The Cambay rift Basin, a rich Petroleum Province of India, is a narrow, .. Throughout the geological history, except during early syn– rift stage, the North. Petroleum Geology of the Cambay Basin, Gujarat., India. Front Cover. L. R. Chowdhary. Indian Petroleum Publishers, – Petroleum – pages. Petroleum geology of the Cambay Basin, Gujarat., India. Responsibility: L.R. Chowdhary. Imprint: Dehradun: Indian Petroleum Publishers, c Physical.
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Geographic Location of the basin The Cambay rift Basin, a rich Petroleum Province of India, is a narrow, elongated rift graben, extending from Surat in the south to Sanchor in the north. In the north, the basin narrows, but tectonically continues beyond Sanchor to pass into the Barmer Basin of Rajasthan.
Seismic and drilled well data indicate a thickness of about 8 km of Tertiary sediments resting over the Deccan volcanics. The Bouguer anomaly map has helped in identification of the major structural highs and lows in the basin. The magnetic anomaly map also depicts the broad structural configuration of the basin. A total of more than 30, LKM of conventional data has been acquired. The total volume of seismic reflection data acquired from the Cambay Basin is ggeology the order of LKM 2D and sq.
This turned out to be a discovery well, which produced oil and gas. The discovery of oil in Ankleshwar structure in gave boost to geoloy exploration in the Cambay Basin. More than exploratory wells have been drilled in Cambay Basin. Out of prospects drilled, 97 are oil and gas bearing.
Different Tectonic Zones with in the Basin The Cambay rift valley is bounded by well demarcated basin margin step faults. Based on the cross trends the basin has been divided into five tectonic blocks.
From north to south, the blocks are:. Cajbay Early Tertiary geoloogy ranging in age from Paleocene to Early Eocene represent syn-rift stage of deposition that was controlled by faults and basement highs in an expanding rift system. These sediments are characterised by an assortment of illsorted, high energy trap geoloogy materials. Subsidence of the basin resulted in the accumulation of a thick sequence of euxinic black shales with subordinate coarser clastics.
The Middle Eocene witnessed a regressive phase with oscillating conditions of deposition and development of deltaic sequences in the entire basin. There was a regional southward tilt of beology entire rift basin during Late Eocene and it is marked by a regional marine transgression extending far to the north upto Sanchor basin.
Oligocene — Lower Miocene marks another phase of tectonic activity with extensive deposition of coarser clastic sediments in the central and if blocks.
The formation of the Cambay Basin began following the extensive outpour of Deccan basalts Deccan Trap during late Cretaceous covering large tracts of western and central India. The NW-SE Dharwarian tectonic trends got rejuvenated creating a narrow kf graben extending from the Arabian sea south of Hazira to beyond Tharad in the north.
Gradually, the rift valley expanded with time. During Paleocenethe basin continued to remain as a shallow depression, receiving deposition of fanglomerate, trap conglomerate, trapwacke and claystone facies, especially, at the basin margin under a fluvio—swampy regime. The end of deposition of the Olpad Formation is marked by camvay prominent unconformity.
Petroleum geology of the Cambay Basin, Gujarat., India in SearchWorks catalog
At places a gradational contact with the overlying Cambay Shale has also been noticed. During Early Eocenea conspicuous and widespread transgression resulted in the deposition of a thick, dark grey, fissile pyritiferous shale sequence, known as the Cambay Shale.
This shale sequence has been divided into Older and Younger Cambay Shale with an unconformity in between. In the following period, relative subsidence of the basin continued leading to the accumulation of the Younger Cambay Shale.
The end of Cambay Shale deposition is again marked by the development of a widespread unconformity that is present throughout the basin. Subsequently, there was a strong tectonic activity that resulted in the development of the Mehsana Horst and other structural highs associated with basement faults.
The end of this sequence is marked by a regressive phase leading to deposition of claystone, sandstone, and shale alternations and a limestone unit of the Dadhar Formation. The end of the Paleogene witnessed a major tectonic activity in the basin resulting in the development of a widespread unconformity.
During Miocene The depocenters continued to subside resulting in the deposition of enormous thickness of Miocene sediments as the Babaguru, Kand and Jhagadia formations. Pliocene was a period of both low and high strands of the sea level, allowing the deposition of sand and shale. During Pleistocene to Recent, the sedimentation was mainly of fluvial type represented by characteristic deposits of coarse sands, gravel, clays and kankar followed by finer sands and clays, comprising Gujarat Alluvium.
Throughout the geological history, except during early syn— rift stagethe North Cambay Basin received major clastic inputs from north and northeast, fed by the Proto—Sabarmati and Proto—Mahi rivers.
Similarly, the Proto—Narmada river system was active in the south, supplying sediments from provenance, lying to the east. In the northern part of the Ahmedabad-Mehsana Block, coal, which is well developed within the deltaic sequence in Kalol, Sobhasan and Mehsana fields, is also inferred to be an important hydrocarbon source rock.
The same is true for the Tarapur Shale. Shales within the Miocene section in the Broach depression might have also acted as source rocks. Reservoir Rock There are a number of the reservoirs within the trapwacke sequence of the Olpad Formation. These consist of sand size basalt fragments.
Cambay Basin | NDR – National Data Repository India
Besides this, localized sandstone reservoirs within the Cambay Shale as in the Unawa, Linch, Mandhali, Mehsana, Sobhasan, fields, etc are also present. Trap Rock The most significant factor that controlled the accumulation of hydrocarbons in the Olpad Formation is the favorable lithological geklogy with structural support and short distance migration. The lithological heterogeneity gave rise to permeability barriers, which facilitated entrapment of hydrocarbons.
The associated unconformity also helped in the development of secondary porosity. This site is best viewed using current versions of Firefox v. Cambay Bazin Basin Introduction: