Muglad basin reservior charactarization.pptx

This topic is apart of PhD project deals with sedimentology and reservoir characterization. The data for this work are from Sudan, include cores, wireline logs and well cuttings. The result of this work is well presented in the power point.

1. SEDIMENTOLOGY AND RESERVOIR CHARACTERIZATION OF BENTIU FORMATION (ALBIAN-CENOMANIAN) HEGLIG OIL FIELD MUGLAD BASIN SE SUDAN Supervisor: Assoc. Prof. Dr. Abdul Hadi Abd Rahman Co-Supervisors: Assoc. Prof : Wan Ismail Wan Yusoff, Dr. Ahmed M. Salim Field Supervisor : Dr. Jamal Ragab DEPARTMENT OF GEOSCIENCES By AHMED ALI HASSAN TAHA “PhD Candidate” Research complication seminar - 13 June 2016

2. Presentation outlines

3. 3 Sudan the third largest country in Africa Situated in NE corner of the continent Unique position Sharing borders with seven countries plus the Red Sea in the NE Beside the Unique position Sudan is very rich in natural resources. Most important hydrocarbon accumulation discovered in the last three decades

4. 4 Muglad basin Heglig field SE sector NW sector Study Area West and central African rift system modified after ( Fairhead 1988 ) Location and trend of the Muglad Basin and Heglig oil field (modified afte r Mohammed et al., 1999, Yousif M. Makeen et al., 2015 ) Hydrocarbon found mainly in the interior rift basins of Sudan of which Muglad basin is largest and most important Muglad basin is one of the late Jurassic (?) – Cretaceous central African rift system (CARS) (Schull 1988 ) Number of field discovered in Muglad basin in 70s & 80s of the last centaury (Unity , Heglig, Bamboo , Neim , etc.) Location of the study area Heglig is second largest oil field in Muglad basin and the largest in Sudan discovered by Chevron 1982

5. 5 Muglad basin is largest interior rift basin in Sudan formed due to tectonic activity as a part of CARS ( Schull , 1988 ), The sedimentary infill the basin ranges from fluvial origin to lacustrine origin. Three rift phases were responsible for the deposition of thick non-marine sediments within the basin (13 Km ) ( Mchargue et al 1992 ), Heglig oil field is the second largest oil field in Muglad basin and the largest in Sudan discovered by Chevron in 1982, The sandstone of Bentiu formation is the main reservoir in Muglad basin and Heglig oil that demonstrate a significant degree of Heterogeneity at different scales , Mchargue , T. R., T. L. Heidrick and J. E. Livingston (1992). " Tectonostratigraphic development of the interior Sudan rifts, Central Africa." Tectonophysics 213(1-2): 187-202. Schull , T. J. (1988). "Rift basins of interior Sudan: petroleum exploration and discovery." AAPG bulletin 72(10): 1128-1142. Previous work

6. 6 Understanding the lithofacies and stratigraphic setting , depositional environment , architecture elements, reservoir characteristics and geometry are the main challenges due to lack of detailed studies, Complexity of the depositional staked-pattern, structural framework and reservoir characteristics are poorly understood this initiate necessities for further studies. This study was carried out to integrate sedimentology with petrophysics to reveal the reservoir characteristics, architecture and heterogeneity. An integrated reservoir characterization approach using sedimentology techniques and petrophysical tools was applied.

7. 7 The Albian-Cenomanian Bentiu formation is main oil producing reservoir in the basin, It is dominated by channel sandstone and shale that deposited in fluvial environment at the end of first rifting phase which demonstrate significant degree of heterogeneities in different scales T he stratigraphic units, of the Muglad Rift Basin, SW Sudan, their lithology and depositional environment (Adopted from ( Schull 1988 ); after ( Sayed 2003 ) Stratigraphy of Muglad basin

8. 8 Problem statement Heglig oil field is the second-largest oil field on Muglad basin, “after the Unity field." and the largest discovery in Sudan. The field was discovered by Chevron overseas in 1982. It starts producing in 1999, when the Greater Nile Petroleum Operating Company ( GNPOC ) a consortium of companies from China, Malaysia, India and Sudan operates the field. The field reaches its peak production point in 2006. Hydrocarbons of Heglig oil field is found mainly in sandstone reservoir of Bentiu formation. Little detailed reservoir characterization work has been done in the field. Understanding the lithofacies and depositional environment, stratigraphic setting, architecture elements within Heglig oil field and reservoir quality of the cored succession and extrapolating the result to the uncored intervals, will help in understanding the whole reservoir characteristics, and it will contribute to improvement of the field recovery and future field development.

9. 9 To evaluate the sedimentary facies, depositional environment and reservoir characteristics of cored succession. To construct the stratigraphic architecture of the Albian – Cenomanian succession of the Heglig oil field. To propose the relationship between the sedimentary facies and reservoir quality of the Albian – Cenomanian succession of the Heglig oil field. Objectives: of the study can be summarized as follows:

10. Core wells Dataset: Well name Core 1 length Core 2 lengths Core 3 lengths Total length HE 28 8.30 m (1635.12-1643.43) 10.33 m (1644.00-1654.33) 8.1 m (1654.33-1662.40) 20.73 m HE 38 2.12 m (1632.12-1634.28) 11.00 m (1638.00-1649.50) 9.3 m (1649.5-1660) 22.42 m HE 52   10.00 m (1872.00-1882.00)   10.00 m Summary of the cored intervals from the selected wells Base map showing wells location. Cored wells are indicated by red circles. The selected study area consist of 10 wells. Conventional cores from 3 wells Wireline logs sample Materials and dataset Core sample Cutting sample Drill well cuttings from 10 wells Wireline logs sets from 10 wells Daily drill well report

11. Reservoir Characterization Petrography: Thin Sections Point counting Scanning Electron Microscopy Energy Dispersive X-Ray Porosity Permeability Water Saturation Petrophysical properties: Porosity Permeability Water Saturation

12. Work-Flow chart 12

13. Core description and facies analysis Nine lithofacies described and analyzed Facies, grain sizes, sedimentary structures and depositional processes Graphic representation of facies from cores obtained from 3 wells NW SE HE 52 (1 ) HE 28 (1 ) HE 28 ( 2) HE 28 (3 ) HE 38 (1 ) HE 38 (1 ) HE 38 (3) Siltstone Massive Sandstone Cross stratified sandstone Trough stratified sandstone Horizontal stratified sandstone Ripple stratified Low angle stratified Mudstone Conglomerate

14. 14 Core facies Massive sandstone Planar cross bedded sandstone Trough cross bedded sandstone Parallel cross bedded sandstone Ripple laminated sandstone A B A B A B B A Low angle cross Siltstone Mudstone layered and massive Conglomerate stratified sandstone

15. Facies association Facies Association 1 (FA1) Facies Association 2 (FA2 ) Facies Association 3 (FA3 ) Facies Association 4 (FA4 ) Facies Association 5 (FA5 ) Facies Association 6 (FA6 ) Facies Association 7 (FA7)

16. 16 Core-Log calibration Flood plain Channel bar Well HE 52 (C1) Well HE 28 (C1) Well HE28 (C2) Well HE 28 (C3)

17. Qz . = Quartz M. = Mica Kf . = K-feldspar H. = Heavy minerals M Kf Qz Cl Qz Kf Kf Kf Kf 1644.85 m Well HE 38 (C1 ) Well HE38 (C2) Well HE 38 (C3)

18. Bentiu One   Bentiu Two   Bentiu Three   Bentiu formation well correlation

19. Top Bentiu One NW SE Bentiu One staking pattern Bentiu One sand boy geometry Staking pattern and reservoir geometry

20. NW SE Top Bentiu Two Bentiu Two staking pattern Bentiu Two sand boy geometry

21. NW SE Top Bentiu Three Bentiu One staking pattern Bentiu One sand boy geometry

22. Element Symbol Principal lithofacies assemblage Geometry and relationships Channels CH Gm , St, Sc , Sh , Sr , Fl , Fm Basal fifth-order bounding surfaces. Erosively based with lag and irregular to planar upper surfaces. Crevasse splay CS Gm , Sc , Sr , Sh , Fm. Flat, sharp-based fine-grained sandstone, siltstone and claystone lobes and lenticular sheets Overbank fines OF Fl , Fm Surfaces usually planar or gently concavo-convex to sharp distinct bases. Top erosive irregular Architectural elements and conceptual model Floodplain deposits Braided channel deposits Over bank deposits Abandoned channel deposits

23. NW SE LST HST MFS SB       LST   HST       ------------- TS ------------   ________ SB ________   ------------- MFS --------- Bentiu One sequence stratigraphic framework

24.       TST   LST         ------------- MFS ---------   ------------- TS ------------   ________ SB ________     TS SB TST LST Bentiu Two sequence stratigraphic framework

25.       HST     ______ SB ______   ---------MFS-------- MFS HST HST Bentiu Three sequence stratigraphic framework

26.       HST   TST   LST   HST       ________ SB ­­________   -------------MFS---------   -------------TS------------   ________ SB ________   -------------MFS--------- LST LST LST TST TST TST HST HST HST HST HST HST Bentiu Formation generalized sequence stratigraphic framework

27. 27 Petrography of Bentiu formation Quartz (mono & poly) Feldspars Feldspar Perthetic texture Rock fragments Mica (Muscovite & Biotite ) Siderite cement Calcite cement Iron oxide chlorite Kaolinite Illite Smectite )

28. 28 Classification of sandstone of Bentiu formation Arkosic Quartz Arenite

29. 29 Bentiu One Petrophysical properties

30. 30 Bentiu Two Petrophysical properties

31. 31 Bentiu Three Petrophysical properties

32. Detailed core description and analysis reveal presence of nine lithofacies all are of fluvial origin. Those lithofacies were later grouped in seven facies associations based on their physical , chemical, biological and depositional environment. Core result was used to calibrate wireline log. The result of calibration reveal good agreement between core results and wireline log results. Extrapolation of the lithofacies to uncored succession using wire line logs and the calibration of wireline logs to the core confirm the core description and lithofacies results. Core results reveal that sandstone behave differently in some interval and produce high GR readings. CONCLUSION Thin sections result shows that the sandstone of Bentiu formation composed mainly of higher percentage of quartz and lesser feldspar little rock fragments and minor mica, heavy mineral and iron oxides, this matrix is mainly cemented with quartz, clay, carbonates and iron oxides.

33. 33 The sandstone model composition of Bentiu formation displayed by point counting analysis reveals the composition of this sandstone to be sub- arkose to sub- arenate in nature. Based on core description, well log interpretation, depositional environment and genetic relationship, architectural elements were interpreted and conceptual model was constructed. This result shows that Bentiu One was deposited in a braided stream environment, Bentiu Three in meandering stream environment and Bentiu Two in over bank environment . Based on well log results a system tracts were identified for Bentiu One, Bentiu Two and Bentiu Three. Those system tracts were combined together and a general sequence stratigraphic framework for Bentiu formation in the study interval of Heglig oil field was proposed. Those system tracts are HST, TST, LST and HST bonded by SB, MFS, TS, SB and MFS. Petrophysical studies indicate variations in the reservoir properties between Bentiu one, Bentiu two and Bentiu three, vertically and laterally, mainly controlled by facies and grain size changes. Bentiu one shows good reservoir quality compared to Bentiu two and Bentiu three. The reservoir quality of Bentiu two is a decrease due to high increase in shale ratio and water saturation. Bentiu three shows poor reservoir quality due to deep burial, which resulted in higher compaction and more cementation and still more decrease in grain sizes.

34. 34 RECOMMENDATIONs Core results show high GR reading in front of sandstone more data are required to interpret the reason why this happened. Sequence stratigraphic framework was constructed for Bentiu formation integrating bio-stratigraphic data into this framework will lead to a better understanding depositional environment and paleogeography of this formation.

35. 35 The study contributed to the rift basins in Sudan by providing new information related to the reservoir characteristics and heterogeneity. It enhances understanding the link between the petrophysical properties distribution within the reservoir and associated facies. As a result, more robust petro-facies models were generated originally in Muglad Basin for Bentiu One, Bentiu Two and Bentiu Three Formations. The study provides valuable details about the Cretaceous sections (first rift cycle) and filled the gap in knowledge in Muglad Basin in general and Heglig oil file in particular. It considered additional integrated study in Muglad Basin addressed the depositional facies and established petrophysical reservoir properties for Bentiu Formation (Late Cretaceous). The study adopted an unconventional approach that integrate data from different sources and scales for better insight and interpretation. This integration considered the main difference from previous work in Muglad Basin as data used independently ( Ex. Guan 2001 ). The study outcomes in terms of vertical and lateral facies distribution in 3D space and its relation to the petrophysical properties could be useful for the oil exploration and field development in Sudan. On the other hand, this practice and lessons learned is applicable to other similar rift basins in the region. Contribution

36. 36 The study introduced new precise facies classification in Bentiu formation of Heglig oil field in Muglad basin based on GR cutoffs. The facies classification used in this study is unique as a simple sand/shale facies classification was used in previous work. A sequence stratigraphic framework is proposed for Bentiu One, Bentiu Two and Bentiu Three, which was combine to form a generalized sequence stratigraphic framework for Bentiu formation in Heglig oil field in the Muglad basin. Sandstone in some core intervals read high GR in the wire line logs classified as shale, integration of core data, thin section and permeability readings from core with wireline log could reclassify those intervals as sandstones The study widened the horizons for new research directions in rift basins worldwide, particularly in Sudan. The adopted methods used in this study could be useful for future research.

37. Facies Integration of data Reservoir Properties facies classification in Bentiu formation valuable details about the Cretaceous sections unconventional approach that integrate data from different sources and scales A sequence stratigraphic framework is proposed for Bentiu One, Bentiu Two and Bentiu Three widened the horizons for new research directions in rift basins worldwide new information related to the reservoir characteristics and heterogeneity. Integration of core data, thin sections, and permeability reading with well logs, some sandstone showing high gamma ray previously classified as shale, could be reclassified as sandstone.

38. 38 Publications BOOK CHAPTER A. A. H. Taha , Abdul Hadi Abdul Rahman, Wan Ismail Wan Yusoff , 2015 . Application of wireline log in the determination of fluvial deposits of reservoir interval of Bentiu Formation ( Albian-Cenomanian ) Muglad Basin Sudan. Springer (P 365).   CONFERENCES   Ahmed Ali Hassan Taha , Abdul Hadi Abdul Rahman, Wan Ismail Wan Yusoff , 2014 . Application of wireline log in the determination of fluvial deposits of reservoir interval of Bentiu Formation ( Albian-Cenomanian ) Muglad Basin Sudan. International Conference on Integrated Petroleum Engineering and Geosciences (ICIPEG) Kuala Lumpur, Malaysia, (3-5 June 2014).   Ahmed Ali Hassan Taha , Abdul Hadi Abd Rahman, Wan Ismail Wan Yusoff , 2013 Lithofacies analysis of reservoir interval ( Albian – Cenomanian ) Bentiu Formation of SE Muglad Basin, Southeastern Sudan, International Oil and Gas Symposium and Exhibition (IOGSE) Sabah, Malaysia (09-11 October 2013).   Ahmed Ali Hassan Taha , Abdul Hadi Abdul Rahman, Wan Ismail Wan Yusoff , Mohamed Khalifa , 2012 . Facies and petrographic characteristics of Early Cretaceous (Late Albian-Cenomanian ) sandstone reservoir of SE Muglad Basin, Sudan. International Conference on Integrated Petroleum Engineering and Geosciences (ICIPEG) Kuala Lumpur, Malaysia, (12-14 June 2012).

39. Acknowledgement Friends and Colleagues Supervisors Family PRSB

40. ALHAMDULILAH &