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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The Bouguer anomaly map has helped in identification of the major structural highs and lows in the basin. These consist of sand size basalt fragments. In the north, the basin narrows, but tectonically continues beyond Sanchor to pass into the Barmer Basin of Rajasthan.
Subsidence of the basin resulted in the accumulation of a thick sequence of euxinic black shales with subordinate coarser clastics.
This shale sequence has been divided into Older and Younger Cambay Shale with an unconformity in between. At places a gradational contact with the overlying Cambay Shale has also been noticed. Throughout cambau 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 Baein rivers.
Similarly, the Proto—Narmada river system was active in the south, supplying sediments from provenance, lying to the east.
The lithological heterogeneity gave rise to permeability barriers, which facilitated entrapment of hydrocarbons. This turned out to be a discovery well, which produced oil and gas. Different Tectonic Zones with in the Basin The Cambay rift valley is bounded by well demarcated basin margin step faults.
More than exploratory wells have been drilled in Cambay Basin. 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. These sediments are characterised by an assortment of illsorted, high energy trap derived materials.
Pliocene was a period of both low and high strands of the sea level, allowing the deposition of sand and shale. The end of deposition of the Olpad Formation is marked by a prominent unconformity. Based on the cross trends the basin has been divided into five tectonic blocks.
The end of the Paleogene witnessed a major tectonic activity in the basin resulting in the development of a widespread unconformity. The end of Cambay Shale deposition is again marked by the development of a widespread unconformity that is present throughout the basin.
Shales within the Miocene section in the Broach depression might have also acted as source rocks. Besides this, localized sandstone reservoirs within the Cambay Shale as in the Goelogy, Linch, Mandhali, Mehsana, Sobhasan, fields, etc are also present. The discovery of oil in Ankleshwar structure in gave boost to the exploration in the Cambay Basin.
The Middle Eocene witnessed a regressive phase with oscillating conditions of deposition and development of deltaic sequences in the entire basin.
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. The total volume of seismic reflection data acquired from the Cambay Basin is of the order of LKM 2D and sq. Seismic and drilled well data indicate a thickness of about 8 km of Tertiary sediments resting over the Deccan volcanics.
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. Reservoir Rock There are a number of the reservoirs within the trapwacke sequence of the Olpad Formation. The NW-SE Dharwarian tectonic trends got rejuvenated creating a narrow rift graben extending from the Arabian sea south of Hazira to beyond Tharad in the north.
The magnetic anomaly map also depicts the broad structural configuration of the basin. The same is true for the Tarapur Shale. Cambay Basin Basin Introduction: 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. 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.
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.
Petroleum geology of the Cambay Basin, Gujarat., India in SearchWorks catalog
The associated unconformity also helped in the development of secondary porosity. Trap Rock The most significant factor that controlled the accumulation of hydrocarbons in the Olpad Formation is the favorable lithological change with structural support and short distance migration.
Oligocene — Lower Miocene marks another phase of tectonic activity with extensive deposition of coarser clastic sediments in the central and southern blocks. 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.
Out of prospects drilled, 97 are oil and gas bearing. Gradually, the rift valley expanded with time. This site is best viewed using current versions of Firefox v. In the following period, relative subsidence of the basin continued leading to the accumulation of the Younger Cambay Shale. There was a regional southward tilt of the entire rift basin during Late Eocene and it is marked by a regional marine transgression extending far to the north upto Sanchor basin.
The Early Tertiary sediments 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.
During Miocene The depocenters continued to subside resulting in the deposition of enormous thickness of Miocene sediments as the Babaguru, Kand and Jhagadia formations.
A total of more than 30, LKM of conventional data has been acquired. Subsequently, there was cakbay strong tectonic activity that resulted in the development of the Mehsana Horst and other structural highs associated with basement faults.
From north to south, the blocks are:.