Salt tectonics in the Thumrait area, in the southern part of the South Oman Salt Basin: Implications for mini-basin evolution

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1 GeoArabia, vol. 13, no. 4, 28, p Gulf PetroLink, Bahrain Salt tectonics in the Thumrait area, in the southern part of the South Oman Salt Basin: Implications for mini-basin evolution Badar Al-Barwani and Ken McClay ABSRACT The Upper Proterozoic - Lower Cambrian South Oman Salt Basin contains exploration targets consisting principally of slabs of carbonate encased within the infra-cambrian Ara Salt. The southern part of the South Oman Salt Basin was reviewed by using a 4 by 5 3-D seismic survey, 3 2-D regional seismic lines and 15 wells. The study focused on the evolution of the Ara Salt in relation to the overlying lower Paleozoic Nimr, Mahatta Humaid and Ghudun groups. Deformation of the thick sequence of Ara Salt dominated the history of mini-basins or Haima pods that developed above the salt. The syn-kinematic, predominantly clastic units of the Nimr and overlying Mahatta Humaid groups were deposited in the mini-basins above the Ara Salt. These sequences vary greatly in thickness due to salt movement. In seismic cross-sections, the Ara Salt is opaque, and obscured by seismic multiples generated by sub-horizontal reflectors higher in the section. Where internal geometries are imaged, however, complex internal structures are commonly observed. The Ara Salt structures evolved through several stages of deformation that were driven mainly by phases of sediment progradation from the west and northwest. Four main evolutionary phases for the mini-basins have been identified. Pre-existing topography and regional faults also played a role in triggering and delineating the regional salt trends. The basin has retained much the same shape from the Devonian Period until today. In contrast, in northern Oman, six salt domes have pierced the surface due to the reactivation of major basement faults during the late Palaeozoic. INTRODUCTION A large proportion of the world s discovered hydrocarbon reserves are associated with structures formed as a consequence of the movement of rock salt within the subsurface. In areas as diverse as the Gulf of Mexico, offshore Angola, offshore Brazil, Europe s North Sea and the Middle East, billions of barrels of oil and gas are trapped within salt-related structures. For example, 6% of the 6 billion barrels of oil reserves in the Middle East are related to salt structures (Edgell, 1996). The prevalence of salt structures and their implication for hydrocarbon prospecting has ensured that salt tectonics has been an active field of research for over 7 years. In Oman three infra-cambrian Ara Salt basins have been recognised: Fahud, Ghaba and the South Oman Salt Basin (Figure 1; Loosveld et al., 1996). Lees (1928) was among the first geologists to link the Ara Salt of Oman to the Hormuz Salt of the Arabian Gulf and Iran. Although many hydrocarbon fields have been discovered in the Oman salt basins (Al-Marjeby and Nash, 1986; Heward, 199; Loosveld et al., 1996), few studies have been published linking these to mini-basins developed by halokinesis above the salt. More recently, additional significant Proterozoic-Cambrian oil discoveries in the stringers incised in the Ara Salt of the South Oman Salt Basin have been made (Peters et al., 23; Amthor et al., 25; Al-Siyabi, 25). These discoveries, together with the growing exploration and continuing maturity of the salt basin provinces in Oman have increased interest in the stringers. A number of models have been proposed for the complex geometry of salt structures found within the region, ranging from down-building, differential loading, thin-skinned extension, compressional diaprism and salt dissolution (Heward, 199; Boserio et al., 1994; Loosveld et al., 1996; Al-Siyabi, 25). Nevertheless, it is clear that previous studies on salt tectonics in the South Oman Salt Basin have not fully explained the observed salt structures and their relationships to mini-basins above the salt in a regional context (Al-Barwani, 23). The principal aim of this paper is to develop an integrated model of salt tectonics in the South Oman Salt Basin. The paper uses 2-D and 3-D seismic data to show the 3-D geometries of the salt structures. It seeks to characterise their tectonic evolution while taking into account therights influence and effects of variable sedimentation patterns. IP: Copyright Gulf PetroLink 216. All Reserved. Downloaded by 3-D munirelmahdy87@gmail.com 77

2 Al-Barwani and McClay Arabian Gulf Makra n Fold Belt Gulf of Oman Ha wa UNITED ARAB EMIRATES Muscat a sin m O ns ai nt ou hee (Para-) autochthonous M st S an ru Th Hawasina Nappes S Ophiolite t Ordovician Amdeh Fm Saih Hatah Qalhat Basement Salt Basin Fahud Salt Basin East Oman Ophiolite Complex Batain Nappes 22 gh Huqf Outcrop em Hi r ka Fault uk Ma Jabal Ja alan 22 Maradi Fault Zone AlAshkharah o br Ma Strike-slip fault Syncline Masirah Trough Ghaba Salt Basin Anticline Hig qf Masirah Ophiolites Hu SAUDI ARABIA h Central Oman High OMAN Hi rn ste Fl k ctio n ati an efo rm Ea W Obl iq un d 18 South Oman Salt Basin ter nd gh hu on rb es Em ua yq t p Fr in as rte G Seismic line Figures 15 Waghald Basin 54 Caspian Sea TURKEY SYRIA Arabian Sea Med. Sea JORDAN N 3 IRAN IRAQ KUWAIT Thumrait area Figures 4 to 14 Qara Mountains 2 Arabian Sea ue O bdu on t Seismic line Figure 16 (Approximate location) Masirah Transform Fault Masirah Bay 2 BAHRAIN Al Halaniyat Islands Mirbat Cretaceous-Tertiary Salalah Basin QATAR N (Approximate) 56 EGYPT Arabian Shield 1 SUDAN Red Sea UAE OMAN SAUDI ARABIA YEMEN ERITREA Arabian Sea Figure 1: Regional tectonic map of Oman showing the major structural features and distribution of the salt basins (modified from Al-Siyabi, 25; Loosveld et al., 1996; Droste, 1997). Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

3 REGIONAL GEOLOGIC SETTING The South Oman Salt Basin is a NE-trending, asymmetric basin (Figure 1), approximately 4 by 15 in extent. It is bound to the west by a structurally complex zone, known as the Western Deformation Front, which was interpreted as a transpressional feature that became inactive in the Cambrian as manifested by the Angudan unconformity (Immerz et al., 2). It is bounded to the east by onlap and thinning of basin strata onto a structurally high crystalline basement. The basement of Oman and the Arabian Plate is believed to be a series of basement terranes that coalesced to form the western shield of the Arabian Plate during the Neopetrozoic (Husseini, 1989; Husseini and Husseini, 199; Stern, 1994; Al-Husseini, 2; Sharland et al., 21; Blasband et al., 21). The basin fill of the South Oman Salt Basin is comprised of up to 7 of sediments ranging in age from the Proterozoic to the Recent (Figure 2). The lower part comprises the Huqf Supergroup, which is divided into six lithostratigraphic units including the mobile Ara Group (Figure 2, Gorin et al., 1982; Sharland et al., 21). The hydrocarbon-bearing Ara carbonate stringers represent isolated carbonate platforms that consist of six third-order cycles of carbonates and evaporites (Peters et al., 23; Amthor et al., 25; Al-Siyabi, 25). The evaporites of the Ara Group are the key structural elements controlling the geometry of the overlying strata, and provide a mechanical detachment horizon between the mechanically brittle pre-ara and post-ara layers. Overlying the Ara Group, the clastics of the Lower Cambrian Nimr and Cambrian-Ordovician Mahatta Humaid groups were deposited in mini-basins associated with salt withdrawal. Devonian-Lower Carboniferous sediments of the Misfar Group (Figure 2) are sometimes preserved in dissolution lows on top of the salt ridges separating the mini-basins. At a regional scale, the Haima Supergroup is overlain by a thick, blanketing Carboniferous-Recent succession consisting of a mixture of clastic and carbonate platform deposits (Figure 2, Droste, 1997). The Oman sedimentary succession was affected by a series of Proterozoic to Recent regional tectonic phases. Five main tectonic phases have been identified (Stern, 1994; Loosveld et al., 1996; Droste, 1997; Johnson, 2; Sharland et al., 21): (1) A Proterozoic compressional phase (c. 715 to 61 Ma) of terrane accretion which led to the assembly of the Arabian Plate. (2) A Proterozoic to Carboniferous extensional phase (c. 61 to 325 Ma) during which the Huqf and Haima supergroups and Misfar Group were deposited in Oman. (3) A Mid-Carboniferous to Mid-Permian phase (from 325 to 255 Ma), laterally equivalent to the Hercynian Orogeny in Europe; the creation of the Neo-Tethyan Ocean and a new passive margin along the northeastern Arabian Plate margin. (4) A largely Mesozoic (Mid-Permian to mid-cretaceous) extensional phase (from 255 to 92 Ma). This phase was dominated by the deposition of carbonate and evaporites followed by mixed openmarine clastics and carbonates. (5) A late Mesozoic to Recent phase (from 92 Ma to present-day), which first commenced with the S Ophiolite obduction in the northeast and Masirah Ophiolite in the southeast, followed by the closure of the Neo-Tethys Ocean, uplift of the Oman Mountains and Zagros fold belt, and rifting and spreading of the Gulf of Aden and the Red Sea. SEISMIC STRATIGRAPHY Several key horizons were interpreted throughout the Thumrait area: base Ara Salt (top Nafun Group), top Ara Salt, several intra-ara Salt reflectors, top Mahwis, top Ghudun and top Natih-E. Figure 3 shows the seismic stratigraphy of the area using a representative seismic line segment. The seismic section is divided into four units based on salt-related deformation: (1) (2) (3) (4) Pre-kinematic section refers to the section below the Ara Salt; Mobile Ara Salt group; Syn-kinematic section includes the Nimr and Mahatta Humaid groups; Post-kinematic section includes the Ghudun, Haushi and younger groups, which blanket the entire basin All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP: Copyright Gulf PetroLink 79

4 Al-Barwani and McClay Age (Ma) Era Period Epoch NEOGENE TERTIARY PALAEOGENE 5 CENOZOIC Group North CRETACEOUS Major Hydrocarbon-Bearing Units FARS Fars Taqa AP11 AP1 Oligocene Eocene HADHRAMAUT Dammam Rus UER Simsima Shammar Fiqa Shargi AP9 AP8 Natih Nahr Umr WASIA 'Mesozoic Clastics' Shu'aiba Kharaib Lekhwair Salil Rayda Habshan KAHMAH Arab? Middle AP1 AP9 Fiqa Arada ARUMA JURASSIC MESOZOIC 15 South Pliocene Miocene Palaeocene 1 Chronostratigraphy SAHTAN Jubaila Kahmah Group (Shu aiba Formation) AP8 AP7 Hanifa Tuwaiq Dhruma Wasia Group (Natih Formation) Upper Mafraq AP7 AP6 Lower Mafraq TRIASSIC 2 Haushi AP5 AP4 Al Khlata Middle HABUR Misfar AP4 AP3 Middle MISFAR CAMBRIAN VENDIAN PRECAMBRIAN (SINIAN) 6 Haushi Group (Gharif, Al Khlata formations) Rahab HAUSHI Sahmah SAFIQ Middle MAHATTA HUMAID Saih Nihayda Barakat Al Bashair Ediacaran is hw Amin NIMR Veranger NAFUN Haima Supergroup (Mahatta Humaid Formation) Ghudun Barik Ma Angudan Unconformity AP3 AP2 Hasirah Miqrat Middle ARA 55 AP6 AP5 Lower Gharif Middle & Upper Gharif 5 Sudair Jilh Khuff HAIMA SUPERGROUP 45 AKHDAR Middle AP2 AP1 Haradh Karim HUQF SUPERGROUP 4 PALAEOZOIC 35 ORDOVICIAN SILURIAN 3 DEVONIAN CARBONIFEROUS PERMIAN 25 Minjur Ara Buah Huqf Supergroup (Ara Group) Shuram LEGEND Khufai Masirah Bay ABU MAHARA Ghadir Manqil Stuartian ~ 72 Ma? AP1 Conglomerate Dolomite Sandstone Anhydrite Siltstone Salt Shale Basement Volcanics Oil Limestone Gas 85 Figure 2: Chronostratigraphic chart of the South Oman Salt Basin showing the sedimentary and megasequences associated with the different tectonic events (modifiedip: from Copyrightrecord Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com Droste, 1997; Sharland et al., 21). 8

5 .5 The lower part of the seismic section features low-amplitude chaotic reflectors, representing the Nafun and Abu Mahara groups (below sec, not shown in Figure 3). Due to poor seismic resolution and poor lateral continuity, only one horizon was interpreted within this unit (base Ara Salt or top Nafun). SEISMIC HORIZONS The isochron of the Ara Salt across the study area varies from as little as 1 msec two-way time (TWT) (c. 2 m) in areas of complete salt withdrawal, to 5 msec TWT (c. 1,1 m) in areas of salt ridges. Within the Ara Salt, layers of high-amplitude, high frequency, discontinuous reflectors represent alternating layers of carbonates and evaporites. Natih E Postkinematic 1. Base Haushi The 6-msec-isochron interval (c. 1 ) between the top Ara Salt and the top Mahwis horizon represents the syn-kinematic sequence of the Nimr Group and lower part of the Haima Supergroup (Figure 3). The lowermost part of the Haima Supergroup is divided into the Amin and Mahwis formations, which were deposited in areas of salt withdrawal known as Haima pods or mini-basins. Onlapping surfaces, growth packages and unconformities have been interpreted in the fill of the Haima mini-basins. Correlation of horizons between pods is difficult due to significant changes in seismic character across each mini-basin and the occurrence of seismic multiples. These changes are caused by the nature of sedimentary deposits, which varies from mini-basin to mini-basin. The absence of well data also renders cross-basin correlations inconclusive. Top Mahwis Top Amin Intra-Amin Synkinematic Top Nimr 2. Top Ara Salt Internal reflectors: Stingers floating in salt Approximately 8 msec (c. 1.3 ) above the Mahwis Formation, the post-kinematic Ghudun Group has very poor internal seismic reflectivity, poor lateral continuity and consists of discontinuous reflectors. Only a few reflections can be confidently chosen and correlated over the entire survey. Unlike the underlying units, this sequence shows only minor variations in thicknesses. Over most of Oman, the prehaushi unconformity represents a gap of 1 million years (non-deposition and erosion) in the middle Palaeozoic (Droste, 1997). Mobile layer Base Ara Salt Buah, PreShuram and kinematic Khufai Figure 3: Seismic stratigraphy column of the Thumrait area showing the seismic character of the horizons interpreted and the relative ages. Between.6 and.3 sec TWT, the Permian to Cretaceous carbonate units are characterised by highamplitude, high frequency reflectors, with no significant variations in thickness. Extensional faults occur in this sequence above some salt highs. Above.3 sec TWT, low-amplitude, continuous reflectors are correlated with Tertiary and Recent deposits. Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

6 Al-Barwani and McClay SALT-RELATED DEFORMATION The geometry and evolution of the structures within the Thumrait area are described using five main seismic horizons: base Ara Salt, top Ara Salt, top Amin, top Mahwis and top Natih-E. Figure 4a shows a 3-D visualisation map of top Ara Salt in which thirteen salt-withdrawal mini-basins have been identified; these are chronologically numbered from west to east. Figure 4b shows the TWT isochron of the Ara Salt. Highs represent salt ridges and pillows, lows are salt withdrawal minibasins; both are clearly seen in the maps. Different Haima mini-basin morphologies are found in the Thumrait area. Haima mini-basins or pods are defined by isopach maxima, with lateral dimensions of 1 12, and are surrounded by salt ridges or pillows. These mini-basins are encircled with salt ridges, which are elongated and narrow (1 4 wide), with maximum depth-of-burial of up to c. 5 (3.2 sec) (Figure 4a and Table 1). The mini-basins vary in shape and size from 2 (e.g. part of XII) to approximately 12 in width (e.g. II). They are both circular and oval in shape, with the main mini-basin axis being oriented to the northeast or north. The term mini-basin refers to the creation of accommodation space controlled by salt withdrawal (Smith et al., 1993). These structures are commonly observed in salt basins worldwide, although their mode of formation may vary from one area to another. Examples of these structures are found in the Gulf of Mexico (Worrall and Snelson, 1989; Diegel et al., 1995; Rowan et al., 2), central North Sea (Hodgson et al., 1992; Smith et al., 1993; Stewart and Clark et al., 1999), and in the Red Sea (Heaton et al., 1995). Different styles of salt ridges have been observed in the study area (Figures 5 to 8). The Ara Salt ridges and pillows are typically spaced from 5 to 1 apart. Their classification is based on lateral dimension, depth-of-burial and type of halokinesis: Elongated salt ridges (Figures 4 to 8). These salt structures are long, with an irregular top surface. In some places they are completely surrounded by salt welds (i.e. no salt), whereas in other areas the salt has not been completely evacuated underneath the mini-basin. The maximum width of the salt ridge ranges from 1.. The depth-of-burial of these salt ridges also varies from approximately 2. (1.3 to 1.7 sec TWT). Ten elongated salt ridges have been found in the area. They are usually inter-connected (Figure 4), asymmetric and associated with growth faults that sole-out on top of the Ara Salt (Figures 5 to 8). Table 1 Orientation of the Main Axis Size I N-S 3x6 II E-W Mini-basin () Maximum Mini-basin Height Maximum Time (Msec TWT) Weld 1,13 3,12 Yes 1,25 3,12 (Msec TWT) Notes III Circular 15 x 14 1,8 2,86 IV N-S 6x3 71 2,89 V NE-SW 7x4 6 2,8 7x4 7 3, Partially covered 8x6 1,9 2,89 Partially covered VI E-W VII Circular VIII E-W IX N-S 3x3 1,3 2,76 X NE-SW 1 x 7 1,5 2,55 XI NE-SW 13 x 6 7 2,32 XII E-W 11 x ,21 XIII Circular 13 x 1 1 1,84 Yes Yes Partially covered 3 small mini-basins No Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

7 Elongated salt pillows (Figures 5, 7 and 8). Three examples of this type of salt wall were found in the study area. They differ from the elongated salt ridges in terms of size, shape and depthof-burial. They are NE-oriented, pyramidal, with a maximum thickness of c. 1,1 m (5 msec TWT) and an average width of at the centre of the pillow. The burial depth of both these structures is approximately 3.7 ( sec TWT). Salt walls (Figure 6). Two salt walls (c. 7 thick) were formed within the 3-D seismic survey. One is located at the southeast end of the survey area and the other was found in the central southern section. They have a minimum depth-of-burial of c. 2,25 m ( sec TWT). Salt-dissolution features (Figure 8). Three salt dissolution features were formed on top of some salt ridges. They are small (2 wide) circular features separated by small salt ridges. From the analysis of the TWT thickness map of the Ara Salt (Figure 4b), a series of salt welds were formed and there was complete or near complete salt evacuation from underneath some of the minibasins (i.e. mini-basins II, III, VIII, X, and XI). DETAILED ANALYSIS OF MINI-BASIN FORMATION A number of significant observations that provide clues to the evolution and nature of the salt minibasins have been made from the analysis and interpretations of various seismic cross-sections. In general, the sedimentary fills in the mini-basins exhibit the following features (Figures 5 to 9): (a) (b) (c) (d) (e) (f) onlap of tilted/folded reflector packages; top-lap of tilted reflector packages; divergent packages of reflectors; folding of Haima units over salt ridges; fault terminations of intra-nimr and intra-haima reflectors on salt ridges; erosional truncation at the top Mahwis unconformity. The mini-basins in the Thumrait area have a sub-circular shape with a dominant northeast orientation. Their sedimentary fill is complex, and because of considerable thickness variations and the lack of impedance contrast, cross-correlating seismic data from one mini-basin to the next across salt ridges is difficult. Only the identification of major units is possible. Local unconformities, relevant only to one single mini-basin, can be occasionally observed on seismic data. It is most likely that most of these mini-basins had distinct infill histories controlled by salt withdrawal, erosion and volume of sediment deposited. Classification of Mini-basins The mini-basins found in the study area are subdivided into four main groups (Figure 4b). This classification is descriptive because there are no correlations possible between the mini-basins to tie certain markers in the Haima. The subdivisions are based on time of growth, size and seismic characteristics. First-Generation Mini-basins The first-generation mini-basins formed at the early stages of halokinesis as a result of the deposition by the Nimr Group, which is the youngest group of the Huqf Supergroup (Figures 4b and 1). Six mini-basins have been identified. These are NE-oriented and located to the west of the survey area. They are asymmetric, encircled with salt ridges and associated with complete salt evacuation. Some of the salt ridges associated with these mini-basins are controlled by pre-existing faults. Second-Generation Mini-basins The second-generation mini-basins formed as a result of the second phase of sediment deposition by either the upper part of the Nimr Group or the Amin Formation (Figures 4b and 11). This group is comprised of six mini-basins, which are located adjacent (mainly to the east) to the first-generation mini-basins. Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

8 VI I 54 2 V II IV VII III 54 3 a VIII XII b IX XIII c X 54 4 XI N Figure 4a: Seismic structural map (two-way time) of top Ara Salt in Thumrait area, South Oman Salt Basin (see Figures 1 and 2 for location). 1. THUMRAIT AREA TIME MAP WITH MINI-BASINS I XIII 5 Al-Barwani and McClay Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

9 ' 1st 2nd 2nd 54 2' 2nd 4th 1st Generation 4th 3rd 1st 54 25' 2nd Generation 4th 54 3' 4th 3rd 4th 1st 54 35' 2nd 2nd 1st 54 4' 5 3rd 4th 2nd Generation N Figure 4b: Seismic isochron map (two-way time) showing orientation of basins relative to surroundings salt ridges. White and yellow coloured areas indicate complete to near-complete salt withdrawal and are referred to as "welds". Mini-basin types are: (1) first generation; (2) second generation; (3) third generation; and (4) fourth generation, associated with salt dissolution (see Figures 1 and 2 for location) ' 18 3' ' THUMRAIT AREA ISOCHRON MAP WITH FOUR MINI-BASIN GENERATIONS Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

10 Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by IP: East 4. Figure 5a: E-W seismic Line B, Thumrait 3-D survey (see insert for location of line B, and Figures 1 and 2 for location of Thumrait 3-D survey). SEISMIC LINE B, THUMRAIT AREA 3. West Al-Barwani and McClay

11 Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by IP: Salt ridge Ba Natih E Salt pillow Mini-basin III PRE-SALT SEQUENCE Salt weld MAHWIS PERMIAN TO RECENT Chaotic reflectors NIMR AMIN Mini-basin II Salt ridge ARA SALT? Mini-basin XIII alt Ara S Base Figure 5b: Interpretation of seismic Line B showing the geometries of salt-related withdrawal mini-basin II, III and XIII. Stringers? nformity se Haushi Unco West SEISMIC LINE B, THUMRAIT AREA? 5 East

12 88 Figure 6a: E-W seismic Line C, Thumrait 3-D survey (see insert for location of line B, and Figures 1 and 2 for location of Thumrait 3-D survey) East SEISMIC LINE C, THUMRAIT AREA West Al-Barwani and McClay Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

13 89 ARA SALT Salt ridge MAHWIS NIMR UPPER AMIN Mini-basin V PRE-SALT SEQUENCE Salt ridge LOWER AMIN GHUDUN Mini-basin IV NIMR Stringers? MAHWIS ARA SALT Massive salt ridge East Figure 6b: Interpretation of seismic Line C showing the geometries of salt-related withdrawal mini-basin. Mini-basin IV is an example of a third-generation mini-basin caused as a result of salt withdrawal from the flank of the salt ridge West SEISMIC LINE C, THUMRAIT AREA Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

14 9 Figure 7a: NE-SW seismic traverse A, Thumrait 3-D survey (see insert for location of line A, and Figures 1 and 2 for location of Thumrait 3-D survey) Southeast SEISMIC LINE A, THUMRAIT AREA Northwest Al-Barwani and McClay Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP:

15 MAHWIS Northwest NIMR AMIN PRE-SALT SEQUENCE Salt ridge SEISMIC LINE A, THUMRAIT AREA NIMR CRETACEOUS Mini-basin X Stringers Salt pillow Figure 7b: Interpretation of seismic Line A showing the geometries of salt-related withdrawal mini-basins. ARA SALT Possible Carbonate Stringers Salt ridge GHUDUN Mini-basin VIII ARA SALT MAHWIS AMIN Southeast Mini-basin XI Copyright Gulf PetroLink 216. All Rights Reserved. Downloaded by munirelmahdy87@gmail.com IP: