The document discusses the geological characteristics and petroleum potential of the southern Indus basin, highlighting its formation due to tectonic activities related to the divergence of the Indo-Pakistan subcontinent from Gondwanaland. It details various geological structures, stratigraphy, and the success of exploration efforts leading to significant oil and gas discoveries in the lower Indus basin, including potential reservoirs and source rocks. The document also addresses the implications of seismicity on hydrocarbon generation and the overall geological evolution of the region.

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2. Lower Indus
Basin

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Dr. Naveed Ahsan
H. Jawad Sohail
Hammad Ahmad Sheikh

4. • 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.

6. • 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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9. 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.

10. • 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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11. • 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.

12. 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.

13. Stratigraphy of Southern
Indus basin

14. 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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15. 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.
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Fig: Generalized
Stratigraphic Column of the
Northern Kirthar Range.

17. 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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18. 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

22. 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

26. • 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.

27. • 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.

28. • 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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30. Source Rocks of Lower
Indus Basin
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31. 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.

32. • 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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34. • 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.

35. • 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

36. • 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 %.

37. 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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38. 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.

39. 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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