Petroleum Systems Elements and Structural Geology in Northern Iraq

Transcription

1 Petroleum Systems Elements and Structural Geology in Northern Iraq Graham Banks, PhD University of Calgary seminar, January 20, 2012 x3 vertical exaggeration

2 2 ACKNOWLEDGEMENTS I thank WZ management and colleagues for support and permission to present this work This work was a team effort Success is due to the wisdom, enthusiasm and professionalism of our team of WZ geologists, security and logistics staff, and the people of Kurdistan

3 3 AIMS AND CONTENTS Principal aims To give an overview of hydrocarbon exploration in Kurdistan Demonstrate a few tools used in Kurdistan for New Ventures studies Update published definitions of Zagros-Taurus structural domains Location and regional tectonics Summary of current hydrocarbon exploration Summary of petroleum systems Tectonostratigraphic evolution Main challenges to exploration Review of structural domains of the orogenic belt Conclusions

4 4 LOCATION AND REGIONAL TECTONICS Kurdistan region of northern Iraq Present-day collision and rotation of Arabian Plate, thus regional dextral transpression AGU blogosphere, 2010

5 5 CURRENT HYDROCARBON EXPLORATION Favourable Production- Sharing Contracts to the exploration companies 40 operating companies, including NOCs

6 6 CURRENT HYDROCARBON EXPLORATION Resource estimate: 40 BBO and 60 TCF of gas (USGS, 2000) Under explored: >100 undrilled anticlines High discovery:well rate Stable and safe compared to rest of Iraq Region has potential to be a significant global energy player Kirkuk Field. 25BBL recoverable and proven. Production since 1927 (Verma et al., 2004)

7 7 PETROLEUM SYSTEMS OVERVIEW All elements in place and low risk 2 major, producing plays: Tertiary Main Limestone Group and Upper-Mid Cretaceous Group Multiple source rocks (Paleocene, Cretaceous, Jurassic, Triassic) Multiple reservoirs (Miocene to Triassic). Mainly fractured carbonates Excellent evaporite and shale top seals >100 large, undrilled anticlines Favourable timing of trap formation v hydrocarbon generation-migration Contractional tectonics from Late Cretaceous Main deformation Miocene today (Zagros and Taurus fold and thrust belts) Current hydrocarbon generation and abundant hydrocarbon seeps

8 TECTONOSTRATIGRAPHIC EVOLUTION WNW 4. Pliocene present-day dextral transpression - Trap and seal creation - Hydrocarbons generated 3. Late Cretaceous Late Tertiary convergence of Arabian and Eurasian Plates - Early traps formed? - Reservoirs and seals deposited - Type II source rocks deposited, hydrocarbons generated NW Jurassic Mid Cretaceous passive margin in sub-equatorial setting - Type II source rocks deposited, hydrocarbons generated - Reservoirs deposited Legend Clastics Evaporites Carbonates Shales 8 Source rock 1. Permian Early Jurassic rifting of N. Gondwana NW Modified after PGA,

9 9 MAIN CHALLENGES TO EXPLORATION Data and expertise Much lost during decades of political instability Large distances between wells Published naming conventions do not reflect geological processes and/or are misleading Exploration and Operations Large traps buried by Pliocene not seen on satellite imagery Active deformation Wellbore instability and overpressured zones

10 10 NEW VENTURE EXPLORATION TOOLS Advanced processing and study of satellite imagery is key for: a. Discerning outcrop lithologies 10km magenta = fractured clays/carbonates reservoir at surface green / blue = iron oxides Springs N Red = healthy vegetation b. Mapping and analysing major structures Banks and Watkins, 2008

11 NEW VENTURE EXPLORATION TOOLS c. Identifying subtle/deep faulting that may have affected reservoir units: (a)? - The structural trend appears to be WNW-ESE - Minor NE-SW strike slip - No major lineament (a) visible Major NE-SW lineaments show syn- / post-mid Miocene reactivation En echelon folds (#) above the Sinjar-Herki fault ("active pre- Late Cretaceous", Jassim and Goff, 2006). 11 # # Mid - Lower Miocene formations # 10 km 380m a.s.l # # (a) 290m a.s.l Banks and Watkins, 2008 Banks and Watkins, 2008

12 12 SCHEMATIC SURFACE GEOLOGY MAP Igneous & metamorphic Thick Neogene sequence covers folds and is now actively deforming Late Cretaceous ophiolite Abrupt change from Neogene- to Mesozoic-aged rocks at surface across the mountain front Structural domains are generally parallel the orogenic belts, with promontories and embayments

13 13 PUBLISHED STRUCTURAL DOMAINS Modified after FRL (2010) 4 Zagros-Taurus domains defined in literature Names misleading The Zagros Suture Zones (2006) An unnamed part of The Thrust Zone (2010) Stable Shelf The Foothills Zone (2006) The Zagros Foredeep (1995) The Low Fold Zone (1987, 2010) The Thrust Zone (1987, 2010) The Imbricated Zones (2006) The Simple Fold Belt (1995) The Simply Folded Zone (2008) The High Folded Zone (1987, 2010)

14 14 PUBLISHED STRUCTURAL DOMAINS Modified after FRL (2010) There appear to be 5 not 4 Zagros-Taurus structural domains Bekhme Sara Miran Azmar Require more appropriate names that objectively describe the visible deformation at surface and on public domain data Kurdamir- Garmian

15 15 THE FOOTHILLS / LOW FOLD ZONE Modified after FRL (2010) Kurdamir- Garmian

16 16 THE FOOTHILLS / LOW FOLD ZONE ~500m amsl with current tilting and uplift The Foothills/Low Fold Zone Thick Pliocene molasse of conglomerates, sandstones and siltstones Qulijan Sarhad village Photos of topography Looking WSW

17 17 THE FOOTHILLS / LOW FOLD ZONE Shakal Thrust from 30,000ft. Looking ~SE Mid-Miocene upon Pliocene 10s metres surface topography though 10 to >50 kms long Photo of Shakal thrust

18 THE FOOTHILLS / LOW FOLD ZONE SW A Composite cross-section through Kurdamir-Garmian blocks Sarqala 1 A B Kurdamir-1 Gentle open folds above Miocene detachment TD 4077 m TD 4357 m Horizon Legend Lower Bakhtiari Upper Fars Decoupling across several major detachment zones Lower Fars Evaporite Base Fars Detachment Lower Fars Transition Beds Jeribe Aaliji/Shiranish Gulneri/Qamchuqa Numerous anticline targets not predictable from surface structural geology 18 Chia Gara Modified after WZ Corporate Presentation 2008 NE B

19 THE FOOTHILLS / LOW FOLD ZONE Looking NW Aj Dagh Mountain: not a low fold Drozna Village Drozna strike slip 19 N-S dextral strike-slip fault (as predicted from regional strain ellipse) 3 major joint sets provide good network connectivity for fluid flow in subsurface reservoir beds

20 20 NAMING STRUCTURAL DOMAINS Modified after FRL (2010) This currently deforming foreland basin be named Foothills Fold and Thrust Zone Foothills Fold and Thrust Zone Is the preferred domain to explore for hydrocarbons in: - In front of the main mountain ranges - Well-sealed Tertiary and Cretaceous reservoirs - Current oil generation into large anticlines - Close to infrastructure - Multi-prospect acreages

21 21 THE MOUNTAIN FRONT FAULT Modified after FRL (2010) Moving NE, this is the first major mountain range encountered Bekhme Misleading name: not a major fault at surface for the vast majority of its length It strikes from Syria to SE Iran 9 exploration blocks along it in Iraq Several are currently being drilled

22 THE MOUNTAIN FRONT FAULT Part of Qara Dagh license block from 20,000ft. Looking ~SE Decapitated box fold: after carbonate carapace hinges breached Qara Dagh from the air Tectonic elevation of hinterland 2.5km 600m high 22 Next page view

23 THE MOUNTAIN FRONT FAULT Overturned backlimb of Qara Dagh Anticline, looking S into partly eroded core 23 Most of the MFFZ I ve seen has no major fault at surface

24 24 THE MOUNTAIN FRONT FAULT Looking ~N Forelimb of Bazian Anticline: a tall fold Here a segment of a regional monocline: Alpine geowarping (Ameen 1991) Looking ~NE 450m high

25 25 A GOAL OF EXPLORATION Bekhme Gorge Looking ~east Oil in a pre-folding fault (bedding is ~vertical) Huge fault porosity! Must unravel progressive deformation

26 26 THE MOUNTAIN FRONT FOLD ZONE A distinct structural domain: anticline chain, in places a monocline An accurate name would be Mountain Front Fold Zone A challenging structural domain for drilling: - Thickened seals - Hinge lines decoupled between surface and reservoir level anticlines - Tough seismic acquisition and imaging - Often karstified reservoir carbonates at surface

27 27 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Modified after FRL (2010) In the Zagros-Taurus Mountain belt proper Some of the license blocks only recently awarded Sara Miran Seismic acquisition and wildcat drilling stage Azmar

28 28 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE SW Heritage Oil seismic dip line NE Heritage Oil corporate presentation, 2008 Reverse-reactivated normal faults Major detachments, probably Triassic evaporites and mudstones Folding dominates over thrusting, suggesting multiple decollements

29 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Mountain Front Monocline dipping to the SW: into the wall * Castle of the blind king Apparent sheath fold in Tanjero Fm Hinge line folded into SW transport direction * Modified after 150/Lectures/ShearZones/15shearZns.htm 29 Not simple folding!

30 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Anticlines are tall, asymmetric and have steep to overturned limbs Looking East Axis? Sara Anticline ~1000m high 30 Region s conventional Cretaceous reservoirs exposed at surface: this is the prolific Qamchuqa Fm type section

31 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Anticlines are tall, asymmetric and have steep to overturned limbs Looking East Sara Anticline ~1000m high Axis? 31 Region s conventional Cretaceous reservoirs exposed at surface: this is the prolific Qamchuqa Fm type section

32 32 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Shiranish Formation Seeps from exposed reservoir units, e.g. along NNE-SSW strike-slip fault Oil lubricating faults? Oil on all fracture sets here

33 33 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Kometan Formation Seeps in exposed reservoir units, e.g. along NW-SE strike-slip faults Picture of big strike-slip roadcut

34 34 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Shiranish Formation Note width of fault zone and potential for fluids to pass through shaly units Looking ENE Carbonate unit Marly unit

35 35 THE SIZE OF THE PRIZE Rowanduz Gorge and the Hamilton road The core of a box fold Scaling up the bitumen cascade outcrop to the trap scale Barrels of oil capacity of just this formation in a sealed anticline?

36 36 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Pir-i-Mugurun Gorge Looking NW Folding of the competent limestones-dolostones of the Qamchuqa Formation

37 37 THE SIMPLE / SIMPLY / HIGH FOLDED ZONE Complex, tight deformation in Lower Cretaceous in fold cores Reservoir potential in highly fractured, calcareous units Core of Azmar Anticline Looking E

38 38 THE HIGH AMPLITUDE FOLDED ZONE Transversal terranes and their boundaries must be understood too: a presentation in itself The name High Amplitude Fold Zone is suggested Few thrusts. Normal and strike-slip faults mostly: pre-neogene extension and present day transpression? A challenging domain for hydrocarbon exploration: - Huge folds - Region s main reservoirs at surface - Deep gas targets?

39 39 STRUCTURAL DOMAIN CONCLUSIONS 5 structural domains Suggested new names that accurately describe the deformation styles This assists New Ventures assessment of hydrocarbon prospectivity in the Iraqi Zagros-Taurus Mountain Front Fold Zone

40 40 KURDISTAN REGIONAL CONCLUSIONS Much potential for undiscovered hydrocarbons - Lower risk in the Foothills Fold and Thrust Zone - More challenging and higher risk nearer the orogenic core Kurdistan deformation is not as simple as current NW-SE folding and SW-directed contraction Complex deformation and fluid flow observed in all formations, including of Upper Pliocene age Normal, strike-slip and reverse faults are common, striking N-S, E-W, NW-SE. More normal and strike-slip faulting has been seen at surface than thrusting Folding dominates thrusting and is complex, e.g. monoclines, recumbent, sheath. Needs to be understood for each formation

41 41 ZOOR SWPAS