proceedings of international conference on geological

Proceedings of International Conference on Geological Engineering

Geological Engineering Department, Engineering Faculty, Gadjah Mada University

December, 11-12 2013

iii

Message from Head of Geological Engineering Department,

Gadjah Mada University

This proceeding consists of selected papers presented on the International

Conference on Geological Engineering (ICGE) held in Yogyakarta, Indonesia, December

11–12, 2013, which is hosted by Geological Engineering Department, Faculty of

Engineering, Universitas Gadjah Mada (GED-UGM). The ICGE 2013 conference is the

first year program on Geological and Georesources Engineering on phase III of

AUN/SEED-Net. As the host institution for ICGE 2013, GED-UGM becomes the center

for the continuation of international relationships in geological and georesources

engineering fields.

The ICGE 2013 that addresses strengthening geo-resources and geo-engineering

management for green economic growth accommodate for more than 12 various topics

related to geological and georesources engineering discussed in this conference. Those are

earth resources, exploration geosciences, environmental geosciences, hydrogeology, slope

stability, landslides susceptibility, rock mechanics, strategic development, mineral

resources, safety management, mineral processing techniques, industrial minerals, and

more topics that related to geological engineering. ICGE 2013 aims at creating dialogue

between academics, experts, governments, and industries as well as those who have

interest in addressing those issues in the international level. We expect solutions for the

problems arise from the participants during this event to be adopted to help resolve global

geological engineering problems.

Sponsorship of this meeting is an important feature of its success. On behalf of the

host institution Geological Engineering Department, Faculty of Engineering, Universitas

Gadjah Mada, we thank the sponsors who have helped to promote the meeting and

supported the events.

I wish this proceeding can give a big contribution for developing research and

invention in the geological and georesources engineering field in the ASEAN countries as

well as all around the world.

Respectfully Yours,

Dr. Sugeng Sapto Surjono

Head of Geological Engineering Department

Faculty of Engineering

Universitas Gadjah Mada




ii

FOREWORD

First of all, I would like to express my sincere thanks to all of you for participating in

this International Conference on Geological Engineering (ICGE) held in Yogyakarta

Indonesia, December 11–12, 2013 with the theme of “Strengthening geo-resources and

geo-engineering management for green economic growth”.

More than 12 various topics related to geological engineering are discussed during the

conference. Those consist of earth resources, exploration geosciences, environmental

geosciences, hydrogeology, slope stability, landslides susceptibility, rock mechanics,

strategic development, mineral resources, safety management, mineral processing

techniques, industrial minerals, and others that related to geo-resources and geo-

engineering aspects.

The call for papers attracted 52 submissions from 10 different countries and over 15

different institutions. The program committee accepted 42 papers that cover all of the

topics related to the georesources and geological engineering to be published in this ICGE

2013 proceeding. In addition, the program includes a panel of georesources and geological

engineering expertise from academic, governments, and industries. Hence, this conference

truly serves as an international forum for geoscientists and other stakeholders in providing

an interesting and multidimensional views, knowledge, and relevant information on

georesources and geological engineering.

Finally, we would like to thank to the AUN/SEED-Net, which initiated and support

this event and Geological Engineering Department, Gadjah Mada University as host

institution of the ICGE 2013. Thank also to the sponsorships for their support to this

conference. Special thank to the board of organizing committee, whose effort and hard

work reflecting their commitment to this conference.

Yogyakarta, December 11-12, 2013

Dr.rer.nat. Arifudin Idrus

Chief of organizing committee

ICGE 2013




iv

TABLE OF CONTENTS

Cover Page .................................................................................................................... i

Foreword ....................................................................................................................... ii

Message from Head of Geological Engineering Department-UGM ............................ iii

Table of Contents ......................................................................................................... iv

EARTH RESOURCES TOPICS

KS01 Understanding The Natural Changes of Volcano-Hosted Geothermal

System and Its Implication to The Field Development

Utami, P.,........................................................................................................ 1

ER01 Granitic Magmatism in Sulawesi Island, Indonesia; Implication for

Metallogenic Province

Maulana, A., Watanabe, K., Yonezu, K., and Imai, A., .................................. 2

ER02 Relationship Between Granitoid Types and Tin Mineralization: A Review

Of Tertiary Granitoids in Central Granitoid Belt, Myanmar

Myint, A.Z., Watanabe, K., and Yonezu, K., ................................................... 13

ER03 Geochemistry and Alteration Facies Associated with High-Sulfidation

Epithermal Mineralization At Cijulang Prospect, Garut, West Java

Tun, M.M., Warmada, I.W., Idrus,A., Harijoko, A.,

Verdiansyah, O., and Watanabe, K., .............................................................. 22

ER04 Potential of Primary Gold Mineralization Within The Upper Sungai Galas

Prospect, Gua Musang, Kelantan, Malaysia

Ariffin, K.S., Nakamura, K., Takahashi, R., Cheang, KK.,

and Zabidi,H.M., ............................................................................................ 34

ER05 Jadeite Jade from South Sulawesi in Indonesia and Its Geological

Significance

Setiawan, N.I., Osanai, Y., Nakano, N., and Adachi, T., ................................ 40




v

ER06 Magnetic Susceptibility and Mineral Exploration: Case Study of Granitic

Rocks in Cambodia

Kong, S., Watanabe, K., and Imai, A., ............................................................ 57

ER07 Geostatistics Model for Original Gas in Place (OGIP) Estimation

Muchalintamolee, N., Udomlaxsananon, P., Summapo, S.,

and Pumjan, S.,............................................................................................... 63

ER08 Sphalerites’ Mineral Chemistry and Sulphidation State of Polymetallic

Epithermal Quartz Veins at Soripesa Prospect Area, Sumbawa Island,

Indonesia

Khant, W., Warmada, I.W., Idrus, A., Setijadji, L.D., and Watanabe, K., ..... 70

ER09 Ore and Alteration Mineralogy of Muara Bungo Gold Prospect, Jambi

Province: Implication for Deposit Genesis

Hakim, F., Idrus, A., and Sanjaya, I., ............................................................. 80

ER10 Characterization of Maar Deposits from Ranu Segaran, Ranu Agung and

Ranu Katak, as Well Magmatic Evolution that Form Maar Eruption in

Tiris District, Probolinggo Regency, East Java

Prakosa, B.B., Harijoko, A., and Warmada, I.W., ......................................... 87

ER11 Ore and Alteration Mineralogy of Paningkaban-Cihonje Gold Prospect,

Gumelar Sub-District, Banyumas Regency, Central Java: A New

Discovery of Carbonate Base Metal Gold Epithermal Deposit

Idrus, A., Hakim, F., Kolb, J., Appel. P., and Aziz, M., .................................. 100

ER12 Progress on Rare Earth Elements (REE) Research in Indonesia 2008-2013

Setijadji, L.D., Warmada, I.W., Yonezu, K., and Watanabe, K., .................... 113

ER13 The Dioritic Alteration Model of The Randu Kuning Porphyry Cu-Au Ore

Deposit, Selogiri Area, Central Java, Indonesia

Sutarto., Idrus, A., Meyer, F.M., Harijoko, A., Setijadji, L.D., Dany, R., ...... 122




vi

EXPLORATION GEOSCIENES TOPICS

XG01 Potential Use of Synthetic Aperture Radar (SAR) Data for Geothermal

Exploration

Saepuloh, A., ................................................................................................... 132

XG02 Sedimentary Facies of Middle Miocene Balikpapan Formation, Samarinda

Area, Lower Kutai Basin, Indonesia

Win, C.T., Surjono, S.S., Amijaya, D.H., Husein, S., Watanabe, K.,

and Astuti, B.S., .............................................................................................. 139

XG03 “Unconventional Reservoir” Shale Gas Potential Based on Source Rock

Analysis in Sumatran Back Arc Basin

Wibowo, R.C., ................................................................................................. 151

XG04 Facies Analysis and Depositional Environments of The Ngrayong

Formation in The West Madura Area, North-East Java Basin, Indonesia

Htwe, P., Surjono, S.S., Amijaya, D.H., Sasaki. K., and Khemera. D., .......... 164

XG05 DHI Skimming, A Proposed Seismic Interpretation Technique for Quick

Reading on Speculative Hydrocarbon Fields

Zulfadli., Surjono, S.S., ................................................................................... 177

XG06 Inversion Analysis of AIGI in Seismic Data for Hydrocarbon

Identification in Sandstone Reservoir, Case Study in Mustika Field, Kutai

Basin, East Kalimantan

Asrim., Nugraha, T., Wintolo, D., and Setyowiyoto, J., ................................. 187

XG07 Relationship Between Rock Eval Pyrolysis Data and Abundance of

Liptinite Macerals in Shale of Talang Akar Formation, South Sumatera

Basin

Novianti, W., and Amijaya, D.H., ................................................................... 203




vii

ENVIRONMENTAL GEOSCIENCES TOPICS

EG01 Estimation of Strong Ground Motion in Palu, Indonesia

Thein, P.S., Pramumijoyo, S., Brotopuspito, K.S., Wilopo, W.,

Kiyono, J., and Setianto, A ., .......................................................................... 211

EG02 Seismic Microzonation of The Populated Urban Area Using Densely

Single Microtremor Observations [Case Study: Yogyakarta City-

Indonesia]

Kyaw, Z.L., Pramumijoyo, S., Husein, S., Fathani, T.F., and Kiyono, J., ...... 226

EG03 Investigation and Assessment of The Earthquake Hazards in Myanmar:

Background, Characterization, Causes, and Mitigation Measures

Kham, N.M., and Htun, K., ............................................................................. 241

EG04 Development of Seismic Microzonation Maps of Mandalay City,

Mandalay Region, Myanmar

Thant, M., Mon, C.T., Tin, T.H., Oo, K.K.K., Aung, L.T., Win, Z.M.,

Tun, N.T., Soe, M.Y., and Kawase, H., ........................................................... 258

EG05 A Sustainable Solution to Disposal Problem of Mine Tailings

Adajar, M.A.Q., and Zarco, M.A.H., .............................................................. 274

EG06 Shoreline Changes and Its Influence for Level of Coastal Vulnerability

Sirajuddin, H., Suriamihardja, D.A., Imran, A.M., and Thaha, M.A., ........... 289

GROUNDWATER AND HYDROGEOLOGY TOPICS

GH01 The Type of Water in Spring Water Hydrogeochemistry in The Eastern

Flank of Mount Merapi, Boyolali and Klaten District, Central Java,

Indonesia

Santi, N., Hendrayana, H., and Putra, D.P.E., .............................................. 299




viii

GH02 Determination of Suitable Groundwater Quality for Agriculture by Using

Gis Application, Bantul Regency, Yogyakarta Special Province, Indonesia

Kong, C., Hendrayana, H., and Setianto, A., ................................................. 304

GH03 Study on River Morphology, Gravel-Sand Depositions and Tests for Civil

Engineering Purposes, Case Study River Nam Ma, Xiengkhor, Ad and Sop

Bao Districts, Houaphanh Province

Visane, N., Sitha, and Phommasone ............................................................... 317

LANDSLIDE SUSCEPTIBILITY TOPICS

LS01 Development of A Rapid Condition Assessment Tool for Landslide

Susceptibility in The Philippines

Victor, J.A.S., and Cristobal Jr, R.A., ............................................................ 331

LS02 Community Empowerment Program of Landslide Hazard in Sepanjang

Village

Yanto, E., Andaru, A., Rudianto., Indrawan, I.G.B., and Wilopo, W., ........... 345

ROCK MECHANICS TOPICS

RM01 Piles Foundation in Phnom Penh Capital of Cambodia

Sieng, P., ......................................................................................................... 352

RM02 Strengthening Soft Soil by Electro-Kinetic Method Case Study Clayey

Soil From Ngawi Regency, East Java, Indonesia

Thuy, T.T.T., Putra, D.P.E., Budianta, W., and Hazarika, H., ....................... 371

RM03 Numerical Study of Storage Capacity and Potential Ground Uplift Due to

CO2 Injection Into Kutai Basin by Using Coupling Hydromechanical

Simulator

Arsyad, A., and Samang, L., ........................................................................... 382




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SAFETY MANAGEMENT

SM01 Threat, Hazard, Risk and Vulnerability Assessment of Merapi Volcano in

Yogyakarta, Indonesia

Brunner, I.M.I.M., and Setianto, A., ............................................................... 392

STRATEGIC DEVELOPMENT ON MINERAL RESOURCES TOPICS

SD01 Strategies for Sustainable Mining: A Case of Lead (Pb) Mining in Thailand

Boonpramote, T., ............................................................................................ 402

MINERAL PROCESSING TOPICS

KS02 Soil Reinforcement Using Calcium Phosphate Compounds

Kawasaki, S., and Akiyama, M., ..................................................................... 412

MP01 Hydrometallugical Process for Poor Zinc Oxide Ores

Dang, V.H., Dang, T.V., ................................................................................. 422

MP02 The Influence of Coal Ash Content Relating to Slagging nd Fouling on Its

Utilization as Direct Combustion

Gany, M.U.A., ................................................................................................. 430

MP03 Precursors of Coal in The Kutai Basin, East Kalimantan, Indonesia: Result

From Gas Chromatography Mass Spectrometry

Widodo, S.,...................................................................................................... 436

INDUSTRIAL MINERALS TOPICS

IM01 Carbon Dioxide Mineral Sequestration by Using Industrial Waste Gypsum

Junin, R., Rahmani, O., and Azdarpour, A., ................................................... 451

XG05 Proceedings of International Conference on Geological Engineering



177

DHI SKIMMING, A PROPOSED SEISMIC

INTERPRETATION TECHNIQUE FOR QUICK

READING ON SPECULATIVE HYDROCARBON

FIELDS

Zulfadli1, Sugeng S. Surjono

2

Geological Engineering Dept., Faculty of Engineering, Universitas Gadjah Mada

Jl. Grafika No.2. Yogyakarta, 55281, Indonesia, 1E-mail: [email protected],

2 E-mail: [email protected]

Received: November 15, 2013

Abstract

Seismic exploration for finding new hydrocarbon field is a real challenge today. Exploration

success even more crucial this day because of the greater pressure from expensive survey activities

and complex subsurface interpretations. Those issues sometimes drop the spirit to discover new

hydrocarbon fields. In order to help providing solution, we try to propose DHI Skimming. This

technique performs a quick reading of Direct Hydrocarbon Indicator (DHI) in the exploration area

covered by 3D seismic data and helps to shape the focus of exploration since early phase. DHI

Skimming particularly looks for bright spot and flat spot based on energy seismic attribute as the

earliest indicator of the hydrocarbon accumulation presence. It treats them as DHI-Energy

anomalies that predominantly associated with gas reservoirs. We introduce the concept of DHI

Skimming together with usage conditions, confirmation steps, and the interpretation result on

Dutch Offshore F3 Block, North Sea.

DHI Skimming successfully detected existence of eight speculative fields and a regional

distribution of deeper potential reservoir. Seismic structural interpretation found some faults as

structural controls on several fields indicated the presence of hydrocarbon migration path.

Advanced seismic interpretation tested one of the speculative fields with some confirmation

techniques, which showed consistency in the prospective values. These results demonstrate the

effectiveness of speculative hydrocarbon fields detection using DHI Skimming. This technique is

able to provide early anticipation for subsurface uncertainty and to strengthen decision making in

order to avoid exploration failures.

Keywords: Direct Hydrocarbon Indicator, Seismic Attributes, Speculative Hydrocarbon Field

Introduction

Southeast Asia holds significant prospect of undiscovered hydrocarbon resources together

with its risk. An assessment within 23 geologic provinces in Southeast Asia finds that more

than 90 percent of undiscovered resources are offshore, and there are more than twice of

undiscovered gas resources (49,794 MMBOE) than undiscovered oil resources (21,632

MMBO) [1]. Those opportunities are transformed into some exploration changes

correlated with major industry investment: 1) exploration trend shifts from well-explored

areas to least-explored areas, 2) exploration activities move from onshore to offshore

(including deep-water), and 3) exploration target changes from oil to gas [2]. Nonetheless,

these huge opportunities are also accompanied by trembling challenges. In Indonesia, some

major players tapped to very expensive deep-water projects decided to return their blocks

after discovering their exploration wells turned out to be dry holes [3]. This fact reflects




178

that geological complexity of subsurface [4] can be very challenging for any exploration in

the least-explored area to become a successful discovery. This situation needs new

solutions to deal with the problems of subsurface uncertainty for exploring new petroleum

fields.

A very common way to observe the prospect of any seismic exploration area is by

looking for anomalies in seismic amplitude. Direct Hydrocarbon Indicator (DHI) is

important seismic amplitude phenomena, especially bright spot and flat spot, related with

presence of hydrocarbon accumulation and reservoir detection [5,6,7,8]. DHI commonly

relates to gas rather than oil reservoirs because the effect on acoustic properties of gas in

the pores is greater than oil [5]. The problem of using DHI comes from the facts that not

only hydrocarbon accumulations can be represented by amplitude anomalies as bright

spots and they may lead to dry holes drilling [5,6,8]. This problem is solved by some

confirmation/validation steps to ensure the DHI truly represents oil or gas reservoirs, in

form of question lists or additional techniques [6,8].

Figure 1. Netherlands geographical and geological map showing location of 3D seismic

survey on F3 Block as the data for this study [9,10, with minor modification].

We propose DHI Skimming to help solving the prospect identification problem at least-

explored areas and ambiguous representation problem of DHI. We introduce DHI

Skimming as a technique to do quick reading of DHI to shape the prospective focus of

exploration area covered by 3D seismic data. We equip this technique with some

confirmation steps to ensure the skimming result is related with hydrocarbon accumulation.

We tested this technique on Dutch Offshore F3 Block 3D seismic dataset (Figure 1) to

provide open opportunity for anyone to review our idea freely. We hope this technique can

be applied in Southeast Asia for increasing successful ratio of new petroleum field

(Wong, et al., 2007; Schroot & Schüttenhelm, 2003; with minor modification)




179

exploration in the future. This publication will focus on discussing concept of DHI

Skimming together with its usage conditions, confirmation steps, and the result on F3

Block.

DHI Skimming

Concept

DHI Skimming allows enhancement of seismic data visualization by running energy

attribute as pre-identification tool for detecting speculative hydrocarbon fields. This

seismic attribute can be used to perform a quick reading of energy related with seismic

amplitude anomalies to characterize acoustic rock properties and bed thickness [11].

Energy attribute calculates the squared sum of the sample values in the specified time-gate

divided by the number of samples in the gate [11]. Without need to consider the positive-

negative signs, we can find that the higher the amplitude values, the higher the energy

values. Since seismic amplitude relates with DHI [5,6,7,8,10], then energy attribute

reading can be correlated to DHI too. We call the result of DHI Skimming as DHI-Energy

objects, either in 2D profiles or 3D geobodies. This is the basic concept of DHI Skimming.

The difference between DHI from common seismic amplitude observation and DHI-

Energy from DHI Skimming happens on capability of reservoir separation (Figure 2a and

2b). DHI Skimming only finds the reservoir without knowing its layers as detail as

common DHI observation. The positive side of using DHI Skimming is its capability to

rapidly scan entire seismic data as quantitative approach that can be confirmed multiple

times later. DHI Skimming also provides opportunity to directly model the DHI-Energy in

form of geobody objects relate with potential reservoirs (Figure 2c). Together with its

usage conditions and confirmation steps, the superiority of DHI Skimming can be useful

for increasing awareness to anticipate speculative prospects, focusing exploration targets in

more detail, avoiding further exploration failures, and hopefully shortening exploration

phase.

Figure 2. Visual comparison of (a) common DHI profile, (b) 2D DHI-Energy profile, and

(c) 3D DHI-Energy geobody. The DHI-Energy object is the DHI Skimming detection

result.

Common DHI profile DHI-Energy in 2D profile DHI-Energy in 3D geobody

a b c




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Usage conditions

We propose DHI Skimming on several usage conditions based on standard requirement

from some references and our test on F3 Block 3D seismic dataset. The usage conditions of

DHI Skimming cover some aspects as follow:

Seismic data setting:

DHI Skimming needs zero-phased 3D seismic data (inferred from [5,6])

Confirmation steps:

DHI Skimming result extremely needs to be confirmed (inferred from [5,6,8])

Availability of additional data:

DHI Skimming needs well logs data (even from dry holes) for going through

advanced confirmation steps

Early detection:

DHI Skimming is intended to do early detection only. It can not replace advanced

reservoir characterization methods (e.g. AVO analysis, core analysis)

Confirmation steps

We equip DHI Skimming with some confirmation steps to ensure the results directly

represent hydrocarbon accumulations. The confirmation steps consist of two main parts i.e.

standard and advanced confirmations. Standard confirmation steps verify the DHI-Energy

objects are hydrocarbon accumulations by investigating connectivity of fault and presence

of some DHI types (i.e. bright spot, flat spot, and polarity reversal). Advanced

confirmation steps verify the DHI Skimming result by using spectral decomposition,

seismic inversion, and neural network porosity inversion. The idea of those confirmation

steps are developed from some confirmation questions for common DHI observation [6]

and available techniques to study seismic reservoirs [5,11,12].

This publication will discuss the application of standard confirmation steps dominantly.

The advanced ones will be explained in concise way only. Table 1 shows the list of

confirmation steps for verifying DHI Skimming result.

Table 1 Confirmation Steps to Verify DHI Skimming Result

Confirmation Types Steps

Standard Confirmation Finding fault connecting two reservoirs

Finding bright spot, flat spot, and polarity reversal in a reservoir

Advanced Confirmation

Applying spectral decomposition on the reservoir

Applying seismic inversion on the reservoir

Applying neural network porosity prediction on the reservoir

The standard confirmation steps begin with finding fault as hydrocarbon migration path

[5,6]. This fault should be clearly connected with two different level reservoirs (deeper vs.

shallower) to ensure it is really eligible as hydrocarbon migration path. In this fault

confirmation step, we need to define the fault, two reservoirs on different level as DHI-

Energy objects (preferably in 3D geobodies), and their clear connectivity based on seismic

data structural interpretation.

The next standard confirmation step is to completely find three DHI types in one

reservoir. They are bright spot, flat spot, and polarity reversal. Bright spot is responsible to

show hydrocarbon presence, especially gas [5,10]. Since bright spot is non-unique




181

indicator, we need to find flat spot to make a better confirmation [5,6,8]. Flat spot is more

powerful than bright spot because it can show the unique character of fluids i.e. flat

hydrocarbon-water contact [5,8]. Flat spot also relates with good reservoir thickness [5], so

it can also indicate economic potential of the reservoir. We can still ensure more by finding

polarity reversal. Polarity reversal can be correlated with situation where water sand has

higher acoustic impedance than the embedding shales [5]. This is very important indicator

because we can surely know that our reservoir contains hydrocarbon and water, which

confirms DHI Skimming really detected petroleum accumulation. This DHI types finding

step will be ideally useful in Tertiary clastics (inferred from [5]).

The advanced confirmation steps allow specific examinations on reservoirs that passed

standard confirmations. Spectral decomposition will be able to reveal stratigraphic and

reservoir intricacies [5]. Seismic inversion will be able to construct acoustic impedance

variation in the subsurface [6,12] allowing easier interpretation on reservoir layers and

building relationship to porosity [5]. Neural network porosity prediction will be able to

construct porosity volume and study the reservoir characteristic [11].

Figure 3. DHI Skimming detected DHI-Energy anomalies on F3 Block 3D seismic dataset.

The result of DHI Skimming showed 8 speculative reservoirs on Upper North Sea Group

(green geobodies) and 1 regional potential reservoir on Chalk Group (yellow geobody).

Results and Discussions

DHI Skimming result

The result of DHI Skimming on Dutch Offshore F3 Block 3D seismic dataset showed eight

speculative reservoirs and a regional distribution of deeper potential reservoir in form of

DHI-Energy geobodies (Figure 3). In this stage, we used DHI Skimming to read entire

= DHI-Energy geobodies on Upper North Sea Group

= DHI-Energy geobody on Chalk Group

Tulip Alpha

Tulip Sigma

Tulip Sigma




182

seismic data for finding significant energy anomalies and then we converted them into

speculative reservoir geobodies. The eight speculative reservoirs were detected on Upper

North Sea Group, and the deeper regional potential reservoir was on Chalk Group. Chalk

Group has hydrocarbon play dominated by oil, and hydrocarbon play for Upper North Sea

Group is dominated by gas [13,10].

We selected the biggest reservoir on Upper North Sea Group and named it “Tulip

Alpha”. We also named the regional potential reservoir on Chalk Group as “Tulip Sigma”

(Figure 3). Our target reservoir in this publication is Tulip Alpha. We will test it by using

standard and advanced confirmation steps to examine whether this DHI Skimming result

really correlates with hydrocarbon accumulation or not.

Standard confirmation steps

The first standard confirmation step is finding fault that connecting two reservoirs. Our

target reservoir in this publication is Tulip Alpha, and another reservoir to pair with is

Tulip Sigma as a deeper one. We found a regional normal fault connecting Tulip Sigma to

Tulip Alpha on this standard confirmation step (Figure 4). This confirmation step passed

Tulip Alpha as a speculative reservoir that has hydrocarbon migration path and direct

connection with other reservoir.

This first confirmation step ensured that Tulip Alpha has a historical connection with

Tulip Sigma through the normal fault. Since both of them show good DHI-Energy

anomalies, then we can increase our confidence to decide that these reservoirs have greater

probabilities containing hydrocarbon accumulations.

Figure 4. Standard confirmation step on DHI-Energy profiles by finding connecting fault

between Tulip Alpha and Tulip Sigma. A regional normal fault (green curve) is found and

clearly observed on seismic data connecting the reservoirs.

Tulip Alpha

Tulip Sigma

Tulip Sigma




183

The second standard confirmation step is completely finding three DHI types on Tulip

Alpha as our target reservoir. The three DHI types are bright spot, flat spot, and polarity

reversal. We found all of them on this standard confirmation step at Tulip Alpha. This

confirmation step passed Tulip Alpha as a speculative reservoir that has confirmed

qualitative DHIs relate with potential hydrocarbon accumulation.

This second confirmation step ensured that Tulip Alpha fulfills the requirement to

become a hydrocarbon reservoir based on tight qualitative observation at its amplitude

anomalies. Besides the presence of bright spot, we also found flat spot and polarity reversal

on Tulip Alpha. Flat spot presence indicates this reservoir is thick enough, so we can think

that Tulip Alpha is an economic reservoir regarding its thickness (inferred from [5]).

Polarity reversal presence indicates there is fluids lateral change on this reservoir, so we

can think that Tulip Alpha has greater probability contains water and hydrocarbon (inferred

from [5]). The result of second standard confirmation step on Tulip Alpha is shown on

Figure 5.

Figure 5. Standard confirmation step on DHI-Energy profile by completely finding bright

spot, flat spot, and polarity reversal on Tulip Alpha. Those three DHI types are

successfully found by using qualitative observation on seismic data.

Advanced confirmation steps

Advanced confirmation steps on Tulip Alpha consist of applying spectral decomposition,

seismic inversion, and neural network porosity prediction. All of these steps examine Tulip

Alpha based on frequency response to hydrocarbon presence, acoustic impedance of

petroleum-filled reservoir, and its predictive porosity value (Figure 6).

We used Continuous Wavelet Transform (CWT) as the spectral decomposition

technique on Tulip Alpha. The result on low frequency showed that Tulip Alpha has strong

indicator to be a hydrocarbon reservoir, based on hydrocarbon attenuation effects. The

Bright spot

Flat spot

Polarity reversal




184

result also showed that eastern part of Tulip Alpha is more prospective than its western

part (Figure 6a).

Figure 6. The results of advanced confirmation steps on Tulip Alpha as DHI-Energy

profile by doing (a) CWT spectral decomposition, (b) seismic colored inversion, and (c)

neural network porosity prediction. These confirmation steps consider Tulip Alpha as a

prospective reservoir on Dutch Offshore F3 Block.

a

b

c




185

We used Seismic Colored Inversion (SCI) to get acoustic impedance value on Tulip

Alpha. The result showed the clear layering of Tulip Alpha that relates with fluid contents.

The result also showed distinct separation between this reservoir and its non-reservoir

environment around it (Figure 6b).

We used supervised neural network to do porosity prediction on Tulip Alpha. The

result showed a very good porosity value of Tulip Alpha i.e. 35-40% (Figure 6c). This

porosity prediction step gave a great closure of confirmation steps on Tulip Alpha as one

of DHI Skimming result.

All of those advanced confirmation steps passed Tulip Alpha as a prospective reservoir

in Dutch Offshore F3 Block. This final result confirmed Tulip Alpha, as one of DHI-

Energy objects from DHI Skimming, is strongly correlated with hydrocarbon

accumulation. This result also proved effectiveness of DHI Skimming and its confirmation

steps to do a quick reading on speculative hydrocarbon fields.

DHI Skimming is intended to be a tool for early detection of speculative prospects

only. The strength of using DHI Skimming is its capability to scan entire seismic data and

to quickly reveal speculative reservoirs as DHI-Energy anomalies in there. Although the

result of DHI Skimming and its confirmation steps are really good, they still can not be

considered as final exploration decision directly.

Conclusion

DHI Skimming as a proposed seismic interpretation technique for speculative hydrocarbon

fields quick reading successfully found eight speculative reservoirs and one regional

distribution of deeper reservoir from the seismic data. This preliminary findings

demonstrated detection effectiveness of DHI Skimming.

DHI Skimming came with its usage conditions and some confirmation steps to ensure

the result is reliable and directly correlates with hydrocarbon accumulation. There are

standard and advanced confirmation steps to examine DHI-Energy objects from DHI

Skimming. We tested Tulip Alpha as one of speculative reservoirs from DHI Skimming by

using all confirmation steps. The confirmation steps passed Tulip Alpha as a prospective

reservoir on Dutch Offshore F3 Block. This result showed capability of DHI Skimming to

help solving prospect identification problem on least-explored areas and ambiguous

representation problem of DHI.

This technique can be really useful to manage uncertainty and risk on exploration

phase. The successful identification using DHI Skimming on this study can be re-applied

in other hydrocarbon exploration areas or blocks, including at Southeast Asia that holds

significant prospect of undiscovered hydrocarbon resources.

References

[1] USGS, Assessment of Undiscovered Oil and Gas Resources of Southeast Asia, 2010,

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