The Upper Assam Basin is a poly history basin from where hydrocarbons are being produced for more than a century. Geologic setting of Assam-Arakan basin. Assam –Arakan Basin Geological Setting: It includes Assam, Nagaland, Arunachal Pradesh, Manipur, Mizoram and Tripura. The eastern limit is. Unconsolidated Sand Stone Reservoir to Eliminate Sand Breakthrough Problem Having Active Aquifer Drive: A Detailed Case Study in Assam-Arakan Basin.
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Further increase in the clastic influx in the stable shelf during Late Eocene to Early Oligocene resulted in marine regression with the deposition of the upper part of the Kopili Formation, consisting of shales, siltstone and subordinate sandstones, in shallow marine to pro-delta environments.
In the North Bank of the Brahmaputra river, however, environmental conditions were deltaic with the deposition of sandstones with minor shales and siltstones. During this period, the Assam Shelf was being evolved in a passive margin tectonic setting and under shallow marine to brackish water sedimentation conditions.
Major aarkan elements of the basin are:. The major structural elements of the Assam—Arakan Basin and the salient features of each element are briefly described as following.
In the Borholla field of the Dhansiri valley and Champang field of the neighbouring schuppen belt, oil reserves occur in structurally controlled subtle trap in fractured basement rocks. The Lakadang Formation Early Eocene comprising limestone and coal bearing sandstones was deposited in shallow marine to lagoonal conditions, while the overlying Tura Sandstone Formation Early Eocene was deposited under fluvio-deltaic environment. This element contains most of the oil fields aralan the Upper Assam Shelf.
Organic matter is mainly humic and sapropelic. The shelf part rests on Precambrian granitic basement, whereas the basinal part lies on transitional to oceanic crust. East of the hinge zone, i.
Assam Arakan Basin | NDR – National Data Repository India
During Eocene to Oligocene, due to the rise of the peripheral arc system rise of the basement ridge consequent upon the active oblique subduction of the Indian plate, the intervening sea became progressively narrower southward.
The area within the Upper Assam shelf, having high petroleum potential, measures approximately sq km and contains about m thick sediments of mostly Tertiary period, and the area in the nasin part with moderate to high hydrocarbon potential measures about 60, sq km and contains more than 10,m thick sediments of mostly Tertiary period. Oil reserves in Kopili sandstones Upper Eocene are found mainly in the Geleki field. The closing of the trench system was also initiated in the northeast and then gradually progressed southward.
Zrakan the subthrust, the source sequences occur at basn depths and, therefore, should be in a higher state of thermal maturity.
Assam Arakan Basin
Organic matter richness of shales increases towards the Naga thrust. In this shelf—slope—basinal architecture, the hinge zone, at and across which the Upper Cretaceous-Eocene shelf facies changes over to basinal facies, is envisaged to lie below the Naga schuppen belt. The Himalayan Foredeep zone north of the Brahmaputra river lies in the northern periphery of the foredeep is overridden by the southerly moving thrust sheets of younger sedimentary rocks.
In the North Cachar area, exploration by deep drilling is yet to be initiated. The Shillong Plateau and Mikir hills Uplift, composed mostly of Precambrian granitic and metamorphic rocks.
From the Digboi, the shelf runs westward to the southern slope of the Shillong plateau.
This site is best viewed using current versions of Firefox v. It is envisaged that the undiscovered oil would continue to be found in structural, strati- structural and subtle traps in areas mostly bordering the Naga thrust and in the Naga Schuppen belt. The metamorphic complex occurs mostly to the east of the Indo-Myanmar international border.
Home Assam Arakan Basin. Following completion of collision and subduction of the oceanic part of the Indian plate during Late Oligocene to Early Miocene?
This foredeep was the site of deposition of the Surma Group of sediments under shallow marine lower part to brackish water upper part environments. Major tectonic elements of the basin are: Towards the close of Middle Eocene, limestone deposition ceased qssam of an increase in the influx of finer clastics in the shelf.
But, the Dhansiri Valley shelf, areas north of Lat. The Kharsang, Digboi and Champang oil fields are located in this element. The Indo-Burmese aswam system that developed during the oblique subduction of the Indian plate below the Burmese plate became the locus of deposition of Upper Disang shales under deep marine conditions.
In the Digboi and Kharsang oil fields, oil occurs in Tipam Arakzn and Girujan Clay formations, respectively, overlying the Naga thrust. Other significant milestones in oil exploration asasm Upper Assam were the discoveries of the Nahorkatiya, Moran and Rudrasagar oil fields inandrespectively. The basin covers an area of Sq. The sequences can be divided into bazin facies and basinal geosynclinal facies.
During the growth of these structures, the Girujan Clay Formation was deposited in the synclinal lows structural basins in Cachar area as indicated by seismic and well data from the Katakhal syncline of Cachar area where the Girujan Clay Formation is named as the Govindpur Formation.
It developed as a composite shelf-slope-basinal system under a passive margin setup during the period from Early Cretaceous to the close of Oligocene.
Some of the prominent faults, particularly those near the Naga thrust, are reverse faults, e. Geochemical analysis of exposed sediments from the Schuppen araan show a TOC range of 0. Oil within the Kopili Formation composed predominantly of shales with subordinate sandstone occurs in strati-structural combination traps, as in the Geleki field.
The Assam-Arakan sedimentary Basin is a shelf—slope—basinal system. The most prominent structural depression was formed in Kumchai — Manabhum area in front of the Mishmi uplift, where the Girujan Clay Formation attains a thickness of about m.
The Naga Metamorphic Complex, east of the Eastern thrust.