• Bombay High is an offshore oilfield 165 kilometres (103 mi) off the coast of Mumbai, India, in about 75 m of water.[1] The oil operations are run by India's Oil and Natural Gas Corporation (ONGC).
• Bombay High field was discovered by an Indian oil exploration team operating from the seismic exploration vessel Academic Arkhangelsky[1] during mapping of the Gulf of Khambhat (earlier Cambay) in 1964-67, followed by a detailed survey in 1972.[1] The naming of the field is attributed to a team from a survey run in 1965 analysed in the Rashmi building in Peddar Road, Cumballa Hill, Bombay. The first offshore well was sunk in 1974.[1]
• Every oil resource rock requires Structural traps which are mainly salt dome, coral reefs, fault trap and fold trap. In case of Bombay High, the structure is a "north-northwest to south-southeast trending doubly plunging Anticline with a faulted east limb", 65 km long and 23 km wide",[1] and is the most probable reason to call it "Bombay High".

Geology

• This is a carbonate reservoir, the main producing zone, L-III, consisting of sedimentary cycles of lagoonal, algal mound, foraminiferal mound and then coastal marsh, capped by a post-middle Miocene shale.[2] Bombay High has three blocks separated by east-west trending faults, all three with different gas-oil contacts but approximately 1355 m deep.

Production

• As of 2004, it supplied 14% of India's oil requirement and accounted for about 38% of all domestic production.
• On 27 July 2005, a major fire destroyed the production platform, leaving at least 22 people dead despite rescue measures taken by the Indian Coast Guard. The platform accounted for 110,000 barrels per day (17,000 m3/d), or 15% of India's oil production. Rebuilding this is expected to take upwards of 4 months and estimated to cost around Rs. 1200 crore or US$300 million.
• ONGC approved construction of seven pipelines with risers and associated top-side facilities in MHN in April 2007. These pipelines are vital for optimum utilisation from Mumbai High.
• Crude oil produced from Bombay High is considered to be of very good quality as compared to crudes produced in middle east. Bombay High crude has more than 60% paraffinic content while light Arabian crude has only 25% paraffin.[4]
• In November 2009, output of Bombay High fields, that accounts for half of the India's domestic oil production, fell 5.3% to 347,197 barrels per day (55,199.9 m3/d).[5]
• As of 2018 the output of the field was 205,000 barrels per day (32,600 m3/d).

Key Facts:

• Lower Eocene-Paleocene sediments have very good source-rock characteristics and goodhydrocarbon generation potential throughout the basin, but quality and quantity of the organic matter deteriorated towards the peripheral area from the basinal lows.
• The organic matter is dominated byinput from terrigenous higher land plants. However, two potential source sequences are identified inthe lower Eocene-Paleocene sediments. Specific biomarkers, particularly the relative contributionfrom resinous plants, flowering plants, carbon isotopic composition and marine organic matter diagnostic biomarkers indicate that these sediments exhibit intervals with different organofacies.
• Oils of the Mumbai Offshore Basin can be broadly categorized into two groups based on their biomarkers distribution and stable isotopic composition.
• Group I oils containing only terrestrial organic matter from fluvial/fluvio-deltaic depositionalenvironment generally correlate with the lower Eocene-Paleocene source-rock extracts from thewells located in the peripheral area of the lows in each block. On the other hand, group II oils, whichcontain mixed type organic matter deposited in marginal marine conditions, correlate with the upper layers of the lower Eocene- Paleocene source sequences in the wells located in the central parts of the lows in each block.
• All oils in the field are at approximately the same level of thermal maturity and were expelledfrom sources that still retain significant generative potential. These oils are generated locally andhave not undergone long distance migration.
• Maturity modeling of vitrinite indicates that in general the sedimentary sequences of the PannaFormation started oil expulsion 18-30 Ma and peak oil expulsion 12 Ma and continues to presentday.

Exploration

• Exploration of the area in the late 1950's resulted in the 1958 discovery of the Cambay gas andcondensate field. In 1960, the giant Ankleshvar oil and gas field was discovered and through theremainder of the 1960's 11 more fields were discovered in the Cambay Basin (Yenne, unpub. data,1980).
• Offshore seismic data collected during the 1960's and early 1970's lead to the discovery of the province's largest field in 1974, the Bombay High offshore oil and gas field.
• The Bombay High field produces primarily from Miocene limestones and some sandstone reservoirs on a fault bounded block that underwent recurrent uplift from R8-11 Paleocene through Miocene time.
• There are nowover 165 fields in the province. Although there are no producing fields in the Kutch Basin,uneconomic quantities of oil and gas have been found there.

Future Prospects:

• The Kutch offshore and the outer shelf area are only lightly explored and mayhave potential for significant discoveries. Jurrasic and Cretaceous potential may also exist beneaththe trap deposits on the Saurashtra peninsula.
• Although few stratigraphic traps have been identifiedin the Eocene-Miocene Cambay Deltaic AU, that area holds good prospects for more stratigraphicaccumulations