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Lower Indus Basin

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Presented To:Dr. Naveed Ahsan

Presented by:

H. Jawad SohailHammad Ahmad Sheikh

• The southern Indus basin is identified as an extension basin resulting from an inferred fossil-rift crustal feature overlain by a thick sedimentary sequence. Extension was a consequence of temporal divergence of the Indo-Pakistan subcontinent from Gondwanaland during the early Paleozoic.

• Based on magnetic-anomaly trends, the Indus basin fossil-rift feature is characterized by horst and graben structures, together with a system of transcurrent faults.

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The Jacobabad, Mari-Kandhkot and Lakhra highs all have the appearance of horst blocks and probably formed in response to the extensional tectonic style of Lower Indus Basin (Quad Report, 1994) which formed in response to the spreading axis between Madagascar and the Indo-Pakistan continental mass in the mid Cretaceous. Later transpression between the convergent Indo-Pakistan and Eurasian plates caused inversion and the superimposition of a transform style.

• The association of seismicity events and basement crustal features suggests that Tertiary reactivation of individual segments of the inferred rift structure has deformed overlying sequences of the Indus basin and also the surrounding areas, particularly the fold and thrust belt of Pakistan on the western side of the basin.

• The proposed geological models also illustrate the potential for appropriate environments for development of hydrocarbon source rocks, sufficient heat for thermal maturity, and structures for reservoirs and seals, suggesting more bright prospects in the southern Indus basin.

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GEOLOGICAL FRAMEWORK

The Lower Indus Platform Basin is bounded to the north by the Central Indus Basin, to the northwest by the Sulaiman Fold belt Basin and the Kirthar Fold Belt Basin in the west. The main tectonic events which have controlled the structures and sedimentology of the Lower Indus Basin are rifting of the Indian Plate from Gondwanaland (Jurassic or Early Cretaceous) which probably caused uplift and eastwards tilting at the start of the Cretaceous.

• Separation of the Madagascan and Indian plates in the Mid to Late Cretaceous which may have caused some sinistral strike-slip faulting in the region, hotspot activity and thermal doming at the Cretaceous-Tertiary boundary.

• This in turn caused uplift, erosion, extrusion of the Deccan flood basalts and probably the NNW-striking normal faults.

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• Paleocene-Eocene emplacement of the Bela

ophiolites may have caused gentle folding, Eocene passive margin conditions caused structural quiescence and carbonate deposition, Oligocene to present-day.

• Himalayan collision caused sinistral transpression in the west of the Lower Indus Basin, with fold-thrust structures overprinted by sinistral flower structures.

This tectonic province is underlain by infra-Cambrian to Recent clastics and carbonates. It remained passive margin until the Late Cretaceous, then became part of the complex suture between the Indian Plate and the Afghan Block. The stratigraphic succession changes from east to west. Precambrian basement is exposed in the southeastern corner of the basin. The thickness of the sediments increases westward. Important unconformities occur at base Permian and base Tertiary. In the eastern part of the basin, Tertiary has direct contact with the Jurassic sequence.

Stratigraphy of Southern Indus basin

Lower Indus Basin

• The basin is subdivided further into three parts :

Kirthar Fold Belt Lower Indus Platform Kirthar foredeep

• Indus offshore

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Kirthar Fold Belt• It is north-south trending tectonic feature quite

similar to Sulaiman fold belt in structural style and stratigraphic equivalence.

• Petroleum system(s) are well established in the area.• Cretaceous and Paleocene clastics(Mughal Kot, Pab

and Ranikot), and Eocene carbonates(SML and its equivalent) are the reservoirs.

• Nevertheless Pab holds some of the big gas discoveries of the area.

• The area has several discoveries of small and large size such as Jhal Magsi, Mazarani, Mehar, Bhit, Zamzama, Badhara, Kothar, Sari and Hundi etc.05/01/2023

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Fig: Generalized Stratigraphic Column of the Northern Kirthar Range.

Lower Indus Platform• The Lower Indus Platform(including Kirthar

foredeep) is also the highest explored area of Indus Basin. The platform is also known as “Badin Block”.

• Play type is tilted fault blocks developed in response to extensional tectonics.

• Primary reservoir is the Upper Cretaceous Goru clastics, which is sourced by organic rich shales of Sembar and Goru.

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Offshore Indus Basin• The Indus Offshore exhibit two play types i.e. Miocene

& Pliocene deltaic sequence having source, reservoir and seal and Eocene / Oligocene carbonate buildup/ platform remnant with Paleocene shales below (source) and Eocene-Oligocene shales above(seal).

• The basin has very limited exploration history.• Merely 15 wells have been drilled in the last 50 years of

exploration.• Pakcan-1 is the only sub-commercial gas producing well

in this area.

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Petroleum System

Lower Indus Basin• Basin-wise success rate has been the highest for

lower Indus Basin(due to strings of discoveries in quick succession in relatively small tilted fault blocks in Lower Goru reservoir).

• During 1980s, several oil/gas /condensate discoveries in the Lower Goru Formation were made. Exploration efforts geared up further in 1990s when some significant gas discoveries were made in the Late Cretaceous clastics (e.g. Bhit & Zamzama discoveries).

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Figures showing many Oil/Gas Field Discoveries in Lower Indus Basin

Reservoir Rocks of Lower Indus Basin

• Potential reservoirs in the Eocene include Limestone of the Habib Rahi and Pirkoh members of the Kirthar Formation.

• Ranikot sandstone is the main reservoir in the Dhodak oil and gas field.

• The Pab sandstone along with sand horizons within the Mughal Kot Formation is the most potential reservoir in the area.

• Sember and Lower Goru sandstone of Cretaceous age and Chiltan limestone of Jurassic age have tested commercial quantities of hydrocarbons at Rodho gas field of Dewan Petroleum.

• The principal reservoirs are deltaic and shallow-marine sandstones in the lower part of the Goru in the Lower Indus Basin and the Lumshiwal Formation in the Middle Indus Basin and limestones in the Eocene Ghazij and equivalent stratigraphic units.

• Potential reservoirs are as thick as 400 m. Sandstone porosities are as high as 30 percent, but more commonly range from about 12 to 16 percent; and limestone porosities range from 9 to 16 percent. The permeability of these reservoirs ranges from 1 to > 2,000 milidarcies (md).

• The largest reserves were found in the 625 m thick Eocene Sui Formation Sui Main Limestone Member. The Sui Upper Limestone Member and upper Eocene Habib Rahi Limestone were also productive.

• In 1999, Upper Cretaceous Pab Sandstone Formation gas production began at Sui field.

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Source Rocks of Lower Indus Basin

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Source Rocks of Lower Indus Basin

• Sembar has been identified as the primary source rock for much of the Greater Indus Basin, there are other known and potential source rocks.

• Rock units containing known or potential source rocks include the Salt Range Formation "Eocambrian" shales, Permian Dandot and Tredian Formations, Triassic Wulgai Formation, Jurassic Datta Formation, Paleocene Patala Formation, Eocene Ghazij Formation, and lower Miocene shales.

• In the offshore areas of the Indus geologic province, Miocene rocks are postulated to be good hydrocarbon sources, with the Sembar contributing in the shelf area.

• In the Lower Indus Basin and the Sulaiman-Kirthar geologic province, fluvial sandstones and estuarine shales and limestones make up the Paleocene Ranikot Group.

• sandstones of the Ghazij Formation are conformably overlain by interbedded limestones and shales of the Eocene Kirthar Formation.

Source Rocks of Lower Indus Basin

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• Nearshore sandstones and shales of the Oligocene Nari Formation and shales of the lower Miocene Gaj Formation make up the Momani Group.

• The Lower Cretaceous Sembar Formation consists mainly of shale with subordinate amounts of siltstone and sandstone.

• The Sembar was deposited over most of the Greater Indus Basin in marine environments and ranges in thickness from 0 to more than 260 m.

• Rock-eval pyrolysis analyses of 10 samples from the Jandran-1 well in the Sulaiman Range of the fold belt, indicate an average total organic carbon content (TOC) of 1.10 percent.

• The TOC values from the Sembar in two Badin area wells in the foreland portion of the Lower Indus Basin have TOC’s ranging from 0.5 to 3.5 percent and averaging about 1.4 percent.

• Across-plot of pyrolysis data indicates that the organic matter in the Sembar is mainly type-III kerogen, capable of generating gas.

• With respect to the oil window (0.6 - 1.3 percent vitrinite reflectance), the Sembar ranges from thermally immature to over mature. The Sembar is more thermally mature in the western, more deeply buried part of the shelf and becomes shallower and less mature toward the eastern edge of the Indus Basin

• Geochemical analysis of samples from Habib Rahi Limestone in northern Sulaiman Range show its maturity level oil.

• The limestone of Pirkoh member of Kirthar Formation contain TOC in the range of 0.4 – 3.5 %.

Seal

• The known seals in the system are composed of shales that are interbedded with and overlying the reservoirs, especially intra-formational shale for Lower Cretaceous reservoirs.

• In producing fields, thin shale beds of variable thickness are effective seals. Additional seals that may be effective include impermeable seals above truncation traps, faults, and updip facies changes.

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Traps

• The tilted fault traps in the Lower Indus Basin are a product of extension related to rifting and the formation of horst and graben structures.

• The temporal relationships among trap formation and hydrocarbon generation, expulsion, migration, and entrapment are variable throughout the Greater Indus Basin.

• In the foreland portion, formation of structural traps pre-date hydrocarbon generation, especially in the Lower Indus Basin.

References• A speculative tectonic history of Pakistan and surroundings;

some constraints from the Indian Ocean, in Farah, Abdul, and Dejohn, K.A., eds., Geodynamics of Pakistan: Geological Survey of Pakistan, p. 5-24.

• Farrukh Daud, Gulzeb Nabi Khan, Muhammad Ibrahim (2011), “Remaining hydrocarbon potential in Pakistan as statistical review”, PAPG/SPE ANNUAL TECHNICALCONFERENCE 2011 November 22-23, 2011, Islamabad.

• Athar Jamil, Dr.Abdul Waheed & Dr. Riaz A Sheikh (2009), “Pakistan's Major Petroleum Plays - An overview of Dwindling Reserves”, SPE/PAPG ANNUAL TECHNICAL CONFERENCE 2009

• November 17-18, 2009, Islamabad.

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Any QuestionI am listening!!!