# Ehlers /ar&ey 0latt, 19<;!# 0atuan didefinisi'an 2uga se%agai 'umpulan mineral alamiah yang ter'ristal'an oleh Nproses pem%entu'an %atuanO (/uc'enhol, 19<:!#
"
9RD!S!RG!& 9&9S! D!& G)M')S=S=
0atuan 0e'u
0atuan Piro'lasti'
0atuan Sedimen
0atuan Metamorf
Distri%usi %atuan di %umi F " 0atuan %e'u di 'era' %umi %agian atas " 0atuan sedimen di permu'aan " 0atuan metamorf di inti dalam, mantel, 'era' %umi %agian %awah
!TU!& 9GU "
0atuan %e'u adalah %atuan yang ter%entu' a'i%at mem%e'unya magma pada wa'tu per2alannya menu2u 'e permu'aan %umi#
"
/asil dari pem%e'uan magma terse%ut mem%entu' %er%agai 2enis mineral yang mengi'uti aturan ting'at diferensiasi dari magma#
"
Magma adalah cairan sili'at yang panas dan pi2ar yang terdiri atas unsur*unsur 7, Si, )l, e, Mg, 5a, ?a, 6 dan se%againya#
" 6omposisi %atuan %e'u dapat di%eda'an dari 'omposisi secara mineralogi#F Mineral utama (oli&in, piro'sen, felspar, 'uarsa, plagio'las, ds%! Mineral tam%ahanF mineral yang ter%entu2 dari 'ristalisasi magma tapi 'ehadirannya sedi'it (contohF apatit, rutil, mineral %i2ih, ds%! Mineral se'underF mineral hasil u%ahan dari mineral*mineral primer (contohF 'lorit, epidot, dll!
6imiawi " 4nsur utama (ma2or element!F seperti unsur o'soda Si7:, )l:7, dll# " 4nsur 2e2a' (trace element!F seperti Sr, >%, 0a, dll# " 4nsur tanah 2arang (rare earth element!F seperti Aa, 5e, Pr, dll#
6lasifi'asi %atuan %e'uF Pada dasarnya 'lasifi'asi %atuan %e'u didasar'an pada te'stur dan mineralogi#
" a# 0erdasar'an te'sturF " $4GS ($nternational 4nion of Geological Sciences! mem%agi %atuan %e'u %erdasar'an pada %esar %utirF " 0atuan faneri' di'lasifi'asi'an se%agai %atuan plutoni', dimana %utirannya 'asar, sehingga secara indi&idu dapat di%eda'an, %er%utir 'asar*sedang ( 1 mm!# 6ristal*'rital yang le%ih %esar (feno'ris! tertanam dalam masa dasar yang le%ih halus (Gam%ar :!# 6lasifi'asi %atuan faneri' dila'u'an oleh $4GS, 19L (Gam%ar !# " 0atuan afaniti' di'lasifi'asi'an se%agai %atuan &ul'ani', dimana u'uran mineralnya terlalu 'ecil untu' di%eda'an, umumnya %er%utir haus ( 1mm!# 6lasifi'asi %atuan ini dapat dilihat pada Gam%ar #
" " " "
0erdasar'an mineralogi (Gam%ar =! Dasar 'lasifi'asiF 6omposisi (Q! mineral utama 6imiawiF "
" " "
sili'a (Q Si7:! F
ultra%asa (Si7: =Q!
%asa (Si7: = =:Q! intermediate (Si7: =: 88Q! asam (Si7: 88Q! "
alumina saturation
"
peralumina F 2enuh terhadap alumina ()l:7 ?a:7 R 6:7 R5a7! peral'aline F o'sida al'alin o'sida alumina su%alumina F o'sida alumina KI o'sida al'alin (?a:7 R 6:7! metalumina F o'sida alumina KI ?a:7 R 6:7 R5a7
color index
proporsi
mineral felsi' dan mafi'
"
0atuan Piro'lasti' adalah %atuan hasil letusan gunungapi# +erdiri atas material*material piro'lasti', yaitu pecahan gelasIa%uIde%u gunungapi, 'ristal, lithi'#
"
6lasifi'asi %atuan piro'lasti'F
"
Pada dasarnya pem%agian %atuan piro'lasti' didasar'an pada u'uran %utir# PenamaanF tuf, tuf lapili, %re'si piro'lasti' atau %re'si &ul'ani' (Gam%ar 8!# 4ntu' yang %er%utir halus ( mm!F tuff gelas, tuf 'ristal, tuf lithi' (+a%el 1!#
UKURAN CLAST (PECAHAN) > 64 mm
PIROKLAS
Bomb Block
+ , 64 mm
Lapll%! # Lapl
- + . /#/6 mm
B%$a" 0&b% ka!a B%$a" 0&b% 1al%!
- /#/6 mm
ENDAPAN PIROKLASTIK
NAMA BATUAN
Lap!a" bom#blok a$a% $&'a bom#blok Lap!a" lapl a$a% $&'a lapl D&b% ka!a
Alom&a$* b&k! pokla!$k
D&b% 1al%!
T%' 0&b% 1al%!
Lapll$o"& # $%' lapl T%' 0&b% ka!a
" Selain %atuan piro'lasti' ini 2uga di'enal %atuan epi'lasti', yaitu %atuan yang ter%entu' dari campuran atau rom%a'an material*material %atuan piro'lasti' (&ul'ani'! (Gam%ar L!# 5ontohF %atupasir &ul'ani', tuf pasiran, dll#
!TU!& S9D=M9& "
0atuan sedimen adalah %atuan yang %erasal dari rom%a'an %atuan yang telah ada yang telah mengalami si'lus sedimentasi (pelapu'an*transportasi* sedimentasi*diagenesa! (Gam%ar 9!#
" 6omposisi %atuan sedimenF ragmen mineralI%atuan hasil rom%a'an (terigen! Material hasil proses 'imiawi (material auttigeni'!, contohF 'ar%onat, fosfat# Material allochem (rom%a'an hasil presipitasi terdahulu!, contohF fosil, mineral organi', dll#
" 'en<
2 B&(0a!a(ka" a!al,%!%l"3a4 Kla!$k $&()&"o%! R%0$* a(&"$* l%$$
E"0apa" bokma . P&")&"0apa" bo)&"k . o()a"k kma Ba$%)amp")* I(o"!$o"&!* 0olom$* (6a")* &7apo($ 'o!'a$* ba$%ba(a
5olka"kla!$k T%'a* a)lom&(a$
atuan Sedien erdasar/an Te/stur "
0erdasar'an te'sturnya di%agi men2adi dua, yaitu yang %erte'stur 'lasti' (%erdasar'an me'anisme pengendapan!, dan %atuan yang %erte'stur non 'lasti' ('ristalin!#
"
"
atuan Sedien Glasti/
+erdiri atas material detritus (hasil rom%a'an I pecahan!, memperlihat'an te'stur 'lasti'# 4'uran %utir halus 'asar (Gam%ar 11!, di%agi %erdasar'an s'ala yang dinyata'an oleh @entworth (Gam%ar 1:!#
4nsur*unsur te'stur %atuan sedimen 'lasti'F " " " " "
" " "
"
0utiran (grain! F 'lasti' yang tertransport yang dise%ut se%agai fragmen# Matri's (masa dasar! F le%ih halus dari fragmenI%utiran, mengisi rongga antar fragmen, diendap'an %ersama*sama dengan fragmen# Semen F %eru'uran halus, mengi'at %utiranIfragmen dan matri's, diendap'an ditempat sedimentasi setelah fragmen dan matri's# Pemilahan (sorting! F dera2at 'esamaan atau 'eseragaman %utir# Dinyata'an dalam s'ala %ai', sedang, atau %uru'# Porositas F per%andingan &olume pori terhadap &olume %atuan secara 'eseluruhan# 0iasanya dinyata'an dalam Q atau dalam 'ualitas (%ai', sedang atau %uru'!# 0atuan dengan %utir yang seragam (terpilah %ai'! a'an mempunyai porositas yang relatif le%ih %esar dari %atuan dengan pemilahan %uru'# 5lay memili'i porositas yang paing %esar, lalu %atupasir dan 'emudian %re'si atau 'onglomerat# 6e%undaran F menyata'an 'e%undaran atau 'ta2aman %utiran yang mencermin'an ting'at a%rasi selama transportasi# Merupa'an sifat permu'aan dari %utiran yang dise%a%'an oleh pengaruh transportasi terhadap %utiran# 6emas (fa%ric! F merupa'an sifat hu%ungan antar %utir se%agai fungsi orientasi atau pac'ing# Dinyata'an dalam s'ala ter%u'a ('onta' antar %utiran tida' %ersentuhan! dan tertutup ('onta' antar %utiran saling %ersentuhan!# Permea%ilitas F 'emampuan %atuan melolos'an f luida, yang mencermin'an poriyang saling %erhu%ungan# 0atupasir merupa'an %atuan dengan permea%ilitas yang %ai', sedang'an clay walaupun memili'i porositas %ai' tapi permea%ilitasnya yang %uru'# 6arena mineral dalam clay termasu' 'edalam minera pirosili'a yang %ersifat 'ondu'tif, sehingga clay ini mengi'at 'ation yang a'an mengi'at 7/# 7leh 'arena itu clay memili'i sifat swelling (dapat mengem%ang %ila ter'ena air!, yang menye%a%'an resisti&ity dari clay ini sangat rendah (Gam%ar 1!# Stru'tur sedimen F penyimpangan dari %idang perlapisan# Stru'tur sedimen ini mencermin'an me'anisme yang mempengaruhi pengendapan %atuan sedimen# 5ontohF strutur sedimen pada me'anisme arus tur%idit yang dinyata'an oleh 0ouma dalam Si'uen 0ouma#
atuan Sedien &on-Glasti/ "
4mumnya tersusun atas mineral autigeni' (ter%entu' di tempat sedimentasi!# Pada P dan + tertentu sering'ali memperlihat'an ge2ala diagenesa, a'i%atnya porositas %atuan men2adi sangat rendah atau %a'han tida' ada# Porositas primer rendah dan memperlihat'an te'stur moai' (contoh %atugamping!# 6adang* 'adang terdapat %utiran yang amorf (seperti 'alsedon dan opal! se%agai semen#
atuan Sedien Giiai "
+er%entu' a'i%at perananIpengaruh proses*proses 'imia dari larutan# +erdiri atas %atuan 'ar%onat dan %atuan e&aporit#
atuan Garonat "
"
0atuan 'ar%onat adalah %atuan sedimen yang mempunyai 'omposisi garam*garam 'ar%onat yang dominan ( =;Q!# Proses pem%entu'annya dapat secara insitu, %erasal dari larutan yang mengalami proses 'imiawi maupun %io'imiawi# 6omposisi 'imia dan mineralogi %atuan 'ar%onatF )ragonit (5a57 orthorom%i'! 6alsit (5a57 hexagonal! Dolomit (5aMg(57!:! Magnesit (Mg 57!
Porositas %atuan 'ar%onatF " )da dua macam 'lasifi'asi porositas dalam %atuan 'ar%onatF " menurut Murray (198;! merupa'an 'lasifi'asi %erdasar'an pada genesa, di%agi men2adiF Porositas primer F ter%entu' pada saat sedimentasi %erlangsung# +erdiri atas porositas 'erang'a frame* wor' porosity!, porositas lumpur (mud porosity!, dan porositas pasir (sand porosity!# Porositas se'under F ter%entu' setelah pengendapan, a'i%at pelarutan, re'ahan atau peru%ahan yang ter2adi setelah proses sedimentasi# Sucrose dolomite porosity F ter%entu' se%agai a'i%at adanya penggantian 'alsit oleh dolomit#
"
menurut 5hoCuette anfd Pray (19L;! merupa'an 'lasifi'asi des'riptif dan geneti'# 4nsur*;unsurnya terdiri atasF
0asic porosity typesF "
" "
fa%ric selecti&e F interparti'el, intraparti'el, inter'ristalin, moldic, fenestral, shelter, growth framewor'# ?on fa%ric selecti&e F fracture, channel, &uggy, ca&ern a%ric selecti&e or not F %reccia, %oring, %urrow, shrin'age#
Modifying terms F genetic modifiers, sie modifiers, a%undance modifiers#
6lasifi'asi %atuan 'ar%onat " 6lasifi'asi dalam %atuan 'ar%onat antara lain di'emu'a'an oleh Gra%au (191!, ol' (19=!, Petti2ohn (19=L!, Dunham (198:!, Em%ry and 6lo&an (19L:!, dll# " 6lasifi'asi yang %anya' diguna'an dalam penggolongan %atuan 'ar%onat adalah 'lasifi'asi menurut Dunham, dan Em%ry and 6lo&an, 'arena 'lasifi'asi ini cu'up sederhana dan mudah dalam pemna'aiannya#
Klasifikasi Dunham (1962) " 6lasifi'asi ini didasar'an pada te'stur pengendapan (Gam%ar 1L!# a'tor yang penting dalam 'lasifi'asi ini adalahF " 0utiran didu'ung lumpur (mud supported! " 0utiran saling menyangga (grain supported! " Se%agian %utiran didu'ung lumpur, se%agian %utiran saling menyangga (parteil!
Klasifikasi m!ry and Klovan (19"2) " Merupa'an modifi'asi dari 'lasifi'asi Dunham, didasar'an pada terdapatnya lumpur diantara 'erang'a atau pecahan 'erang'a (Gam%ar 1!#
atuan 9vaporit "
Merupa'an %atuan garam yang ter%entu2 2arena e&aporasi air laut## Mineral penyusunnya %ersifat monominerali', antara lainF garam (5aS7 :/:7!, anhidrit (5aS7!, dan halit (?a5l!
!TU!& M9T!M)R "
0atuan metamorf adalah %atuan yang ter%entu' a'i%at proses peru%ahan te'anan (P! dan temperatur (+! atau 'eduanya, dimana %atuan memasu'i 'esetim%angan %aru tanpa adanya peru%ahan 'omposisi 'imia (iso'imia! dan tanpa melalui fasa cair (dalam 'eadaan padat! dengan temperatur %er'isar :;;*<;;T 5#
Peru%ahan yang ter2adi dalam proses metamorfosaF peru%ahan te'stur dan stru'tur (yang merefle'si'an se2arah pem%entu''annya!B dan asosiasi mineral# Stru/tur atuan etaor.> " Stru'tur foliasi (schistosity! stru'tur paralel yang ditim%ul'an oleh mineral pipihImineral prismati', sering'ali ter2adi pada metamorfosa regional dan metamorfosa 'ata'lasti'# " Stru'tur non foliasi stru'tur yang di%entu' oleh mineral*mineral yang eCuidimensional, sering'ali ter2adi pada metamorfosa termal#
eerapa stru/tur atuan etaor. F !ang "ersifat foliasi# " " " " " "
Slaty clea&age planar, di2umpai %idang %elah %atu sa%a'Islate# iliti' re'ristalisasi le%ih 'asar dari slaty clea&age# Shistose stru'tur perulangan dari mineral pipih dan mineral granular dimana mineral pipih orientasinya menerus (tida' terputus!# Gneisose stru'tur perulangan dari mineral pipih dan mineral granular dimana mineral pipih orientasinya terputus, sering dise%ut close schistosity# Miloniti' menun2u'an goresan*goresan a'i%at penggerusan yang 'uat# iloniti' ge2ala dan 'enampa'an sama dengan miloniti', hanya disini %utirannya le%ih halus#
!ang "ersifat non foliasi# " Granulose terdiri atas mineral granular " /ornfelsi' identi' dengan grano%lasti', tapi mineral eCuidimensional# Aepido%lasti' terdiri atas mineral pipihIta%ular " ?emato%lasti' terdiri atas mineral prismati' " Grano%lasti' terdiri atas mineral granular " /omeo%lasti' terdiri atas satu te'stur sa2a " /etero%lasti' terdiri atas %e%erapa te'stur " >elic (sisa! te'stur sisa yang ter%entu' se%elum metamorfosa " 6ristalo%lasti' setiap te'stur yang ter%entu' pada saat metamorfosa " )walan meta- %ila masih di'enali sifat %atuan asalnya, seperti metasedimen, meta&ol'ani', dll#
C)&T=&9&T!L S9D=M9&T!RI 9&=R)&M9&TS Copyright � 1998 Pamela J. W. Gore !LLU=!L 7!&
7LU=!L
L!CUSTR=&9
D9S9RT DU&9S6
'!LUD!L
Ro+/ T#pe
0reccia, conglomerate, ar'ose
5onglomerate, sandstone, siltstone, shale
Siltstone, shale, limestone, or e&aporites (gypsum!
Uuart arenite (sandstone! or gypsum
Peat, coal, %lac' shale, siltstone
Coposition
+errigenous
+errigenous
+errigenous, car%onate, or e&aporite
+errigenous or e&aporite
+errigenous
Color
0rown or red
0rown or red
0lac', %rown, gray, green
3ellow, red, tan, white
0lac', gray, or %rown
rain Si?e
5lay to gra&el
5lay to gra&el (ining upward!
5lay to silt or sand (5oarsening upward!
Sand
5lay to silt
rain S8ape
)ngular
>ounded to angular
***
>ounded
***
Sortin<
Poor
aria%le
aria%le
Good
aria%le
=nor
5ross*%edding and graded %edding
)symmetrical ripples, cross* %edding, graded %edding, tool mar's
Symmetrical ripples, lamination, cross*%edding, graded %edding, mudcrac's, raindrop prints
5ross*%edding
Aaminated to massi&e
)r
***
+rac's, trails,%urrows
+rac's, trails, %urrows, rare stromatolites
+rac's, trails
>oot mar's, %urrows
7ossils
***
>are freshwater shells, %ones, plant fragments
reshwater shells, fish, %ones, plant fragments
***
Plant fossils, rare freshwater shells, %ones, fish
M!R=&9 S9D=M9&T!RI 9&=R)&M9&TS Copyright � 1998 Pamela J. W. Gore R99
C)&T=&9&T!L S(9L
C)&T=&9&T!L SL)'9 !&D R=S9
!ISS!L 'L!=&
Ro+/ T#pe
ossiliferous limestone
Sandstone, shale, siltstone, fossiliferous limestone, oolitic limestone
Aitharenite, siltstone, and shale (or limestone!
Shale, chert, micrite, chal', diatomite
Coposition
5ar%onate
+errigenous or car%onate
+errigenous or car%onate
+errigenous or car%onate
Color
Gray to white
Gray to %rown
Gray, green, %rown
0lac', white red
rain Si?e
aria%le, framewor's, few to no grains
5lay to sand
5lay to sand
5lay
rain S8ape
***
***
***
***
Sortin<
***
Poor to good
Poor
Good
=nor
***
Aamination, cross* %edding
Graded %edding, cross*%edding, lamination, flute mar's, tool mar's (tur%idites!
Aamination
)r
***
+rails, %urrows
+rails, %urrows
+rails, %urrows
ossils
5orals, marine shells
Marine shells
Marine shells, rare plant fragments
Marine shells (mostly microscopic!
