Explorationstrategy 1 indus basin (platform)

Explorationstrategy
In Pakistan, the early exploration approach of merely searching for favourable locations within sedimentary basins has been replaced in recent years by a comprehensive and scientific basin analysis aimed at understanding why, when and how petroleum occurs in a basin. Raza et al (1989) introduced sedimentary basins and delineate 24 possible petroleum zones within seven main tectonic  features of these basins(Fig.22).

Indus Basin: 

According to Raza et al. (1989), the Indus Basin has an area of 533, 540 km² with an
average of 4.8 km thick sedimentary section. The sedimentary rocks in the basin range in age from
Late Precambrian to Recent and are predominantly of marine origin. A large number of oil and gas
seepages/shows occur in exposed sections and wells. Sixty three oil and gas fields have been
discovered as of January 1989, which include two giant gas fields. The producing horizons are
sandstones of Cambrian, Permian, Jurassic, Cretaceous and Miocene ages and limestones of the
Paleocene and Eocene. As already stated, the proven recoverable reserves are nearly 777 million
barrelsofoil and 43TCFof gasof which about 488million barrels of oil and 15TCFof gas have been
consumed as of 2003. They divided the basin into large longitudinally oriented parallel tectonic
features which are as follows:

  Platforms:

(Tectonic Feature A). It is stable area founded on the Indianshield. Sedimentary rocks of Palaeozoic, Mesozoic and Cenozoic ages as well as recent alluvium are present here. Marine transgressions, regressions, overlaps and unconformities in the stratigraphic section provide evidence of sea-level fluctuation in response to local as well as world wide tectonic events.
Platform is subdivided into several sub zones such as follows:
    PunjabMonocline
    SukkharRift
    KandhkotMari Horst
    PannoAqilGraben
    JacobabadKhairpurHorst
   Sindh Monocline
Punjab Monocline: 
(AJ: It is a generally westward sloping monocline with its northern edge down warped to the north. The subsurface prolongation of the Sargodha High has shaped the Mianwali re-entrant. The part of the monocline north of Sargodha High contains a thin section of marine Palaeozoic and Tertiary strata, covered by Neogene fluviatile sediments. This part of the zone seems to have poor petroleum prospects. On the other hand southwest of Sargodha High, a vast gently dipping monocline contains considerably thick sediments of Palaeozoic, Mesozoic capped by Neogene flysch.This area containssalt pushedgentle anticlines. It has good prospects ofoil, gas and evidently, Nandipur and Panjpir gas fields have so far been discovered. Thus, Mesozoic sandstone playsappearsto offer exploration potential.
Sukkhar Rift:
On the basis of satellite imagery interpretation (Chaudhry, 1979), the central Sukkhar area of the platform is considered a faulted rift structure comprising a graben Panno Aqil graben) and two horsts ( Kandhkot-Mari and  Jacobabad-Khairpur horsts). The Panno Aqil graben is a continuation of the Cambay graben of India, which contains several oil and gas fields (Cambay, Anklesvar, Kalol, Navagan etc).The producing horizons are of Eocene, Miocene ages.
The Kandhkot-Mari horst:
Consists of Mesozoic, Tertiary and Quaternary sediments. This horst structure"Has produced gas in the Eocene carbonate with 4 TCF reservoirs. Mari gas field is considered a giant gas field. It is equated with Jasalmer Basin of India where same horizon of gas has been hit at few places in India.Another structure called Sindh structure east of Mari also extends into India but its main crest is in Pakistan.
The Jacobabad-KhairpurHorst:
started becoming a positive area in Late Jurassic. It consists of Mesozoic, Tertiary and Quaternary sediments with the Cretaceous and Jurassic truncated and reduced in thickness over the horst. Mesozoic and Tertiary plays are significant targets for exploration in the Jacobabad - Khairpur horst, because Eocene carbonate produced low methane natural gas at Khairpur and in Jacobabad structure.
                        In between the Kandhkot-Mari and Jacobabad Khairpur horsts lies graben area called Panno Aqil graben (AJ. This graben area also offers better chances for generation and accumulation of hydrocarbons. Oligocene/Miocene and Eocene reservoirs are within reasonable drilling depths if suitable traps(probably fault traps)are seismically delineated.

Sindh Monocline:(A2b)

The Sindh monocline is a gently sloping monocline of Mesozoic and Cenozoic sediments deposited on ashelf.The zone is delineated by the Lakhra uplift in the west and Nagar Parkar high in the east. Within this zone west of the Nagar Parkar high, a number of fields in the Badin area are producing oiland gas from the Cretaceoussands. The structures producing oil and gas in Badinarea are mainly fault traps related to LateMesozoicriftphase. Depressions (Tectonic Feature-B): Platform described above is followed to the west by a belt of depressions. As a consequence of coalescence of Indian and Eurasian plates, along with rotational movement of Indian Plate, a sever deformation of sediments has resulted near the plate boundaries

and a fold belt was raised with simultaneous creation of a belt of depressions on the flank. The deformation front is progressing from west to east and north to south. The western flanks of the depressions arc deformed and from east to west and south to north the structures become more complicated. The depressions are covered with thick Quaternary deposits characterized by the occurrence of multiple unconformities.