CAMBAY BASIN GEOLOGY PDF
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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More than exploratory wells have been drilled in Cambay Basin.
Cambay Basin Basin Introduction: In the following period, relative subsidence of the basin continued leading to the accumulation of the Younger Cambay Shale. During Paleocenethe basin continued to remain as a shallow depression, receiving deposition of cambqy, trap conglomerate, trapwacke and claystone facies, especially, at the basin margin under a fluvio—swampy regime.
During Early Eocenea conspicuous and badin transgression resulted in the deposition of a thick, dark grey, fissile pyritiferous shale sequence, known as the Cambay Shale.
The NW-SE Dharwarian tectonic trends gsology rejuvenated creating a ccambay rift graben extending from the Arabian sea south of Hazira to beyond Tharad in the north. 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. Out of prospects drilled, 97 are oil and gas bearing. These consist of sand size basalt fragments.
From north to south, the blocks are:. Different Tectonic Zones with in geo,ogy Basin The Cambay rift valley is bounded by well demarcated basin margin step faults. Subsequently, there was a strong tectonic activity that resulted in the development of the Mehsana Horst and other structural highs associated with basement faults. Reservoir Rock There are a number of the reservoirs within the trapwacke sequence of the Olpad Formation.
In the north, the basin narrows, teology tectonically continues beyond Sanchor to pass into the Barmer Basin of Rajasthan. The same is true for the Tarapur Shale. 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.
Gradually, the rift valley expanded with time. Subsidence of the basin resulted in the accumulation of a thick sequence of euxinic black shales with subordinate coarser clastics.
This site is best viewed using current versions of Firefox bain. Besides this, localized sandstone reservoirs within the Cambay Shale as in the Unawa, Linch, Mandhali, Mehsana, Sobhasan, fields, etc are also present.
The end of the Paleogene witnessed a major tectonic activity in the basin resulting in the development of a widespread 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. Shales within the Miocene section in the Broach depression might have also acted as source rocks. The discovery of oil in Ankleshwar structure in gave boost to the exploration in the Cambay Basin.
Pliocene was a period of both low geoloyy high strands of the sea level, allowing the deposition of sand and shale. 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. The associated unconformity also helped in the development of secondary porosity. During Miocene The depocenters continued to subside resulting in the deposition of enormous thickness of Miocene sediments as the Babaguru, Kand and Jhagadia formations.
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 hasin and clays, comprising Gujarat Alluvium.
Oligocene — Lower Miocene marks another phase of tectonic activity with extensive deposition of coarser clastic sediments in the central and southern blocks. At places a gradational contact with the overlying Cambay Shale has also been noticed.
Cambay Basin | NDR – National Data Repository India
The end of deposition of the Olpad Formation is marked by a prominent unconformity. 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. Geeology 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.
Based on the cross trends the basin has cakbay divided into five tectonic blocks. The total volume of seismic reflection data acquired from the Cambay Basin is of the order of LKM 2D and sq.
The Bouguer anomaly map has helped in identification of the major structural highs and lows in the basin. 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.
Seismic and drilled well data indicate a thickness of about 8 km of Tertiary sediments resting over the Deccan volcanics. Similarly, the Proto—Narmada river system was active in the south, supplying sediments from provenance, lying to the east. The end of Cambay Shale deposition is again marked by the development of a widespread unconformity that is present throughout the basin.
The magnetic anomaly map also depicts the broad structural configuration geoloy the basin. These sediments are characterised by an assortment of illsorted, high energy trap derived materials. The lithological heterogeneity gave rise to permeability barriers, which facilitated entrapment of hydrocarbons.
This shale sequence has been divided into Older and Younger Cambay Shale with an unconformity in between.