Download/Embed scientific diagram | Geological map of Cambay Basin, western India. from publication: Early Eocene equatorial vegetation and depositional. In the southern Cambay Basin, it was sourced from a higher plant fraction deposited in marine or fluvial deltaic environment (Sivan et al., ). It is based on the Sub-surface study of on oil field in Cambay basin. After a brief description of the Cambay basin’s geology, the other aspects of exploration were .
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Based on the cross trends the basin has been divided into five tectonic blocks. 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.
Throughout the geological history, except during early syn— rift bawinthe North Cambay Basin received major clastic inputs from north and northeast, fed by the Proto—Sabarmati and Proto—Mahi rivers.
In the northern part of the Ahmedabad-Mehsana Block, coal, which cambaay well developed within the deltaic sequence in Kalol, Sobhasan and Mehsana fields, is also inferred to be an important bazin source rock. The discovery of oil in Ankleshwar structure in gave boost to the exploration in the Cambay Basin. During Miocene The depocenters continued to subside resulting in the deposition of enormous thickness of Miocene sediments as the Babaguru, Kand and Jhagadia formations.
Seismic and drilled well data indicate a thickness of about 8 km of Tertiary sediments resting over the Deccan volcanics. The total volume of seismic reflection data acquired from the Geooogy Basin is of the order of LKM 2D and sq. The associated unconformity also helped in the development of secondary porosity.
These consist of sand size basalt fragments. This turned out to be a discovery well, which produced oil geoloogy gas. Subsidence of the basin resulted in the accumulation of a thick sequence of euxinic black shales cambayy subordinate coarser clastics.
The magnetic anomaly map also depicts the broad structural configuration of the basin. 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.
Pliocene was a period of both low and high strands of the sea level, allowing the deposition of sand and shale.
The end of the Paleogene witnessed geollgy major tectonic activity in the basin resulting in the development of a widespread unconformity. Oligocene — Lower Miocene marks another phase of tectonic activity with extensive deposition of coarser clastic sediments in the central and southern blocks.
Different Tectonic Zones with in the Basin The Cambay rift valley is bounded by well demarcated basin margin step faults. 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. During Pleistocene to Recent, the sedimentation was mainly of fluvial type represented by characteristic deposits of coarse sands, gravel, clays and cwmbay followed by finer sands and clays, comprising Geklogy Alluvium.
Besides this, localized sandstone reservoirs within the Cambay Shale as in the Unawa, Linch, Mandhali, Mehsana, Sobhasan, fields, etc are also present. In the following period, relative subsidence of the basin continued leading to the accumulation of the Younger Cambay Shale.
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. This shale sequence has been divided into Older and Younger Cambay Shale with an unconformity in between. 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.
These sediments are characterised by an assortment of illsorted, high energy trap derived materials. 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 same is true for the Tarapur Shale.
A total of more than 30, LKM of conventional data has been acquired. Gradually, the rift valley expanded with time. From north to south, the blocks are:. At places a gradational contact with the overlying Cambay Shale has also been noticed. The end of deposition of the Olpad Formation is marked by a prominent unconformity.
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.
Cambay Basin | NDR – National Data Repository India
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.
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.
Gsology than exploratory wells have been drilled in Cambay Basin.