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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But, the Dhansiri Valley shelf, areas north of Lat. These lateral tectonic movements were accompanied by upliftment and total withdrawal of the sea, heralding the onset of continental sedimentation the Tipam Sandstone Formation on the Assam Shelf as well as on the earlier basinal area.
The limestones with negligible impurities were, perhaps, deposited on sea mounds. Oil accumulations within the Bokabil Formation Middle Miocene in the Khoraghat and Nambar fields of the Dhansiri valley, occur assa structural combination traps. The development arakam the frontal foredeep in front of the rising Himalaya, during Mio-Pliocene and later times, due to tectonic loading by thrust slices was filled with coarser sediments.
In these grabens, a sequence of sandstones, shales and subordinate limestone towards top, assigned to the Khasi Group, was deposited in the southern slope of the Shillong Plateau, and a sequence of sandstone and shale, assigned to the Dergaon Group, was deposited in the Dhansiri valley. Major tectonic elements of the basin are:.
Home Assam Arakan Basin. In the Borholla oil field, oil occurs in fractured granitic basement rock of Precambrian age.
Assam Arakan Basin
All the oil and gas fields, discovered till date in the Upper Assam shelf, are situated mostly on the southeastern slope of the Brahmaputra arch, and almost all the major oil fields like Nahorkatiya, Lakwa, Lakhmani, Geleki, Dikom Kathaloni etc. The basinal geosynclinal part is occupied by the Cachar, Tripura, Mizoram and Manipur fold belts.
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.
The sequences can be divided into shelf facies and basinal geosynclinal facies. The Assam-Arakan basin witnessed two major phases of tectonic development. The closing of the trench system was also initiated in the northeast and then gradually progressed southward.
Cap Rock and Entrapment There are three well developed regional cap rocks within the Tertiary sedimentary succession, the lower one, occurring in the Upper Eocene is hasin argillaceous Kopili Formation, the middle one is the Barail Coal-Shale Unit and the upper one, overlying the Tipam Sandstone is the Girujan Clay.
Assam Arakan Basin | NDR – National Data Repository India
During the post- Oligocene time, however, different parts of the mega basin witnessed different evolutionary trends, mostly under compressive tectonic forces. A Comprehensive Petroleum System events of Assam basin.
The Kharsang, Digboi and Champang oil fields are located in this element. These clastics, making the lower part of the Kopili Formation, were deposited in open marine conditions during Late Eocene, when marine transgression was waning out. This foredeep was the site of deposition of the Surma Group of sediments under shallow marine lower part to brackish water upper part environments. Following the deposition of the Tura Sandstone, there was a wide spread marine transgression in which the Sylhet Limestone Middle Eocene was deposited almost all over the Upper Assam Shelf.
Geochemical analysis of exposed sediments from the Schuppen belt show a TOC range of 0. The average TOC ranges of different formations shale samples are as follows:.
The generalized stratigraphic succession.
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. During Paleocene, there was a marine transgression on the southern edge of the Shillong Plateau, depositing sediments of the Therria Formation consisting of limestone, sandstone and shale.
Most of the prominent faults continue upward into post-Tipam sediments, and the rest die out in the lower part of the Tipam Formation. In the Naga Schuppen belt, oil accumulations in the Lakshmijan and the Champang oil fields occur in that zone of the shelf which is overridden by the Naga thrust.
Assam Arakan Basin Basin Introduction:.
This site is best viewed using current versions of Firefox v. Oil reserves in Kopili sandstones Upper Eocene are found mainly in the Geleki field.
The Assam-Arakan sedimentary Basin is a shelf—slope—basinal system. Presence of pelagic fauna indicates that these sediments were deposited in shallow shelf to open marine conditions during Maestrichtian to Early Paleocene time.
In some of the exploratory wells, drilled in the southwestern part of the Dhansiri valley, good shows of oil have been observed in Eocene and Oligocene sands. The Naga Metamorphic Complex, east of the Eastern aarakan. Oil exploration in India commenced with the discovery of the Digboi oilfield in Upper Assam more than years ago, when, based on surface oil shows, a well was drilled on an exposed anticline, associated with the Naga thrust. Oil within the Girujan Clay Formation as in the Kumchai and Kharsang fields also occurs in combination traps, but here the control of lithology on accumulation is more than that assamm structure.
In this baasin 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 Girujan Clay being floodplain basib, the reservoir sands are generally lenticular and some what erratic in distribution. 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.