labuan field report: sedimentology

8/10/2019 Labuan Field Report: Sedimentology

1/23

SGGS 6113

RESERVOIR GEOLOGY AND SEQUENCE STRATIGRAPHY

LABUAN FIELD TRIP REPORT

By

ZAINAL AZIMUDIN BIN ZAINAL ABIDIN

SGI 140016


2/23

2

ABSTRACT

This report summarizes on the geological and stratigraphic distribution over Labuan Island.

The study was conducted by completing a litho-log of the sedimentary sequences describing

on the sedimentation of the rock. Generally there are 9 types of facies that is composed

together in various localities. 5 of the facies consist of sandstones with various sedimentary

features. 2 facies consist of shale and others are sub-facies that is not dominant like

conglomerate and coal. These lithofacies is then being interpreted into 5 different facies

association with interbedded relations. From the sedimentary sequences that have been

studied, a general implication towards petroleum system can be concluded.


3/23

3

CONTENTS

Page

Abstract 2

LIST OF FIGURES 4

1. INTRODUCTION 5

2. LITERATURE REVIEW 6

3. METHODOLOGY 9

4. RESULT

4.1 Facies Analysis 11

4.2 Facies Association 14

4.4 Implication of hydrocarbon and petroleum system 19

5. CONCLUSION 19

6. REFERENCES 20

7. APPENDIX 21


4/23

4

LIST OF FIGURES

Figure Description Page

1

Stratigraphic subdivision of Labuan Island based on previous study. Mazlan

(1994) disagree with all the previous authors on the existence of Setap

Shale Formation since both Brondijk (1962) and Wilson (1964) does not

describe the clear evidence of succession boundaries

6

2(A) Shows on the differences of horizontal measurement and true thickness

of the beds for dipping layer. (B) Shows the methods on using the Jacobs

Staff technique to measure dipping beds.

10

3 Figure 3. Map of Labuan showing the location of the outcrop locality. 10

A1Hummocky cross stratification at Kg. Ganggarak at the first 9 m of the log

just before the fault.21

A2 Thin shale with dominated sandstone at Kg. Ganggarak. 21

A3 Wave ripple cross lamination of sandstone shows the younging direction ofthe sequence.

22

A4 Coal clast sandstone of Tg. Kubong with size ranging from 2 cm to 5cm. 22

A5Shale dominated facies on the left part of the outcrop moving to the centre.

The thickness of the lithology of outcrop Kg. Bebuloh is 90m.23

A6Coal bed over Kg, Ganggarak shows a thin planar beddings which had

become friable due to weathering effect.23

A7 Field log 24


5/23

5

1. INTRODUCTION

Geology of Labuan Island is an important study of the geological and stratigraphic

distribution which is closely related to the geology of the offshore Sabah that is the Sabah

Basin and the East Baram Delta. This paper roughly explains on the stratigraphic geological

distribution of the facies and facies association for the entire outcrop of different locality in

Labuan Island.

The study covers on 6 different localities which cover an outcrop by the seashore and

hill cut nearby the main road as shown in figure 1. The localities that we have visited is Kg.

Ganggarak, Kiamsam Shell Terminal, Kg. Bebuloh, Tg. Layang-Layangan, Bkt. Kubong

Army Camp, Tg. Kubong and Bethune Head. Most of the outcrops have easy to moderate

accessibility since the vegetation that covers it is minimal. The rock beddings of the outcrop

are mostly tilted near to vertical exaggeration, making the succession easy to be recognized

and to be study.

The main objective of the study is to investigate and analyse the sedimentation process

that involve in creating the facies association and sedimentation structure. More detailed

objectives of the study are as follows:

1. To study on the stratigraphic succession of the outcrop of different localities in

Labuan Island.

2. To analyse the facies characteristic and facies associations within different localities.

3. To investigate on the process and environments involve in creating the stratigraphic

successions in Labuan Island.

4. To analyse potential petroleum system of Labuan Island based on the geological and

stratigraphic analysis.


6/23

6

2. BACKGROUND

Stratigraphic unit for Labuan Island is rather special since most of the

lithostatigraphic unit is being argued by one researcher to another. The main argument is the

presence of Setap Shale Formation in between the older Temburong Formation and younger

Belait Formation. The Setap Shale Formation was described by Liechti et al.s (1960) in their

compilation as the oldest unit as Temburong Formation. However, the theory is being

disproved by Brondijk (1962) and Wilson (1964) suggesting that Setap Shale is not a part of

Temburong Formation but another formation in between Belait and Temburong Formation.

Mazlan (1994) suggested that Setap Shale Formation is not there as a whole unit but

actually similar to Temburong Formation. Furthermore, he also added up the sequence

facies of Layang-Layang unit as a member of Temburong Formation. This paper will

generally discuss all the stratigraphic units despite which are correct resemblance of the true

lithostatigraphic of the area.

Figure 1. Stratigraphic subdivision of Labuan Island based on previous study. Mazlan (1994)

disagree with all the previous authors on the existence of Setap Shale Formation since both


7/23

7

Brondijk (1962) and Wilson (1964) does not describe the clear evidence of succession

boundaries. (Modified from Mazlan, 1994.)

Temburong Formation

Temburong Formation is the oldest formation of Labuan Island which covers roughly

the southern part of the island. It is the core structure of the Labuan anticline and considered

to be the same as the upper part of the West Crocker Formation is Sabah. Temburong

Formation based on outcrop observation by previous researcher mention that it consists

mainly of deformed deep water argillaceous deposits with rhythmic repetitions of siltstones

and shale interbedded together with claystone, limestone and special sandstone. Special

sandstone for the Temburong Formation would refer to its depositional characters.

Hutchison (2005) reported that Wilson (1964) has subdivided the Temburong

Formation of Labuan into a few sub-facies; (1) Nosong Formation: Consist of sandstone with

abundant lignitic films., (2) Kiam Sam Series: Consist of alternating layers of sandstone and

shale., (3) Limbayong Formation: Consist of claystone with some thick sandstone layers.

and, (4) Upper Sabong Formation: Consist of nodular claystone with thin sandstone and

some limestone layers. Addition to all the sub-facies described by Wilson (1964), Hutchison

(2005) add up what Mazlan (1994) have reported on the Layang-Layang Beds. Layang-

Layang Units as believed by Mazlan (1994) is a member of the Temburong Formation while

disagree as what Wilson (1964) suggested that Layang-Layang Units is as a part of Belait

Formation. Layang-Layang Units is mainly composed of siltstone and shale with thin

sandstone beds passing up into heterolithic sandstone with mudstone intercalations.

Depositional environment of the Layang-Layang Units has now changed to shallowing

upwards based on the thickening and coarsening-upwards trend and change from low-angle

parallel beddings to cross-stratification.


8/23

8

Setap Shale Formation.

Setap Shale Formation consists of succession of dark clay-shale generally with

intercalations of thin bedded sandstone or siltstone. Liechti et al.s (1960) reported that the

shale are occasionally calcareous and a few mostly thin lenses of biohermal or biostromal

limestone occur. The proportion of sandstones laminated together with the shale can be said

to be none since it is so small lamination, however, the both are still subordinate, component

of the formation. The researchers mention that the junction with the overlying Belait

Formation is generally conformable. Setap Shale Formation is deposited at the base of the

arenaceous feature-forming Belait Formation. Setap Shale Formation is believed to be below

the Belait Formation which has undergone compressional deformation and top erosion as

describe by both Brondijk (1962) and Wilson (1964) as in figure 1.

Belait Formation.

Belait Formation is the youngest unit for Labuan Island stratigraphic units which is

Middle to Upper Miocene. It composed with a few type of rocks, which is conglomerate and

pebbly sandstone at the base, passing upwards into alternating sandstone, shale and coal

(Mazlan, 1997). The deposition of the conglomerate forms the prominent and persistent

topographic ridges, marking the unconformable boundaries of underlying Temburong

Formation or Setap Shale Formation.?. Majority of the basal Belait Formation is medium to

very coarse grained fluvial pebbly sandstone and conglomerate while pebble-free medium to

fine grained sandstone and minor mudstone are deposited interbedded with the

conglomerate. It was reported that the erosive-based sandstone contain large coalified

driftwood and well-rounded coal fragments. The depositional succession continues upwards

into shallow marine deposits forming a heterolithic muddy facies. The sandstone facies is of

sharp-based sand bodies ranging from 0.3 to 1.5 m thickness, interbedded with fissile shale

up to 11 m thickness (Mazlan, 1997). Belait Formation was believed to be deposited fluvially

over an eroded area of Temburong Formation.


9/23

9

3. METHODOLOGY

The research and data gathering was conducted mainly on describing and analysing

the stratigraphic facies of the outcrop of different localities within the island of Labuan. The

methods used in gathering the data can be separated into a few different stages. The

equipments required to collect the data via these various stages is a geological compass

with clinometer, hand lens and 1 meter wooden staff. The initial step of collecting the

stratigraphic data is the reconnaissance stage. Reconnaissance stage is the primary step to

investigate on where is the younging direction of the outcrop of different localities. Since the

rock beds of the outcrop are not in horizontal position; mostly tilted beds, of all the localities,

therefore, determining the younging direction is very important. Younging direction of the

outcrop can be determined by observing carefully on the sedimentary structures distributed

along the stratigraphic line. Among the famous sedimentary structure is the ripple marks,

load cast, scour marks and burrow tracks.

The second stage of collecting stratigraphic data is by conducting the bedding

orientation measurement. The most common measurement that is required to define the

beds orientation is the dipping angles, dipping directions and strike direction of the beds.

Measurements of the beds dip-strike angles and directions would be very important for the

next important stage of the data collections that is the Jacob Staff measuring technique.

Jacob staff measuring technique is a technique used to measure the thickness of

tilted rock beds. Measuring the thickness of beds on horizontal plane would not give the true

thickness of the beds as describe in the figure XX.A. In order to measure the true thickness

of the beds, individuals must have the dipping angle of the beds together with its exact

dipping direction. From this information, we can point the staff to the correct direction, tilting

the staff according to the dipping of the beds as shown in figure XX.B. Based on the scale on

the wooden staff, we can easily collect the true thickness data. All the thickness, lithology


10/23


11/23

11

4. RESULTS

4.1 Facies Analysis

This facies analysis will focus on the lithology distribution with specified characteristic which

will be described as lithofacies. This study is only limited to lithofacies not the biofacies and

palynofacies. Lithofacies described as different rock types with specified sediment structure

which correlate to specified process involve in making these types of facies. Generally, for all

localities, there are 9 types of facies that is composed together or separately. The facies that

has been selected and grouped were described in the tables below.

Code Facies Description

F1

Sandstone with

hummocky cross

stratification.

Fine to medium grain sized sandstone with hummocky

cross stratification (H) and/or with planar cross bedding

(C). Thickness of the beds varies from 15 cm to 1.5 m.

The sedimentary structure size varies according to bed

thickness. Most of the hummocky structure is difficult to

identify due to weathering surface of the rock.

F2 Shale (thin).

Thin layer of shale with horizontal planar lamination and

minor cross lamination. Usually interbedded with thin to

thick layer of sandstone. Thin of the shale refer to less

dominant feature of the facies.

F3

Sandstone with

horizontal planar

bedding.

Fine to medium grain sized sandstone with simple

horizontal bedding and lamination. Usually interbedded

with thin layer of shale. More friable than any other

sandstone.

F4 Ripple Sandstone.

Sandstone with wave ripples cross lamination. Fine to

medium coarse sandstone with thickness varies from 15

cm to 2 m.


12/23

12

F5

Sandstone with coal

or mud clast and

lamination.

Fine to medium coarsening sandstone with minor coal or

mud clast and/or lamination. Beddings are thick ranging

from 60 cm to 2 m. Coal or mud content is very minor

(less than 5%).

F6 Dominant shale.

Shale with thick beddings and higher percentage in

specified unit. Usually interbedded with minor sandstone

(less than 40%) or exist as a massive unit.

F7 Conglomerate.

Matric supported conglomerate with sub-angular to sub-

round pebbles with size ranging from 2 to 5 cm.

Thickness of the is around 1.2 m thick.

F8Structureless

sandstone.

Usually exist in massive condition (more than 1 meter

thick). Grain size of medium to coarse.

F9 Coal beds

Friable condition of coal due to weathering. Thickness

varies up to 1.8 m. Coal breaks into planar structure and

have the shaly component.

F1 : Hummocky cross stratification in sandstone can exist in various depositional

environment based on a high energy events such as storms. It creates a smile-like feature of

the cross bedding which cross cutting each other layer as shown in appendix 1. It is formed

at a depth of water below fair-weather wave base and above storm wave base. It can exist in

shoreface and offshore environment.

F2: Thin shale for facies two describe as the interbedded shale with sandstone while the

shale is minor deposits compared to sandstone as shown in appendix 2. The thickness of

the thin shale ranging from 0.5 to 2 cm.

F3: The most dominant facies throughout Labuan Island is the interbedded horizontal planar

bedding of sandstone and shale. This type of sandstone have a friable condition which can


13/23

13

be interpreted as a good porosity. The thickness of the beds varies from 0.1 to 4 meter thick.

However, the beds are not stack up together with other sandstone but interbedded with

shale.

F4: Wave ripple sandstone or can also be interpreted as current ripple. Different between

these two is the properties of the ripples. Wave ripple tend to have a symmetrical wavy beds

while current ripple may be asymmetry. These describe the direction of the wave either

unidirectional or bidirectional. Appendix 3 shows the wave ripple cross lamination of Tg.

Kubong.

F5: Sandstone with coal or mud clast or lamination can occur usually after the coal or mud

being eroded, transported and deposited within sandstone beds. In order to bring the coal or

clast down, it requires a high energy environment such as in tide-influenced or fluvial

channel. Appendix 4 shows the coal fragment that has been consolidated inside sandstone

of Tg. Layang-Layangan.

F6 : Dominant shale refer to deposition of interbedded sandstone and shale with dominant

shale portion. Shale favour a lower energy depositional environment creating a thicker shale

portion to sandstone. Example of depositional area with dominant shale deposition is like in

prodeltaic system and offshore to deep marine. Example of dominant shale composition is in

outcrop Kg. Bebuloh as shown in appendix 5.

F7 : Conglomerate rock in this study exist in minimal portion if compared to shale and

sandstone. However, conglomerate brings good information in describing what environment

that influences the deposition of the surround rock. Conglomerate rock usually being

deposited in high energy environments such as in fluvial dominated channel, where the

deposition tend to be fining upward leading to heavier pebbles to drop at the bottom within

sand. Conglomerate in Kg. Ganggarak and Tg. Kubong can be correlated together. ?


14/23

14

F8: The structureless sandstone logged in Kg. Ganggarak have the thickness of 12.5 meter

and appear as a massive sandstone. The sand grains are well cemented and does not

appear to have good porosity.

F9 : Coal appear dominantly at Kg. Ganggarak with coal beds thickness around 2 meter.

The coal are friable which means it does not take enough force to break it with your hand.

This friable condition may be due to weathering effect. The coal also tend to break into its

planar structure as shown in appendix 6.

4.2 Facies Asssociation

Code Facies Associations Description and Interpretation

FA1 Interbedded sandstone

and shale. (Sandy)

Thickness of beddings ranging from 0.2 to 2 m thick,

coarsening and thickening upward succession with

hummocky cross stratification sandstone. Shale beds

have unclear lamination due to low bioturbation. Usually

the association will have sand domination around 60 to

75%. (Lower Shoreface)

FA2 Interbedded shale and

sandstone. (Shale)

0.2 to 6 m thick association of shale or mudstone with

sandstone lamination. Shale content dominant at 60 to 80

%. May have minimal micro hummocky cross

stratification. (Offshore)

FA3 Sequence of sandstone

with horizontal planar

beddings and/or

lamination, planar cross

beds and hummocky

cross stratification.

0.6 to 4 m thick sequence of sandstone with parallel

lamination interbedded with cross bed with possible

hummocky structure. Dominated mainly by sand with very

minimal shale or mudstone. Shows relative coarsening

and thickening upward trend. Maybe described at upper

shoreface to foreshore.

FA4 Sandstone shale Fining and thinnving upward with beds thickness ranging


15/23

15

interbedded with

horizontal planar

followed by cross bed.

from 0.1 to 1.5 m. Fine to medium grained sandstone with

cross bed structure alternating with horizontal planar

lamination. Beds have irregular to regular spacing. Have

abundant coal debris. (Fluvial to Tide-influenced channel)

FA5 Thick shale and mud

domination.

Succession usually very thick roughly more than 3 m thick

with structureless shale or mudstone. Sand content

usually below 50%. Follow coarsening and thickening

upward trend. (Prodelta)

FAULT

Log 1: Kg. Ganggarak.


16/23

16

Log 2: Kg. Kubong Army Camp.


17/23

17

Log 3: Kg. Bebuloh.


18/23

18

103 meter void. Eroded plus covered

with vegetation.

Log 4: Tg. Kubong.


19/23

19

4.3 Implications for Hydrocarbon Reservoir and Petroleum Systems.

Hydrocarbon reservoir and petroleum system over Labuan Island can be interpreted

based on sedimentary sequence. Potential hydrocarbon reservoir was interpreted to be at

the Tg. Kubong 1 where in the facies log shows the sedimentary sequence of thick

sandstone beds up to 40 meters. The conditions of the sandstone also way better that the

massive structureless sandstone at Kg. Ganggarak with possible higher porosity and

permeability percentage.

The major petroleum system for the sedimentary sequence can be described

chronologically. The best source rock can be said to be located either in Kg. Ganggarak coal

beds or Kg. Bebuloh black coaly shale. These source rocks are situated within the older

group formation that is the Temburong formation. The migration path is very unclear.

However, there are several faults that may associate with the migration. The reservoir rock

of Tg. Kubong 1 is situated in younger sequence at the top with possible seal or stratigraphic

traps of thick shale over at the edge of Tg. Kubong 2.

5. CONCLUSION

Sedimentary sequences of Labuan Island consist of 9 types of facies that is composed

together in various localities. 5 of the facies consist of sandstones with various sedimentary

features. 2 facies consist of shale and others are sub-facies that are not dominant like

conglomerate and coal beds. These lithofacies is then being interpreted into 5 different

facies association with interbedded relations. Generally, we can conclude that Kg.

Ganggarak is deposited dominantly in fluvial dominated channel, Kg. Kubong in prodeltaic

environment, Kg. Bebuloh in offshore to deep marine environment and Tg. Kubong in upper

to lower shoreface environment.


20/23

20

REFERENCES

Brondijk, J.F., 1963. Sedimentation in Northwest Borneo. Proc. Brit. Borneo Geol. Conf.

1961, Ceol SUrD. Dept. Bull. 4,19-26.

Coe, A. L. et al., 2010. Geological Field Technique. Department of Earth and Environmental

Sciences, The Open University, Walton Hall, UK. 26-28.

Hutchison, C.S., 2005. Geology of North-West Borneo. Elsevier. 421 pp.

Liechti, P., Roe, F.W. and Haile, N.S., 1960. The Geology of Serawak, Brunei and the

western part of North Borneo. British Territories of Borneo, Geological Survey Department,

Bulletin (Two volumes), 3, 360p

Madon, M.B.H., 1994. The stratigraphy of northern Labuan, NW Sabah Basin, East

Malaysia. Geological Society of Malaysia Bulletin 36, 1930.

Madon, M.B.H.,1997. Sedimentological aspects of the Temburong and Belait Formations,

Labuan (offshore west Sabah, Malaysia). Geological Society of Malaysia Bulletin 41, 6184.

Madon, M.B.H., Khee Meng, L., Anuar, A., 1999. Sabah Basin. The Petroleum Geology and

Resources of Malaysia. Petroliam Nasional Berhad (PETRONAS), pp. 499542

.

WILSON, R.AM., 1964. The Geology and Mineral Resources of the Labuan and Padas

Valley Area, Sabah, Malaysia. Geol. SUrD. Borneo Region, Mnlaysia, Mem. 17, 150 p .


21/23

21

APPENDICES

Appendix 1. Hummocky cross stratification at Kg. Ganggarak at the first 9 m of the log just

before the fault.

Appendix 2. Thin shale with dominated sandstone at Kg. Ganggarak.


22/23

22

Appendix 3. Wave ripple cross lamination of sandstone shows the younging direction of the

sequence.

Appendix 4. Coal clast sandstone of Tg. Kubong with size ranging from 2 cm to 5cm.


23/23

23

Appendix 5. Shale dominated facies on the left part of the outcrop moving to the centre. The

thickness of the lithology of outcrop Kg. Bebuloh is 90m.

Appendix 6. Coal bed over Kg, Ganggarak shows a thin planar beddings which had become

friable due to weathering effect.

labuan field report: sedimentology

Documents