PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
523
LATERAL DISTRIBUTION OF SANDSTONE MATURITY IN LOWER PART OF
SUBMARINE FAN CHANNEL: A STUDY CASE FROM SEMILIR FORMATION,
BANTUL DISTRICT, SPECIAL REGENCY OF YOGYAKARTA, INDONESIA
Bima Eko Dhanu*, Dwi Tantra Mega Saputra, Rahmadi Hidayat Department of Geological Engineering, Faculty of Engineering, Universias Gadjah Mada
Address: Jalan Grafika 2, Bulaksumur, Yogyakarta 55281- Indonesia *corresponding author: [email protected]
ABSTRACT Submarine fan channel is one of highly prolific reservoir in Indonesia, such as deeper Kutai Basin in
Makassar Strait. Compare to common fluvial channel system, lateral distribution of maturity as well
as may due to turbidity system. In this maturity have more complex study, model of lateral distribution
of submarine fan channel, especially in lower part, is proposed to reveal the complexity of this system.
Data was collected from single channel sand body in Semilir Formation which is located in Piyungan
Subdistrict. The study was conducted in single layer which is affirmed has relation horizontally, then
we conducted analysis of mineralogy to get major minerals data, such as quartz, feldspar, matrix
abundant of thin sections petrographically and also grain size by handy observation. The result of this
study was expected to inform us that there are maturity trend related to major minerals (quartz,
feldspar, matrix). The study is important for petroleum industry to enhance target in searching good
maturity of sandstone reservoir body and also could be optimize hydrocarbon production in the field.
I. INTRODUCTION
More than 1.200 oil and gas field known from
the deepwater systems (Stow and Mayall,
2000). The successful of the deepwater
exploration are known generally in Gulf of
Mexico, while in Indonesia the potential deep
water petroleum system which recognized has
a great potential in North Makassar Strait is
considered that the sediments carried by
upstream in mainland of Kutai Basin.
Deepwater system in simplify showed by
submarine fan which deposited by turbidity
current (Shanmugam, 2006). One of geological
feature in deepwater system is channel,
certainly has different system than channel
system in terrestrial. Rock formation which
placed in Southern Mountain with deepwater
environment which has uniqueness and
interesting be studied to make analogue
modern submarine system, is Semilir
Formation.
Study area is located in astronomically at 49 M
0436978 E and 9130078 N in UTM unit and
administratively located in the Piyungan
village, Bantul, Special Regency of Yogyakarta
in southeast of Yogyakarta City, distance from
UGM campus is about 18 km and to reach
study location can be used by motor vehicle
and need around 40 minutes from UGM
campus.
Objective of this study is try to reveal
differences in sandstone maturity in outcrop
scale, showing variation of sediment flows in
the same channel, and finding existence of
heterogenity mineral composition of rock at
base submarine fan
II. GEOLOGICAL FRAMEWORK
As a part of rock formation is located in
Southern Mountain complex certainly Semilir
Formation structurally following dynamic
structure in the area. According to van
Bemmelen (1949) geological structure
patterns regionally are likely to follow Semilir
Formation i). N-S direction, which is largely
sinistral strike-slip fault from Middle Miocene,
ii). NW-SE direction, which is generally dextral
strike-slip fault on Late Pliocene, iii). E-W
direction, usually normal fault due to
stretching N-S that growing on Early
Pliestocene. And minor structure, found in the
outcrop such as joint structure.
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
524
Stratigraphic Framework
Semilir Formation conformably overlie Kebo-
Butak Formation, but locally found
unconformity structure (van Bemmelen, 1949).
This formation interfingering with Nglanggran
Formation and Sambipitu Formation but
unconformably suppressed by Oyo Formation
(Surono, et al., 1992). Semilir Formation is
composed of tuff sandstone, pumice breccias,
and intercalation sandstone and siltstone, this
formation is aged Early-Middle Miocene with
shallow sea (strong current) to deep water
depositional environment are affected by sea
(Surono, et al., 1992). Semilir Formation is also
rock formation which formed by gravity flow
deposits were interpreted passes through
slope of submarine and marked by structure
slump, is typically the sediment is transported
and and deposited on slope. In outcrop scale,
the study area showed good bedding plane
and well preserved, so that helping the
authors observing outcrop and retrieving the
necessary data.
III. SAMPLE AND METHODS
This study uses primary data such as outcrop
data and petrographic data. Outcrop of Semilir
Formation used to get know sedimentology
laterally by limiting the outcrop and assessing
it as tip-by-tip of the channel and just focus at
lower part of channel with width about 36
meter, while petrographic data used to
observe minerals of sandstone mainly quartz,
feldspar, matrix, and lithic or rock fragments.
Sample in outcrop were taken every 3 meter
regularly, which respectively starting from
west to east BM-01; BM-02; BM-03; BM-04;
BM-05; BM-06; BM-07; BM-08; BM-09; BM-10;
BM-11; and BM-12.
Furthermore, after outcrop observed
sedimentologically in the field, samples which
were taken observed under microscopic to
observe major constituent of rock mainly
quartz, plagioclase, matrix and lithic, then
calculated in each sample and made
composition trend of each sample so that can
be withdrawn its trend and showed variations
in rock composition became evidence of
heterogeneity sandstone at lower part of
submarine fan channel laterally.
IV. DATA DAN ANALYSIS
The study uses primary data from outcrop and
petrography data. Outcrop data has function
to give information sedimentology and
sediment process in megascopic and
petrography give information more detailed in
petrographically and data were got from
petrographic is calculated and made its trend
used MS-Excel.
V. RESULT AND DISCUSSION
Maturity Sandstone
Based on the composition of rocks observed in
petrographic can be concluded that the
sandstone in study area belongs to lithic
wacke and referred to Pettijohn’s
classification (1975). It is based on the content
of mud in the range 15-75 % and dominated
by lithic or rock fragment content.
The term maturity is applied to sandstones in
two different ways. Compositional maturity
refers to the relative abundance of stable and
unstable framework grains in a sandstone. A
sandstone composed mainly quartz is
considered compositionally mature, whrereas
a sandstone that contains abundant unstable
minerals, feldspar for instace or unstable rock
fragments is compositionally immature.
Textural maturity is determined by the
relative abundance of matrix and degree of
rounding and sorting of framework grains
(Boggs, 2006). In the study, sandstone belongs
to immature-submature texture, due to grain
are not well-sorted and well rounded by
observation under microscopy of petrography
data and observation sandstone in the field.
Sediment Flows
Most sediments are deposited in deep water
transporting across shelf to reach deeper
environment. Coarse-grained sediment
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
525
movement through shelf by turbid current,
while fine-grained sediment transported by
nepheloid flow and sediment plume (Boggs,
2006). Focus of grain size for this study area is
coarse sediment and it is clear that sedimen
controlled by turbid current as a single control
mechanism which carries sediment through
submarine channel (Nomark and Piper, 1991).
Locally in channel also have variations in
composition of minerals in rock is seen at
lower part of channel especially major
minerals such as quartz, feldspar, matrikx and
rock fragments.
Heterogenity of Base Channel
Heterogeneity at lower channel in detailed
scale showing that at same time deposition
has heterogeneity of mineral composition.
This variation showing that difference
transportation flow and deposition in the
context laterally. Thus, the variation is hoped
become a clue that deepwater exploration at
lower part of submarine channel as target
reservoir and recognized give impact on
exploitation and production of reservoir.
VI. CONCLUSION
In the submarine fan channel environment has
a relationship in single channel at same time
deposition showing heterogeneity
composition mineral of rock and also sandtone
maturity. These variations and heterogeneity
is recognized has difference transport and
sediment flow in single channel. And finally, it
may affect to reservoir intervention to
optimize exploitation and production and
need further research to know how far this
evidence help reservoir optimization.
VII. ACKNOWLEDGEMENT
The authors would like to thank Geological
Department, Faculty of Engineering,
Universitas Gadjah Mada and also to the
committee which give opportunity to publish
this paper at Seminar Nasional Kebumian
UGM tahun 2015 in Yogyakarta
REFERENCES Boggs, Sam, Jr., 2006. Principles of Sedimentary and Stratigraphy 4th Edition. New Jersey, Pearson Prentice-Hall.
Normark, W.R.., Piper, D.J.W., 1972, Sediment and growth pattern of Navy deep-sea fan, San Clemente Basin, California borderland, Journal of Geology, 80.
Rahardjo, W., Sukandarrumidi, dan Rosidi, H.M.D., 1977, Peta Geologi Lembar Yogyakarta, Jawa, skala 1:100.000. Pusat Penelitian dan Pengembangan Geologi, Bandung.
Shanmugam, G., 2006, Deep-water Processes And Facies Models: Implication for Sandstone Petroleum Reservoirs.
Stow, D.A.V., dan Mayall, M, 2000, Deep-water sedimentary systems: new models for the 21st century, Marine and Petroleum Geology, 17.
Surono, Toha, B, dan Sudarno, I., 1992, Peta Geologi Lembar Surakarta, Jawa, skala 1:100.000. Pusat Penelitian dan Pengembangan Geologi, Bandung.
TABLES Table-1 Mineral composition of sandstone
Point Scope of
view
Minerals Composition (%)
Quartz Feldspar Matrix Lithics Others
BM-01 1013637 5 10 40 30 15
1013641 5 15 40 35 5
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
526
1013644 5 20 35 30 10
1013647 5 10 40 30 15
Mean 5 13.75 38.75 31.25 11.25
BM-02 1013651 10 10 35 20 25
1013654 15 10 40 15 20
1013657 10 15 35 30 10
1013660 10 10 45 30 5
Mean 11.25 11.25 38.75 23.75 15
BM03 1013773 15 10 35 25 15
1013776 10 15 30 30 15
1013779 10 15 35 15 25
1013782 10 10 25 35 20
Mean 11.25 12.5 31.25 26.25 18.75
BM-04 1013737 5 5 45 30 15
1013740 5 10 40 35 10
1013743 5 15 40 25 15
1013746 5 5 35 40 15
Mean 5 8.75 40 32.5 13.75
BM-05 1013663 3 5 60 10 22
1013666 5 8 45 15 27
1013669 15 5 35 25 20
1013672 5 10 45 15 25
Mean 7 7 46.25 16.25 23.5
BM-06 1013687 5 10 40 15 30
1013690 5 15 40 20 20
1013695 10 15 55 10 10
1013698 5 10 35 30 20
Mean 6.25 12.5 42.5 18.75 20
BM-07 1013725 5 8 55 30 7
1013728 10 8 45 35 2
1013731 5 5 40 45 5
1013734 10 5 40 40 5
Mean 7.5 6.5 45 37.5 4.75
BM-08 1013761 12 10 45 25 8
1013764 15 5 30 45 5
1013767 20 5 30 35 10
1013770 15 4 45 30 6
Mean 15.5 6 37.5 33.75 7.25
BM-09 1013749 20 8 45 25 2
1013752 15 10 35 25 15
1013755 20 10 35 30 5
1013758 20 14 25 35 6
Mean 18.75 10.5 35 28.75 7
BM-10 1013701 8 4 60 20 8
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
527
1013704 5 10 45 35 5
1013707 8 5 60 25 2
1013710 5 4 65 20 6
Mean 6.5 5.75 57.5 25 5.25
BM-11 1013713 25 10 20 40 5
1013716 15 8 25 40 12
1013719 15 8 45 25 7
1013722 15 10 35 35 5
Mean 17.5 9 31.25 35 7.25
BM-12 1013675 25 10 30 30 5
1013678 40 8 20 25 7
1013681 25 5 30 30 10
1013684 25 5 50 15 5
Mean 28.75 7 32.5 25 6.75
FIGURES
Figure 1. The study area in geological map (Raharjo, et al., 1995).
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
528
Figure 2. Stratigraphic column of southern mountain (Surono, et al., 1992)
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
529
Figure 3. Grouping of sandstone maturity at lower channel submarine fan (Boggs, 2006).
Figure 4. Turbid current through slope of submarine (Shanmugam, 2006).
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
530
Figure 5. Quartz trend at lower channel from left is reflected as west of outcrop and right is reflected
as east of outcrop
Figure 6. Feldspar trend at lower channel from left is reflected as west of outcrop and right is
reflected as east of outcrop
0
5
10
15
20
25
30
35
0 5 10 15
Quartz
Quartz
Poly. (Quartz)
0
2
4
6
8
10
12
14
16
0 5 10 15
Feldspar
Feldspar
Poly. (Feldspar)
Sample location
Content (%)
Sample location
Sample location
Content (%)
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
531
Figure 6. Matrix trend at lower channel from left is reflected as west of outcrop and right is reflected
as east of outcrop.
Figure 7. Lithic or or rock fragment trend at lower channel from left is reflected as west of outcrop
and right is reflected as east of outcrop.
Figure 8. Outcrop section with sample point. Showing geological feature form likely channel with
southwestward to observer.
0
10
20
30
40
50
60
70
0 5 10 15
Matrix
Matrix
Poly. (Matrix)
0
5
10
15
20
25
30
35
40
0 5 10 15
Lithics
Lithics
Poly. (Lithics)
Sample location
Content (%)
PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage
15-16 OKTOBER 2015; GRHA SABHA PRAMANA
532
Figure 9. Outcrop photo with black line as focus part of study.