LATERAL DISTRIBUTION OF SANDSTONE MATURITY IN … LATERAL...Surono, Toha, B, dan Sudarno, I., 1992,...

PROCEEDING, SEMINAR NASIONAL KEBUMIAN KE-8 Academia-Industry Linkage

15-16 OKTOBER 2015; GRHA SABHA PRAMANA

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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.



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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



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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



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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



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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).



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Figure 2. Stratigraphic column of southern mountain (Surono, et al., 1992)



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Figure 3. Grouping of sandstone maturity at lower channel submarine fan (Boggs, 2006).

Figure 4. Turbid current through slope of submarine (Shanmugam, 2006).



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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 (%)



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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 (%)



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Figure 9. Outcrop photo with black line as focus part of study.

LATERAL DISTRIBUTION OF SANDSTONE MATURITY IN … LATERAL...Surono, Toha, B, dan Sudarno, I., 1992,...

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