RESERVOIR CONNECTIVITY STUDY OF G057B & G058B ZONES IN NILAM FIELD, KUTEI BASIN,

EAST KALIMANTAN

T H E S I S MAGISTER PETROLEUM GEOLOGY

By:

Hendri Harsian

22006029

SEKOLAH PASCA SARJANA

MAGISTER TEKNIK GEOLOGI BANDUNG INSTITUTE OF TECHNOLOGY

2009

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APPROVAL SHEET

RESERVOIR CONNECTIVITY STUDY OF G057B & G058B ZONES IN NILAM FIELD, KUTEI BASIN,

EAST KALIMANTAN

T H E S I S

As an academic purpose for magister petroleum geology program at

Sekolah Pasca Sarjana, Magister Teknik Geologi Bandung Institute of Technology

By :

Hendri Harsian NIM. 22006029

Thesis Advisor

DR. Ir. Dardji N.

ABSTRACT

In a mature field integrated approach is necessary, especially if various kinds of data are available. Consentino (2001) proposed an integrated approach on reservoir heterogeneity (connectivity), that the reservoir connectivity can be studied by integration of geophysics, fluid data, well testing and production data. While Snedden et al. (2007) proposed the static and dynamic approach in studying reservoir connectivity. These approaches tried to be applied in the reservoir connectivity study of G057B and G058B sand in Nilam Field, Kutei Basin, East Kalimantan, Indonesia.

Nilam Field is part of Sanga Sanga PSC where VICO Indonesia operates and already reached mature stage as a gas field. Production started from 1974 and today more than 250 wells have been drilled and to date the production already reach 3.5 TCF gas. Reservoir model have been develop since exploration stage, but as new data gathered this model have to be updated and revised.

Reservoir connectivity study of G057B and G058B started by remapping and building its geological model. Sequence stratigraphy approach applied in remapping the stratigraphy of both sands. G057B and G058B are channel fill and bars deposits in upper deltaic depositional environment. Both facies interpretation base on open hole log data, except G057B facies interpretation supported by core analysis from NLM0600.

Seismic 3D, gas chromatography analysis result and permeability data from ELAN Volume analysis were integrated to geological model. Unfortunately, due to lack of data quantity and quality, the optimum result couldn’t be reach for reservoir connectivity of G057B and G058B sands from the integration.

Pressure data from RFT/MDT and production data analysis then used in integration with geological model and help in refining reservoir connectivity definition of G057B and G058B sands. As the result 11 reservoirs (tanks) defined for G057B and 14 reservoirs (tanks) defined for G058B. Reservoir distribution of both sands plotted in reservoir connectivity maps.

The geological model of reservoirs derived from net sand distributionis not consistent with reservoir connectivity distribution based on integrated study result. This probably due to diagenetic control in NIlam Field which taken place after the deposition, as shown by calcareous nodules and well-cemented sandstones.

At the end, found that dominant contribution for reservoir connectivity distribution of G057B and G058B sand in Nilam Field were geological model and pressure trend analysis result. Then its recommended to do further study if other data supporting the reservoir connectivity are available.

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ABSTRAK

Pada tahap mature stage dari suatu lapangan minyak pendekatan yang terintegrasi adalah

sangat penting untuk dilakukan, terutama jika bermacam data sudah tersedia. Consentino

(2001) mengusulkan bahwa hubungan konektivitas reservoar bisa dipelajari dari integrasi data

geofisika, data analisa fluida, data uji sumur (well test)dan data-data produksi. Sementara

Snedden et al. (2007) mengajukan pendekatan secara statik dan dinamik dalam mempelajari

hubungan konektivitas reservoar. Kedua pendekatan ini lalu di coba untuk diterapkan pada

zona G057B dan G058B di Lapangan Nilam, Cekungan Kutai, Kalimantan Timur, Indonesia.

Lapangan Nilam adalah bagian dari Sanga Sanga PSC dimana VICO Indonesia beroperasi dan

telah berada di tahap mature sebagai sebuah lapangan minyak dan gas bumi. Produksi

pertama kali dilakukan pada tahun 1974 dan sampai hari ini telah mempunyai sebanyak 250

lebih sumur dan produksinya telah mencapai 3.5 TCF gas. Pemodelan reservoar juga sudah

dilakukan sejak tahap awal explorasi, tetapi dengan bertambahnya data model tersebut harus

selalu di perbaharui dan di koreksi.

Studi hubungan konektivitas reservoar G057B dan G058B diawali dengan pemetaan ulang

(remapping) dan pembuatan model geologi. Pendekatan sekuen stratigrafi dipergunakan

didalam pemetaan ulang kedua zona tersebut. G057B dan G058B adalah endapan sungai

(channel fills) dan endapan gosong pasir (bars) yang terendapkan di lingkungan pengendapan

upper delta plain. Pemerian facies G057B dan G058B didasarkan pada data log sumur (open

hole logs), dan untuk G058B didukung juga oleh data inti bor (core) dari sumur NLM0600.

Seimik 3D, hasil analisa gas chromatography dan permeability hasil dari analisa ELAN Volume

juga dicoba dintegrasikan dengan model geologi yang telah di dapat sebelumnya. Tetapi,

karena kurangnya kuantitas dan kualitas dari data-data tersebut, hasil yang optimal tidak bisa

didapatkan dalam hal mengtahui hubungan konektivitas reservoar G057B dan G058B.

Data tekanan (pressure) dari RFT/MDT serta data produksi kemudian di gabungkan dengan

model geologi dan membantu dalam hal mengetahui hubungan konektivitas dari G057B dan

G058B. Sebagai hasilnya, 11 reservoar (tanks) di interpretasikan untuk G057B dan 14 reservoar

(tanks) di interpretasikan untuk G058B. Hasil hubungan konektivitas tersebut lalu di gambarkan

didalam peta hubungan konektivitas reservoar.

Model geologi awal yang di kembangkan dari net sand data menperlihatkan hasil yang tidak

konsisten dengan hubungan konektivitas reservoar yang dihasilkan dari hasil studi integrasi. Hal

ini mungkin terjadi karena adanya proses-proses diagenesa yang terjadi di Lapangan Nilam,

sebagai contoh adanya ditemukan nodul calcareous dan batupasir yang well-cemented.

Pada akhirnya, disimpulkan bahwa model geologi dan pola data tekanan memberikan

kontribusi yang dominan terhadap distribusi reservoar di zona G057B dan G058B. Juga lalu

direkomendasikan untuk melakukan studi lebih jauh jika data-data baru yang mendukung

sudah tersedia.

ACKNOWLEDGMENTS

One thing that we have to remember in life is that we have to finish what we have started. So, I am glad that by finishing the writing of this thesis also mean that I have finish one thing that I have started.

My thanks start with Bpk. Dardji N. as my thesis supervisor, especially for his times and his guidance in helping me during this study. Bpk. Imam A.S. as head of geology master degree program for his understanding and ‘logic’ style management. Pak Ade for his help on administration and paper-work.

Also, thank you for VICO Indonesia team, Adde Avrino and Teguh Nugraha for geophysical ‘contribution’, Harry Alam for his help in general and Mas Amireno for his support and ideas. Thank you to Chrisnadi, Sutha and Mbak Nora for their Landmark quick learning session. Also thank you to management of VICO Indonesia for allowing me to do this work and giving me some spare times to work on this study.

Special thank you for my wife Luli for always ‘being there’, and the rest of the family for bring me up to this stage of my life. Especially, for my father Harmen Amran who keeps inspiring me about how to live in this world with his thoughts during my childhood times.

Jakarta, early April 2009

Hendri Harsian

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TABLE OF CONTENTS

Chapter Page

Approval Sheet…………………………………………………………………………......................... i

Table of Contents………………………………………………………………………………………………. ii

List of Figures……………………………………………………………………................................. iv

I.Introduction……………………………………………………………………………………………………. 1

I.1. Background………………………………………………………………………………………………… 1

I.2. Problem Definition…………………………………………………………………………………….. 2

I.2.1. Subject of Study…………………………………………………………………………………. 2

I.2.2. Object of Study………………………………………………………………………………….. 2

I.3. Scope of Study…………………………………………………………………………………………… 2

I.4. Hypothesis……………………………………………………………….................................... 2

I.5. Assumptions……………………………………………………………………………………………… 2

II. Geology of Study area…………………………………………………………………………………… 3

II.1. Regional Geology…………………………………………………………………….……………….. 3

II.2. Nilam Field…………………………..…………………………………………………….…………….. 5

III. Methodology………..……………………………………………….……………………….…………... 6

III.1. Reasoning Methodology………………………………..………………………….…………….. 6

III.2. Background Theory of Reservoir Heterogeneity (Connectivity)….……………. 6

III.3. Data Collection..…………………………………………………………………………….……….. 10

III.4. Data Processing…………………………………………………………………………….………… 10

III.5. Data Analysis……………………………..………………………………………………….………… 10

IV. Reservoir Connectivity Analysis…………………..…………………………………….………… 13

IV.1. Stratigraphy Analysis………….…….………………………………………………………….…… 13

IV.2. Geophysical Analysis……………….…………….…………………………………………….…… 22

IV.2.1. Data Availability and Quality…………………………………………………………… 22

IV.2.2. Seismic Interpretation……………………………………………………………………. 22

IV.3. Reservoir Property Analysis……………………….………………………………………….… 26

IV.4. Fluid and Production Data Analysis ………….…………………………………………….. 29

IV.4.1. Fluid Data Analysis………………..……………………………………………………….. 29

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IV.4.2. Pressure Data Trend Analysis…………………………………………………………. 31

V. Results………..…………………………..………………………………………………………………….. 40

VI. Discussion and Conclusion………………..……………………………………………………….. 49

VII. References…………………………………………………………………………………………………

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LIST OF FIGURES

Figure 1. Simplified geological map of Kutei Basin and Nilam Field location. (Modified from Payenberg et al., 2003).

Figure 2. Chronostratigraphy of Kutei Basin and surroundings. (Ferguson et al., 2000).

Figure 3. Tectonic map of Kutei Basin and surroundings. (Ferguson et al., 2000)

Figure 4. Field distribution map of Sanga-sanga PSC (Butterworth, 2001)

Figure 5. Well location map of Nilam Field.(Source VICO Indonesia, 2007)

Figure 6. Classification of reservoir heterogeneity.(Cosentino, 2001)

Figure 7. General workflow of the study.

Figure 8. Example of seismic attribute analysis (amplitude attribute analysis) used for reservoir connectivity study. Red line is interpreted border of fluvial channel system represent a reservoir. .

Figure 9. Example of star plot of gas chromatography data analysis from reservoir A and reservoir B, showing different gas chromatography results as those two reservoirs are separated.

Figure 10. Example of correlation analysis for reservoir connectivity study.

Figure 11. Example of pressure decline trend analysis of two reservoirs in presence of two decline trends. (Cosentino, 2001)

Figure 12. Example of reservoir connectivity map resulted from geological correlation.

Figure 13. Cross section line basemap of study area.

Figure 14. Delta classification based on the types of processes which control sediment transport as proposed by Gallaway (1975). Allen et al. (1989), interpreted that Mahakam delta affected by very low energy and mixture of fluvial and tidal processes, as plotted in the figure above.

Figure 15. Typical coarsening upward profile of a prograding deltaic sequence. (modified from Allen et al., 1989)

Figure 16. Section showing multiple deltaic sequences from G059 coal up to G053 coal.

Figure 17. Other section showing multiple deltaic sequences from G059 coal up to G053 coal.

Figure 18. Logs and ELAN volume (logs mineralogy volume analysis) result with core description of G057B from NLM0600.

Figure 19. Logs and ELAN volume (logs mineralogy volume analysis) result of G058B from NLM1450.

Figure 20. Reservoir map based on geological analysis for G057B sand. Figure 21. Reservoir map based on geological analysis for G058B sand. Figure 22. Map of seismic 3D lines from Nilam Field, with well location. Figure 23. Plot amplitude spectrum of seismic 3D from Nilam Field. Figure 24. West – East (sec#AB) seismic section from southern part of Nilam field,

showing Nilam anticline but no fault. Figure 25. North – south (sec #CD) seismic section from Nilam Field 3D seismic data. Figure 26. West – East (sec#GH) seismic section from center part of Nilam field,

showing Nilam anticline but no fault as reservoir connectivity control.

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Figure 27. Contour plot permeability value of G057B sand (red line). Permeability value derived from ELAN Volume analysis. Green lines represent contour structure.

Figure 28. Contour plot permeability value of G058B sand (red line). Permeability value derived from ELAN Volume analysis. Green lines represent contour structure.

Figure 29. Reservoir connectivity map of G058B sand with wells with gas chromatography analysis.

Figure 30. Pressure decline plot of G057B tank03, tank04 and tank05, northern to middle part of Nilam Field. Only one recorded data from tank04 found and its showing less pressure then virgin initial pressure, probably due to producing from adjacent well(s) which the pressure record not found. Tank05 and tank03 showing a good pressure trend decline curve as the wells position in related cluster.

Figure 31. Pressure decline plot of G057B tank05 and tank06, northern to middle part of Nilam Field. Only one recorded data from tank06 found and its showing virgin initial pressure, probably due to never been produced from adjacent well(s). Tank05 pressure decline showing relatively good pressure trend decline curve as the wells position in related cluster.

Figure 32. Pressure decline plot of G057B tank06, tank07 and tank08, in the center part of Nilam Field. Only one recorded data from tank06 and tank08 found and these showing virgin initial pressures. Tank07 pressure decline showing relatively good pressure trend decline curve as the wells position in related cluster.

Figure 33. Pressure decline plot of G057B tank09, tank10 and tank11, pressure in tank10 remain high because this tank never been produced. While tank11 only have one RFT data recorded and already showing decline pressure value from virgin initial pressure. Tank9 decline trend pressure showing a good relationship as production from the tank started in 1990s.

Figure 34. Pressure decline plot of G058B tank02 and tank03, all RFT pressure recorded still in initial pressure. No further pressure data from adjacent well recorded, only some BHP pressure which difficult to interpret because recorded commingle with other production zones.

Figure 35. Pressure decline plot of G058B tank03, tank04 and tank06. Only one pressure data recorded from tank06, which lead to separate the tank from the adjacent tank due to different trend. Tank03 quite big but still have a good decline trend which different with trend of tank04 as it’s adjacent.

Figure 36. Pressure decline plot of G058B tank07, tank08 and tank09. Only one pressure data recorded from tank07 and it’s difficult to differentiate with adjacent tank because no trend can be plot. Tank08 and tank09 are big but still have good decline trends which differentiate between the two tanks.

Figure 37. Pressure decline plot of G058B tank11, tank12 and tank13. Three decline pressure trends showing in the analysis reflecting different reservoir tanks althought the three tanks position are close each other.

Figure 38. Stratigraphy correlation of G057B sand, showing tank07 and Tank08 which separated after pressure trend analysis result

Figure 39. Zoom reservoir maps of G057B sand based on geological analysis result (left) compare with after pressure trend analysis result (right) and CD cross

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section line from previous page. Figure 40. Stratigraphy correlation of G058B sand, showing tank05 and Tank03

which separated after pressure trend analysis result. Figure 41

Zoom reservoir maps of G058B sand based on geological analysis result (left) compare with after pressure trend analysis result (right) and N-S cross section line from previous page.

Figure 42

Comparison of reservoir connectivity maps of G057B resulted from geological analysis only (left) and after integrated with pressure trend analysis result (right).

Figure 43

Comparison of reservoir connectivity maps of G058B resulted from geological analysis only (left )and after integrated with pressure trend analysis result (right).

Figure 44

Reservoir map based on integrated study of reservoir connectivity for G057B sand.

Figure 45

Reservoir map based on integrated study of reservoir connectivity for G058B sand.

Attachments Reservoir Connectivity Map of G057B

Reservoir Connectivity Map of G058B

Reservoir Connectivity by Geological Analysis Map of G057B

Reservoir Connectivity by Geological Analysis Map of G058B

Reservoir Connectivity & ELAN Permeability Map of G057B

Reservoir Connectivity & ELAN Permeability Map of G058B