geological propects of narmada, kutch and saurastra basin
Text of Narmada, kutch & saurastra basin
1. NARMADA, KUTCH & SAURASTRA BASIN BY: K.PRAMOD B.TECH 2ND YEAR RAJIV GANDHI INSTITUTE OF POETROLEUM TECHNOLOGY,RAE-BARELI
2. What is a sedimentary basin? A low lying area in the earth crust Basically tectonic in origin Sediments get deposited and accumulated
3. Areal extent of about 1.79 million sq. km. So far 26 basins have been recognized. In the deep waters beyond 200m isobaths, the sedimentary area has been estimated to be about 1.35 million sq.km. The unexplored area has come down to 15% which was 50% in 1995-1996 and the credits goes to DGH
4. On the basis of geological prospectivity, the basins of india have been divided into 4 categories Category 1: Proven commercial productivity
5. Category 2: Identified prospectivity Sedimentary basin with proved occurence of hydrocarbons but from which no commercial production of hydrocarbon has been occurred.
6. Category 3: Prospective basins Sedimentary basins with no significant oil and gas shows but which on geological considerations are considered as prospective.
7. Category 4: Potentially prospective Petroliferous basins with uncertain prospects which require basic data to be generated for prognosis. It includes the basins which bear an anology with similar hydrocarbon producing basins in the world and may be prospective.
8. KUTCH BASIN It forms the north-western part of the western continental margin of India. It is bounded by the Nagar- Parkar fault in the North, Radhanpur-Barmer arch in the east and North Kathiawar fault towards the south. The basin extents between Latitude 22 30' and 24 30' N and Longitudes 68 and 72 E covering entire Kutch district and western part of Banaskantha (Santalpur Taluka) districts of Gujarat state. The total area of the basin is about 71,000 sq. km of which onland area is 43,000 sq.km and offshore area is 28,000 sq.km. upto 200 bathymetry. The basin is filled up with 1550 to 2500m of Mesozoic sediments and 550m of Tertiary sediments in onland region and upto 4500m of Tertiary sediments in offshore region (Well GKH-1).
9. Saurashtra basin The basin is located in the northern part of western continental margin of India. The onland part of the basin is also known as Saurashtra Peninsula. This basin lies north of commercially proven Mumbai Offshore and south of highly prospective Kutch basin. The onland part of the basin borders with the commercially proven Cambay Basin on its eastern flanks. The deeper offshore Saurashtra borders with the Indus fan (to the abyssal plain of the Arabian Sea)
10. NARMADA BASIN It is the southern-most of the three marginal basins embayed into an arrow graben along the Narmada-Songeo fracture. The narmada rift basin crosses it in the Gulf of Cambay region at the widest part of the shelf, south of kathiawar bulge.
11. The evolution of the western continental-margin basins of India is related to the breakup of eastern Gondwanaland from western Gondwanaland in the Late Triassic / Early Jurassic and the subsequent spreading history of the Eastern Indian Ocean The western margin evolved through early rift and post rift phases of divergent margin development. A series of regional and local horsts and grabens resulted in response to rifting along the dominant basement tectonic trends (NNW-SSE, NE-SW and ENE-WSW). The northernmost part of the western continental margin was the first to be subjected to continental rifting and crustal subsidence in the Late Triassic The opening of the Kutch basin to the north of Saurashtra peninsula coincided with the transgressive phase of the sea onto the coastal areas of other parts of Gondwanaland including the western margin of Indian plate during Jurassic-Cretaceous time (Krishnan, 1960). KUTCH BASIN: GEOLOGICAL HISTORY:
12. Rifting along the Delhi trend and consequent subsidence of the block between the Nagar Parkar hills and the Saurashtra Peninsula in the Late Triassic initiated development of the Kutch Basin. The basin formed the site for westerly deepening epi-continental sea, probably an extension of the Tethys, in which thick pile of sediments, ranging in age from Middle Jurassic to Early Cretaceous, were deposited in shallow marine to deltaic environments. The sediments were deposited in two major cycles - a Middle Jurrasic transgressive cycle and a Late Jurassic - Early Cretaceous regressive cycle The Kutch basin is a pericratonic rift basin situated in the western margin of India. Nagar Parkar uplift in the north and Kathiawar uplift (Saurashtra horst) in the south respectively along Nagar Parkar and North Kathiawar faults delimit the EW rift
13. GEOLOGY AND TECTONIC EVOLUTION: The Kutch basin has a comprehensive Mesozoic package. It has about 3000m of sediments ranging in age from the Late Triassic to Lower Cretaceous. The basin was inundated by sea by the Middle Jurassic (Bajocian) times. The sediment package is predominantly siliciclastic with the carbonate sediments being mostly confined to the Bathonian. The siliciclastic sediments range from nearshore coarse-grained sands and conglomerates to storm-influenced shallow shelf silts and clays. The Kutch basin got rifted along this trend. Kutch rifting was initiated in the Late Triassic as indicated by continental Rhaetic sediments in the northern part of the basin(Koshal, 1975). In the early stages of India's northward drift away from Gondwana land, during Jurassic time, the Kutch basin was formed by subsidence of a block.
14. SAURASHTRA BASIN: GEOLOGICAL SETTING OF AN AREA: The Saurashtra peninsula is located in the western periphery of India in the state of Gujarat. Saurashtra is a pericratonic rifted passive margin basin comprising an onshore area of 52,000 km2 and a 20,000 km2 offshore extension into the Arabian Sea. The peninsula developed by rifting along the three intersecting Precambrian orogenic trends, the ENEWSW Narmada Son lineament, the west coast fault with the NNWSSE Dharwar trend and the NESW Delhi Aravalli trend,at different stages of evolution of the Indian sub- continent and their subsequent reactivation during the Mesozoic and Tertiary times. Bounded by major faults and rift basins, the northern limit of Saurashtra is marked by the faulted margin of Kutch and the southern coast runs parallel to the extension of Narmada geo-fracture. The Wadhwan Formation occurs as a marine tongue within an overall deltaic system. The Deccan Trap Formations occupy most of the exposed area of the Saurashtra.
15. PETROLEUM GEOLOGY: Expected reservoirs : (i) Cretaceous sandstone. (ii) Eocene-Miocene shelfel carbonates / reefal build up. (iii) Tertiary deep water sands (Indus Fan). Expected source rocks : Paleocene to Oligocene shales Expected cap rocks : Eocene to Early Miocene shales. CATEGORY OF THE BASIN: Category III (Prospective Basin).
16. AGE OF THE BASIN & SEDIMENT-THICKNESS: The oldest phanerozoic rocks in this basin are the Mesozoic rocks exposed in the north eastern part (Dharangdhara Formation) of this basin. However major part of the Saurashtra Basin (both on land& offshore) is covered by Deccan Traps which have hindered the exploration of Mesozoic Hydrocarbon targets. Rocks of Early Cretaceous are exposed in the on land part of the Saurashtra Peninsula (north eastern part of the basin). Late Cretaceous Early Paleocene Deccan Volcanics cover most of the Saurashtra Peninsula and the Tertiary sediments are exposed only on the periphery of the Peninsula.
17. TECTONIC HISTORY: Tectonic movements in the Tertiary were milder and cyclic. After the early Middle Miocene, the western margin as a whole experienced heavy influx of clastics and manifests basinward rapid shift of the shelf over considerably long distance to its present position. The principle tectonic elements in the offshore region are: Shelfal Horst-Graben Complex: lies between the coast and shelf margin trough. The shelf structural assemblage consists of a number of horsts & grabens. Shelf Margin Trough: This Is a narrow linear trough elongated parallel to the shelf edge. It lies between shelfal horst-graben complex to the east and Laccadive ridge to the west.
18. Laxmi Basin: This Is located between Laxmi ridge and Laccadive ridge. Consists of a series of pronounced linear magnetic anomalies.Total sedimentary cover in the Laxmi basin varies from 1250m on basement highs to 3000m in the depressions. Laccadive Ridge: I