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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The end of Cambay Shale deposition is again marked by the development of a widespread unconformity that is present throughout the basin. Pliocene was a period of both low and high strands of the sea level, allowing the deposition of sand and shale.
The same is true for the Tarapur Shale. 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. Oligocene — Lower Miocene marks another phase of tectonic activity with extensive deposition of coarser clastic sediments in the central and southern blocks.
Shales within the Miocene section in the Broach depression might have also acted as source rocks. These consist of sand size basalt fragments. In the following period, relative subsidence of the basin continued leading to the accumulation of the Younger Cambay Shale. This turned out to be a discovery well, which produced oil and gas.
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.
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. Subsequently, there was a strong tectonic activity that resulted in the development of the Mehsana Horst and other structural highs associated with basement faults. In the north, the basin narrows, but tectonically continues beyond Sanchor to pass into the Cqmbay Basin of Rajasthan.
Besides this, localized sandstone reservoirs within the Cambay Shale as in the Unawa, Linch, Mandhali, Mehsana, Sobhasan, fields, etc are also present. During Early Eocenea conspicuous and widespread transgression resulted in the deposition of a thick, dark grey, baskn pyritiferous shale sequence, known as the Cambay Shale. The discovery of oil in Ankleshwar structure in gave boost to the exploration in the Cambay Basin.
This shale sequence has been divided into Older and Younger Cambay Shale with an unconformity in between. From north to south, the blocks are:. The associated unconformity also helped in the development of secondary porosity. More than exploratory wells have been drilled in Cambay Basin. The end of deposition of the Olpad Formation is marked by a prominent unconformity. At places a gradational contact with the overlying Cambay Shale has also been noticed.
Geographic Location of the basin The Cambay rift Basin, a rich Petroleum Province geolpgy India, is a narrow, elongated rift graben, extending from Surat in the south to Sanchor in the north. Reservoir Rock There are a number of the reservoirs within the trapwacke sequence of the Olpad Formation.
Similarly, the Proto—Narmada river system was active in the south, supplying sediments from provenance, lying to the east. Trap Rock The most significant factor that controlled the accumulation geoogy hydrocarbons in the Olpad Formation is the favorable lithological change with structural support and short distance migration.
The Middle Eocene witnessed a regressive phase with oscillating conditions of deposition and development of geolofy sequences in the entire basin. In the northern part of the Basln 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.
Subsidence of the basin resulted in the accumulation of a thick sequence of euxinic black shales with subordinate coarser clastics. During Miocene The depocenters continued to subside resulting in the deposition of enormous thickness of Miocene sediments as the Babaguru, Kand and Jhagadia formations. Cambay Basin Basin Introduction: Throughout the geological history, except during early syn— rift stagethe Cwmbay Cambay Basin received major clastic inputs from north and northeast, fed by the Proto—Sabarmati and Proto—Mahi rivers.
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 lithological heterogeneity gave rise to permeability barriers, which facilitated entrapment of hydrocarbons. 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 Bouguer anomaly map has helped in identification of bssin major structural highs and lows in the basin.
Cambay Basin | NDR – National Data Repository India
Out of prospects drilled, 97 are oil and gas bearing. The end of the Paleogene witnessed a major tectonic activity in the basin resulting in the development geklogy a widespread unconformity.
Based on the cross trends the basin has been divided into five tectonic blocks. The magnetic anomaly map also depicts the broad structural configuration of the basin. Seismic and drilled well data indicate a thickness of about 8 km of Tertiary baein resting over the Deccan volcanics. During Pleistocene to Recent, the sedimentation was mainly of fluvial bsain represented by characteristic deposits of coarse sands, gravel, clays and kankar followed by finer sands and clays, comprising Gujarat Alluvium.
These sediments are characterised by an assortment of illsorted, high energy trap derived materials. Different Tectonic Zones with in the Basin The Cambay rift valley is bounded by well demarcated basin margin step faults.
The total volume of seismic reflection data acquired from the Cambay Basin is of the order of LKM 2D and sq.