Learning s on basement fracturing and weathering in rift-shoulder fault blocks; a reservoir analogue from the Sinai Suez Rift (Egypt)

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$Learning s on basement fracturing and weathering in rift-shoulder fault blocks; a reservoir analogue from the Sinai Suez Rift (Egypt) Alvar Braathen, UNIS/UiO Mohamed M.$

1 Learning s on basement fracturing and weathering in rift-shoulder fault blocks; a reservoir analogue from the Sinai Suez Rift (Egypt) Alvar Braathen, UNIS/UiO Mohamed M. Abdel Fattah, Gouda Abdel-Gawad, Beni-Suef University, Egypt Snorre Olaussen, Kei Ogata, UNIS, Norway 1) Regional setting 2) Basement fields in the Suez Rift 3) Basement lithologies Main lithologies Diagenesis and weathering products 4) Datasets a) fracture systems in the basement b) tropical to arid weathering profile on top basement c) sedimentary deposits overlying basement 5) Summary and Conclusions Force workshop, Stavanger, 4 th April 2013

2 Ebbadalen Fm Before leaving the Norwegian shelf. BARENTS SHELF ANALOUGE Basement in exhumed fault blocks, Carboniferous Billefjorden Trough, Svalbard Basement offers a new HC play concept with significant learning potential? Billefjorden Gr. sandstone D U basement East side of the Billefjorden Trough c. 100 m basement old men, new knowledge Sverdrup Grieg Aasen

1) REGIONAL SETTING Suez Rift Mediterranean Abandoned arm of Red Sea Rift Oligocene-Miocene rifting 4-6 km structural relief 70 HC fields 8 fields producing basement Central rift (C) Rift terraces

3 1) REGIONAL SETTING Suez Rift Mediterranean Abandoned arm of Red Sea Rift Oligocene-Miocene rifting 4-6 km structural relief 70 HC fields 8 fields producing basement Central rift (C) Rift terraces (T) Rift shoulder (S) S African Plate T Gulf of Suez Facts on HC production from basement T S C T S T C Study area Sinai Peninsula C S S C Gulf of Aqaba Dead Sea Transform Arabian Plate Outstanding exposures Red Sea Satellite photo courtesy of NASA

4 Suez rift development Cambrian exhumation and weathering Miocene onset of maturation and migration Nubian sandstone Oligocene-Miocene burial forming top-seal K-Te pre-rift Miocene weathering Oligocene start of Suez rifting Oligocene exhumation Salah & Alsharhan 1998

5 Alsharhan & Salah 1997 Rift development geography and climate Ordovician Cambrian South 90 Batlas 2002 Cretaceous Miocene North 15 North 30 Exhumation during rifting Today Tropical to Desert weathering system Quartz Arenites; > 90% qtz, < 3% kaolinite 10-29% porosity md permeability Rodinia Deposits South Exhumation Ziegler et al. 1979

$effects variable intensity of fracture network internal segmentation of plumbing system$

6 2) BASEMENT FIELDS 70 fields 8 fields producing from basement Alsharhan & Salah 1997 Basement horst reservoir, with major sealing faults Well production varies: diagenetic effects variable intensity of fracture network internal segmentation of plumbing system Salah & Alsharhan 1998 HC column height = 340m top res. - GOC ~ 70m GOC - OWC ~ 270m Sinai study area

Basement fields well log though basement section, Geisum Field Certain pay zone 50m Certain Transition Top-basement weathering Deeper wells into basement encounter more

7 Basement fields well log though basement section, Geisum Field Certain pay zone 50m Certain Transition Top-basement weathering Deeper wells into basement encounter more good zones in the HC column Varied quality pay zone Good production 166m Mod.-Low production Salah & Alsharhan 1998 Fracture aperture= 0,01-1 mm Fracture Poro= 0,5-1,5%

Study area onland Sinai: Oblique view of top-basement contact of western Sinai rift, from center to shoulder Thal fault Rift Shoulder Study area Petrel

8 Study area onland Sinai: Oblique view of top-basement contact of western Sinai rift, from center to shoulder Thal fault Rift Shoulder Study area Petrel model based in Mostafa 2004 Coastal fault Baba fault Feiran fault Coastal fault Rift Center Model and graphics by Aleksandra Anna Smyrak-Sikora & Sebasitan Sikora

9 Location of study areas of Sinai Excellent exposures are found in the rift shoulder, where uplifted basement is partly exhumed Hamman-Farrun terrace Study areas Rift shoulder with smaller faults Barka plain with late-rift alluvium Rift-bounding fault Section studied Baba terrace

10 Oblique view into study area. Rift Shoulder Thal fault Baba fault Q alluvium

facies= 7-8 kbar / 6-700 C Granodiorite ~ 610 Ma Granite ~ 550 Ma Nubian

11 3) BASEMENT LITHOLOGIES 1. Granodiorite complex 2. Shear zone (schist) 3. Granite Pre-syn rift sedimentary cover Najd shear zone Biotite schist Amph.facies= 7-8 kbar / C Granodiorite ~ 610 Ma Granite ~ 550 Ma Nubian Sandstone cover Quaternary coastal plain Nubian Sandstone cover Pre-syn rift sedimentary cover

Granitoides (Granodiorite and Granite) => weathered

granodiorite, locally mingling with diorite Outcrop

grained granitoids Qtz+Kfsp+albite+hbl+bio+white mica

mafic minerals and fsp => Qtz+ kaolinite+ illite ±

montmorillonite ± hematite ± dolomite ± gypsum ±

12 Granitoides (Granodiorite and Granite) => weathered granitoides Intrusive complex of medium-coarse grained granodiorite, locally mingling with diorite Outcrop thin-section XRD Intrusive complexes of mediumcoarse grained granitoids Qtz+Kfsp+albite+hbl+bio+white mica Q M Weathering Kao pseudomorph of fsp Breakdown of mafic minerals and fsp => Qtz+ kaolinite+ illite ± albite ± microcline ± bio ± white mica ± montmorillonite ± hematite ± dolomite ± gypsum ± halite Sausuritization of fsp Medium grained red granite, locally fine grained or pegmatitic

13 Biotite schist => weathered schist Ductile shear zone cutting intrusive complex Fine-medium grained schist, showing transitions into lower strained granodiorite Qtz+bio+albite±Kfsp±hbl schist Weathering Breakdown of mafic minerals and fsp Qtz+bio+kaolinite+illite ± albite ± montmorillonite ± hematite ± gypsum ± halite

$Faults and fractures => weathering Thal fault, Throw ~$ = early cataclasites, superimposed breccias and gouge

$basement rocks => fractures mostly filled Granitoids =>$

14 Faults and fractures => weathering Thal fault, Throw ~ 2000 m FeO+kao+illite ± montm fracture fill Fault rocks = early cataclasites, superimposed breccias and gouge Qtz+ kaolinite+ illite+ fsp ± carbonate ± montmorillonite ± hematite ± halite Mafic-intermed. basement rocks => fractures mostly filled Granitoids => fractures mostly open

$a) fracture systems in the basement; a1) Fault damage zones$ $a2) background fracturing of shoulder Thal fault Border to$

15 4) DATASETS. a) fracture systems in the basement; a1) Fault damage zones a2) background fracturing of shoulder Thal fault Border to rift shoulder T > 2000m Fault core 15 m wide Fracture Intensity (f/m) per meter from fault Scanline across damage zone

$Fracture intensity per meter (f/m) Scanlines recording of fracture system, N= 39 Fracture orientations Salah & Alsharhan 1998 Rift shoulder with small faults fault Line# 18 Shoulder fault Large$

16 Fracture intensity per meter (f/m) Scanlines recording of fracture system, N= 39 Fracture orientations Salah & Alsharhan 1998 Rift shoulder with small faults fault Line# 18 Shoulder fault Large faults with FW damage zone Line# 23 Baba ft Background level, 1-5 f/m fault Line# 35 Shoulder Line# 4 Thal ft Background level, 1-4 f/m Backgroud level = 1-4 f/m Small fracture corridors = 3-10 m wide Inner damage zone = m wide Outer damage zone = m wide

$200m Sheet fractures Locally 50-100 m layer of sheet fractures Steep fractures Fracture$

17 4b) tropical to arid weathering profile (saprolite) along top of basement, and along faults T ~ 200m Sheet fractures Locally m layer of sheet fractures Steep fractures Fracture corridor

18 c. 20 m Weathering profile along top of basement Nubia Sandstones: Um Bogma Formation of dolomites and cemented marine sandstones Araba and Naqus formations of fluvial to marine sandstones Basement-cover contact A N UB Weathering profile Bio-hbl schist in basement

19 Measuring thickness of weathering profiles Araba Fm sandstones Geologist in paradise White weathering profile in red granite

20 Thickness of top-basement weathering profile (m) Top-basement weathering profile 9 sites (3 in schist, 6 in granite) 58 thickness recordings 40 Schist more variable, and proner to deeper weathering Schist, master fault Granite, master fault Granite fairly homogenous throughout Schist, shortest any fault Granite, shortest any fault Distance from fault / fracture corridor (m)

21 4c) Cambrian sandstones (Araba Formation) overlying basement. Coarser grained alluvial red beds passing upward to red to yellowish finer grained marine or lacustrine shoreline deposits basement

22 Sedimentary basement-cover transition Wadi Baba village Basal lag Mildly weathered biotite schist Basal sandstone lag Wadi Baba side valley Red granite

23 Cover sandstone facies Low angle cross stratification Wave ripples Hetereoliths Low angle planar cross stratification Weathered granite

24 Cambrian mixed fluvial and tidal/shoreline facies as cover deposits Cont. => shallow marine succession Continental succession Poro= 10-29% Perm= md

25 Sedimentary cover overlying basement upward increased maturity of the sandstones 4 m above basement granite Hetereolithic bed 50 cm above basement granite 10 cm above basement granite

26 Column hight? 5) SUMMARY AND CONCLUSIONS (Suez case) Note selective weathering and diagenesis of lithologies; Schist and mafic rocks with significant secondary mineralization Kaolinite (cement+clastic) and illite in weathering profile and partly in overlying sandstones HC RESERVOIRS Porous sandstone succession infilling basement relief Porous (10-20%) and permeable 5-15 m thick weathering profile on-top felsic intrusives Fractured basement reservoir with ~ 1-3% porosity PLUMBING SYSTEM Fault damage zones with open fractures in granitoids Selective deep weathering, and corroded fracture system along faults

27 Winner takes all - who will reach the basement first? Thank you AdventdalenSnakeWeasel Oil & Gas Field Inspection Abu Zenima, February 2012

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