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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The southeastern slope of the Upper Assam Shelf, southeast of the Brahmaputra arch, having local structural highs and lows, upto the Naga thrust, and vasin 8 to 10 km beneath the Naga schuppen belt.
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 Borholla oil field, oil occurs in fractured granitic basement rock of Precambrian age.
Assam Arakan Basin | NDR – National Data Repository India
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.
This foredeep was the site of deposition of the Surma Group of sediments under shallow marine lower part to brackish water upper part environments. The basin covers an area of Sq.
aarakan This site is best viewed using current versions of Firefox v. In the Digboi and Kharsang oil fields, oil occurs in Tipam Sandstone and Girujan Clay formations, respectively, overlying the Naga thrust.
The Andaman trenchwhich has been receiving mostly argillaceous sediments since, possibly, Upper Cretaceous-Paleocene, is the southward extension of the Indo — Burmese trench system.
The metamorphic complex occurs mostly to the east of the Indo-Myanmar international border. Most of these hydrocarbon traps, particularly those developed in post- Barail sediments, orient parallel to the Naga thrust.
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. In the Khoraghat and Nambar fields situated in southeastern part of the Dhansiri Valley, oil occurs in the Bokabil Formation Middle Miocene which is not developed towards north in the Brahmaputra valley.
A Comprehensive Bason System events of Assam basin. Continued indentation by the Indian plate caused westward propagation of tectonic forces, which in turn caused development of a decollement thrust at the base of the Upper Disang shales, and a number of synthetic thrust faults.
Towards the close of Middle Eocene, limestone deposition ceased because of an increase in the influx of finer clastics in the shelf.
Major tectonic elements of the basin are:. Barail Coal-Shale Unit in the Schuppen belt also form important source rock sequence. In the Khoraghat oil field bzsin Dhansiri valley, oil occurs in sandstone reservoirs within the Bokabil Formation Middle Miocene. 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.
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.
Assam Arakan Basin
During the post- Oligocene time, however, different parts of the mega basin witnessed different evolutionary trends, mostly under compressive tectonic forces. Oil accumulations within the Bokabil Formation Middle Miocene in the Khoraghat and Nambar fields of the Dhansiri valley, occur in structural combination traps.
The Assam-Arakan basin witnessed two major phases of tectonic development. East of the hinge zone, i. Assam Arakan Basin Basin Introduction:. From the Digboi, the shelf runs westward to the southern slope of the Shillong plateau. The average TOC ranges of different formations shale samples are as follows:. These lateral tectonic movements were accompanied by upliftment and total withdrawal of the sea, heralding the onset of continental sedimentation the Basi Sandstone Formation on the Assam Shelf as well as on the earlier basinal area.
In this shelf—slope—basinal architecture, the arakn 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. During Middle to Late Cretaceous, when the Indian plate was moving northward, a number of horst and graben features developed on the granitic crust in the southern slope of the Shillong Plateau and Dhansiri valley. 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 of structure.
Disang shales, occurring in association with ophiolites, are somewhat metamorphosed here.
The limestones with negligible impurities were, perhaps, deposited on sea mounds. During shallowing of the sea in the basinal area, the aswam sediments of the Barail Group were deposited under environments ranging from moderately deep marine to deltaic.
In the North Bank of the Brahmaputra river, however, environmental conditions were deltaic with the deposition of sandstones with minor shales and siltstones. Home Assam Arakan Basin.
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. The development of the frontal foredeep in front of the rising Himalaya, during Mio-Pliocene and later times, bason to tectonic loading by thrust slices was filled with coarser sediments.