Proc Indian Natn Sci Acad 82 No. 3 July Spl Issue 2016 pp. 881-903  Printed in India. DOI: 10.16943/ptinsa/2016/48491 Status Report Petroleum Exploration in India - A perspective and Endeavours AJAY KUMAR DWIVEDI* Director (Exploration), Oil and Natural Gas Corporation Ltd, Jeevan Bharathi Building, New Delhi, India (Received on 15 May 2016; Accepted on 25 June 2016) Indian oil industry has come a long way since the first oil discovery at Digboi in 1889 through concerted exploratory efforts. Production of oil from a 5 barrels per day level from a single field in Assam has grown to more than 750000 barrels per day from over 50 major oil and gas in seven sedimentary Basins and is projected to attain 1 million barrels per day mark in near future. After Independence, oil and gas exploration was accorded high priority and was taken up by National, Private and International oil companies across the 26 sedimentary Basins covering an area of about 3.14 million sq. kms. Of the 26 sedimentary Basins, 7 Basins are producing oil and gas today. Sedimentary Basins of India are categorised into four categories based on their degree of hydrocarbon prospectivity as presently known. At present India’s estimated hydrocarbon resource is of the order of 28 billion tonnes of oil equivalent (BTOE) and an Initial In-place volume of about 11.18 billion tonnes of oil equivalent (BTOE). A project for re-assessment of the resource potential of Indian Sedimentary Basins has been initiated by Government of India with active participation of ONGC, OIL and DGH in view of extensive availability of new data from all the Sedimentary Basins. Currentefforts are to enhance the production from category–I Basins with a focus on upgrading the Category-II Basins to Category-I Basins. Present paper outlines the endeavours during last few years through opening up of new areas, especially frontier areas of Proterozoic Basins of Vindhyan and Satpura, Deep offshore Basins of Bay of Bengal and Arabian Sea within Indian exclusive economic zone, Andaman fore-arc and back-arc Basins, unconventional sources of hydrocarbons such as Basement exploration, CBM (Coal Bed Methane), shale oil and gas, gas hydrates and leveraging the technology advances in Petroleum exploration. Keywords: Petroleum; Resources; Reserves; Category; Basins; NELP; Frontiers; Unconventional Introduction in discovery of more than 830 oil and gas fields including 50 major fields with an increase in production Quest for Petroleum in India spans over 162 years from an insignificant 5 bopd from a single field in since the first lease given in Assam by British Assam to present production of 750000 bopd across government during 1854. A new chapter and the country. Independent India witnessed an enhanced challenging journey of Indian upstream Petroleum exploratory activity in its sedimentary Basins by the industry began with discovery of oil from the historic then newly created National Oil Companies leading first well Digboi No:1 in 1889 barely 30 years after to opening up of new Petroliferous Basins of Cambay, the first Drake Oil well was drilled by Col. E L Drake Rajasthan, Assam & Assam-Arakan fold Belt, the in Northwest Pennsylvania, USA. Indian upstream prolific Western Offshore, Krishna-Godavri and industry since then has travelled a long way through Cauvery Basins. The spectacular achievements by various socio-political changes and surged ahead with these NOC’s have brought India into the World Oil the economic growth of the country. Growth of Indian Map. Sustained exploratory efforts by National Oil economy and the development of the upstream companies coupled with the initiatives by GOI in terms industry have always moved hand in hand. Sustained of New Exploration License Policy (NELP) has efforts by the Indian upstream industry have resulted opened up the industry for exploration by International *Author for Correspondence: E-mail: [email protected] 882 Ajay Kumar Dwivedi Oil and gas companies, as well as Private oil increase in 3D seismic data acquisition led to many companies. As on date the Indian E&P industry is discoveries in challenging environments. Drilling of operated by over 117 companies consisting of 11 the deeper exploratory wells resulted in refining the PSU’s, 58 Indian Private Companies and 48 geological models of the existing Basins and better International/Foreign Oil and Gas Companies targeted understanding of their tectonic styles, sedimentation to explore the 26 sedimentary Basins covering an area pattern and evolution. of 3.14 million square kilometres, including the deep Biswas et al. (1993) for the first time published water areas beyond 400m bathymetry. a comprehensive classification of Indian sedimentary Exploratory efforts by these companies resulted Basins using the Dickinson (1976) scheme of Basin in accreting about 11187 MMTOE of in place classification based on the structural style, geometry hydrocarbon volume by 2015, an increase of 32% as and size, nature of stratigraphic fill and thermal history compared to base year of 2006. into 38 sedimentary Basins and grouped them in three main settings: (i) intracratonic, (ii) rifted, (iii) orogenic India’s demand for fossil fuel by 2040 is settings (Table 1) and regrouped into 26 sedimentary estimated to grow by CAAGR (Compounded Annual Basins based on the hydrocarbon proclivity. Average Growth Rate) of 3.6% for oil and 4.6% for natural gas to keep pace with the projected economic Most of the Indian Sedimentary Basins are growth. The oil import dependency of the India is pericratonic, bordering the Indian plate radially. The predicted to rise to 90% from the current 70%. To northern Basins are bordered by orogenic belts of meet the increasing energy demand Government of Himalaya and Assam–Arakan and are the peripheral India has adopted several policies such as opening foreland Basins sub ducting under the orogenic belt. up of upstream exploration through competitive bidding The coastal pericratonic Basins, especially in the south under NELP during 1997-98, marginal field policy are extending from onshore to offshore and are rifted during 2015 and is now moving towards Open Basins, separated by horsts. The Intracratonic Basins Acreage Policy model for future acreages under are rift Basins such as Gondwana Basins/grabens or Hydrocarbon Exploration Licence Policy (HELP). structural depressions such as Vindhyan, Cuddapah, Kaladgi and Bhîma Basins. An overview of the status of exploration in the petroliferousBasins of India, their future perspective Petroleum occurs mainly in the marginal and and the endeavours carried out by Indian E&P pericratonic rift Basins. Occurrence of commercial companies, especially Indian NOC’s leveraging the petroleum from the northern foreland Basin is yet to advances in the technology for establishing producible be established excepting in the Upper Assam inter- hydrocarbons has been presented in the following orogenic foreland Basin – Assam Shelf situated on paragraphs. cratonicwedge between Himalayan and Assam– Arakan mountains. Tectonic setting and collision of Sedimentary Basins of India the Indian plate created favourable habitat for generation and preservation of thehydrocarbons. Exploratory efforts since 1850’s by foreign private oil Hydrocarbon discoveries from the Interior and Intra- companies (Assam Railways and Trading Company cratonic rift Basins are so far elusive barring few gas Limited (AR&T), Assam Oil Company (AOC) and indications; however, recent exploratory efforts are Burma Oil Company (BOC) and later by NOC’s from indicating encouraging results such as gas discovery late 50’s and subsequently by private/foreign from Proterozoic VindyanBasin. companies (1980) has resulted in expanding the geological knowledge of the Indian sedimentary Basins The estimated prognosticated resource base of and about 88% Basinal areas are at various stages the Indian Basins is 28 BMTOE including the 7 of exploration (DGH, 2011). These efforts have also BMTOE from deep water sector. As on 2015, aided in working out a scheme of tectonic exploratory efforts have resulted in estimation of Initial classification of the Basins (Biswas et al., 1993, Hydrocarbon In-Place (IHIP) of about 11.18 BMTOE Biswas, 1998, Ravi Bastia et al., 2007) that was which is about 40% of the present prognosticated required for the detail Basin analysis. Multifold resources. Reassessment of the hydrocarbon Petroleum Exploration in India - A perspective and Endeavours 883 Table 1: Classification of Indian Sedimentary Basins (After Biswas et al., 1993) Category Type Basins Status I. Interior Basins Intra-Cratonic Sags 1. Vindhyan Basin Gas Indications 2. Chattisgarh-Bastar Basin 3. Cuddapah Basin 4. Kaladgi Basin II. Rifted Setting II Marginal Aulacogen 1.Cambay Basin Oil and Gas producing Basin A II Pericratonic Rift 1.Kutch Basin Oil and Gas – Emerging Basin B 2.Saurashtra Shelf Oil and Gas Indications 3.Surat Basin 4.Bombay-Ratnagiri Basin Oil and Gas producing Basin 5. Konkan Basin 6. Kerala Basin 7. Western Bengal Basin 8. Mahanadi Basin Gas discoveries – Emerging Basin 9. Krishna-Godavari Basin Oil and Gas producing Basin 10. Palar Basin 11. Cauvery Basin Oil and Gas producing Basin 12. Mannar Basin II Intra-Cratonic RM 1. Pranhita-Godavari Basin C 2. Mahanadi Graben 3. Purnea Graben II Intra cratonicTranstensional 1.Satpura Basin D Basins 2. Son Basin 3. South Rewa Basin 4. Damodar Basin 5. Narmada Basin II Miogeoclinal Prism 1. Deep Water Basins of West coast E 2. Deep water Basins of East coast Oil and Gas Producing Basins III. Orogenic Settings III Superposed Basins 1. Karewa Basin A III Peripheral Foreland Basin 1. Rajasthan Basin Oil and Gas Producing Basin B 2. Punjab Basin 3. Ganga Basin 4. Lower Assam Basin Oil and Gas Producing Basin III Inter-orogenic foreland Basin 1. Upper Assam Basin Oil and gas Producing Basin C III Forearc Basins 1. Kohima forearc Basin D 2. Tripura-Mizoram Forearc Basin Gas producing Basin 3. Andaman Basin Gas Indications III Remnant Ocean Basin 1. East Bengal Basin E resources of all the Indian sedimentary Basins Exploratory activities for hydrocarbons in the including the deep water areas has been taken up 26 sedimentary Basins were initiated as early as mid- and is in progress. 50’s and are continuing with varying degree of success. 884 Ajay Kumar Dwivedi These Basins were grouped under four major Depending upon the exploration results, Basins categories of I to IV (Rai et al., 1998) (Table 2, Fig. are upgraded. The number of category–I Basins rose 1) based on the exploration success and from a single Basin in 1956 (Upper Assam Shelf) to commerciality. the current 7 producing Basins due to sustained Fig. 1: Map of PetroliferousBasins of India showing the categories (after DGH) Petroleum Exploration in India - A perspective and Endeavours 885 Table 2 :Category of PetroliferousBasins of India Category Basis for categorization of Sedimentary Basins in India I Proven Petroliferous Basins with commercial production Assam Shelf, Cambay, Rajasthan, Assam-Arakan fold belt, Mumbai Offshore, Krishna-Godavari and Cauvery Basins. II Proven Petroliferous Basins awaiting commercial production Kutch, Mahanadi-NEC (North East Coast), Basin, Andaman-Nicobar Basins. III Basins geologically considered prospective with hydrocarbon shows Himalayan Foreland Basin, Ganga Basin, Vindhyan Basin, Saurashtra Basin, Kerala Konkan Basin, Bengal Basin. IV Frontier Basins which are either poorly explored or having inadequate geological information or are rated poor based on present concepts and knowledge of petroleum geology but considered prospective by analogy with similar Basins in the world Karewa Basin, Spiti-Zanskar Basin, Satpura–South Rewa– Damodar Basin, Chhattisgarh Basin, Narmada Basin, Deccan Syneclise, Bhima-Kaladgi, Bastar Basin, Pranhita-Godavari Basin, Cuddapah Basin exploratory efforts aided with the right technology The North Assam Shelf is extensively explored implementation. block of Assam Shelf. Exploration efforts of Fold Belt progressed from anticlinal crest to target subtle The present paper deals with brief geological structural and geomorphic anomalies viz. Agartala set-up, plays established and recent endeavours to Dome and Banskandi structure based on aerial photos, enhance success ratio. remote sensing studies and limited 2D seismic data, yielding fair amount of success. Assam Shelf, Assam-Arakan Basin (Category-I Basin) Hydrocarbon Plays - Established and New Plays The onshore Assam & Assam-Arakan Basin located Oil and gas are established from clastics reservoirs in the north-eastern part of India is a poly history Basin of Mio-Pliocene- Girujan, Miocene -Tipam, Oligocene which evolved in response to the movement of the –Eocene –Barails, Mid-Upper Eocene –Kopilli, Indian plate in relation to the Eurasian and Burmese Lower Eocene –Lakadong and Therria and from the plates. The Assam, Assam –Arakan Basins cover an fractured Archean Basement. The Miocene – area of about 116000 sq.kms. Tectonically, the Assam Oiligocene –Tipam and Barail Formations contain & Assam Arakan Basin has been subdivided in to most of the discovered oil. two major Basins viz., Assam Shelf & Assam-Arakan Fold Belt. Part of the Assam Shelf lying to the north Exploration of deeper plays (Tura and and south of the E-W trending Jorhat Wrench Zone Basement) has been a major challenge in the Assam has been designated as North Assam Shelf and the Shelf. Tura play (Palaeocene) is an exciting horizon Dhansiri Valley (South Assam Shelf) respectively (Fig. in terms of deeper prospect exploration in entire North 2). Assam Shelf and has potential to emerge as a significant play. Recent exploratory efforts by NOC’s The North Assam Shelf constitutes platform part has resulted in risk-reward perception of Tura play of the Basin and represents the shelfal front. The and identification of prospects in Lakwa and Geleki Fold Belt of northeast India is a part of the outer wedge fields in the northern part of Assam Shelf. There has of the Indo-Burmese Arch. It runs through states of been significant achievement in establishing fractured Arunachal Pradesh (North Eastern part of Naga- Basement and Kopili plays (Eocene) in southern part Patkai hills), Nagaland (Naga-Patkai hills), Assam of the Assam Shelf in Khoraghat area which has (North Cachar hills and Cachar), Manipur (Laimatol opened up new area for exploration of deeper plays Range), and Mizoram (Mizo hills) and to the west in the Assam Shelf. open folds of Chittagong-Tripura Hill tracts. Structural complexities and difficult terrain are an integral part New age data sets continued to consolidate the of Fold Belt, which have influenced the exploration Miocene - Tippam Sands and the Barail Play inputs and exploration strategy for this area. (Oligocene) with identification of new exploration 886 Ajay Kumar Dwivedi Fig. 2: Tectonic Map of North-eastern India (after ONGC) prospects. In the southern part of Assam Shelf Sylhet a narrow, elongated rift graben, extending from Surat and Kopili plays are well established in Borholla- in the south to Sanchor in the north. In the north, the Champang fields and remain elusive in the rest of Basin narrows, but tectonically continues beyond Dhansiri Valley.Taking these leads into consideration Sanchor to pass into the Barmer Basin of Rajasthan. the focus of exploration is for establishing for Sylhet On the southern side, the Basin merges with the and Barail plays in the Assam-Arakan Basin. Bokabil Bombay Offshore Basin in the Arabian Sea (Fig. 3). play continue to be an attractive stratigraphic Since the discovery of first exploratory well on Lunej exploration play in southern part of Assam Shelf. In structure near Cambay in 1958, more than 2300 wells Fold Belt, elusive “Badarpur Oil Play” remains to be have been drilled in the Basin by various companies. elusive for oil though few gas discoveries are Hydrocarbon Plays - Established and New Plays reported. Naga up thrust Tipam Section has emerged as one of the attractive play in the north Assam shelf. The evolution of Cambay Basin from the petroleum Similarly the basement exploration in Khoraghat area point of view is fairly well understood and hydrocarbon has been rejuvenated with use of new technology accumulations are known in all sequences ranging DFN modelling (Discreet Fracture Network) and from Paleocene to Miocene. Major accumulations are drilling of horizontal wells. known in Middle Eocene structural traps over block uplifts and block edge folds. A few combination traps Cambay Basin (Category: I Basin) along block boundaries and over structural noses also The Cambay rift Basin covering an area of about occur. Early to Middle Cambay Shale has been 53,500 sq. km. is a Category-I Basin and encompasses established as major source rock,middle Eocene Petroleum Exploration in India - A perspective and Endeavours 887 Fig. 3: Tectonic map of Cambay Basin (after ONGC) 888 Ajay Kumar Dwivedi deltaic sands are major reservoirs and Late Eocene- low risk/moderate reward category. Growth in oil and Oligocene and Miocene Shales are regional cap rock gas production expected from a combination of new in this Basin. The Broach depression in Broach block field discoveries and effective management of existing is the largest kitchen area for maturation of source acreage. rocks and the generation of hydrocarbons. Transverse Rajasthan Basin (Category: I Basin) highs played an important role in controlling the palaeo- drainage and distribution of sands. Most of the troughs The 1,26,000 sq. km of Recent sediment covered area are local generation centres for accumulation in the to the west of Aravalli up to Pakistan border which is adjacent highs. There are several petroleum systems a part of the Thar desert, is designated as the Rajasthan in the Basin and the most important one is the peripheral foreland Basin (Biswas et al., 1993). It is Cambay-Hazad Petroleum System(!) which is related a part of the Indus Foreland. It is divided into four to several large oil and gas fields. sub-basins/sectors (Fig. 4) viz., (i) Jaisalmersub-basin (JB) on the north western slope of the Jaisalmer-Mari The Cambay-Hazad(!) petroleum system in basement arch (JMA), (ii) Bikaner-Nagaur (BN)sub- South Cambay Basin, has original in-place oil and gas basin on the northeast flank of the arch, (iii) Shahgarh- reserves of 395 million tonnes. The system covers Miajlar (SM) sub-basin southwest of the arch and 9320 km² encompassing 20 different oil and gas (iv) Barmer-Sanchor (BS) sub-basin south of the arch accumulations. Carbon isotopic and biological marker (extension of Cambay Basin). Recent discoveries of data indicate that the low sulphur, high API gravity oil oil and gas from this Basin have enhanced the originated from the lower-middle Eocene Cambay prospectivity perception. Shale source rock. Burial and thermal history reconstructions indicate that oil generation and Barmer–Sanchor sub-basin is a lacustrine failed migration occurred from Miocene (21 Ma) to Recent. rift comprising the sedimentary sequence of more than The overburden rocks are over 3 km thick and range 6 km ranging in age from Mesozoic to Cenozoic with in age from middle Eocene to Recent. The principal prolific Eocene source rocks. High quality reservoirs reservoir rocks are sandstone units of the Hazad and are encountered in the Upper Cretaceous- Ardol Members of the Ankleshvar Formation. Paleocenesyn rift deposits. Number of oil and gas discoveries like Saraswathi, Rageshwari, The essential elements of the petroleum system, Kameshwari, Mangala, Aishwarya, Shakti, Bhagyam consisting of the source, reservoir, seal and overburden rocks were deposited from early Eocene to Recent time and the critical processes of generation, migration, trap formation, and accumulation occurred from Miocene to Recent. Although it is usually the new discoveries that capture the attention of the oil industry, 70% of the hydrocarbon liquids produced in the world today actually come from fields that have been in operation for more than twenty years: the majority of petroleum assets consist of “old” fields. With most of the world’s potential oil provinces having already been explored and major new discoveries becoming increasingly rare, mature fields are slated to play an ever more prominent role in energy supply. Currently exploration of the Cambay rift Basin is in matured stage and bears a good chance of maximizing the probabilities of discovering small fields in subtle traps. As most of the large accumulations have been located, the Basin is now being rated as Fig. 4: Sub-basins of Rajasthan Basin (after ONGC) Petroleum Exploration in India - A perspective and Endeavours 889 are some of the significant fields in Barmer-Sanchor Western Pericratonic Rift Basins sub-basin. The Basins of western continental margin of India Hydrocarbon Plays - Established and New Plays (WCMI) situated on the western passive margin of the Indian plate evolved during the separation of The Jaisalmer sub-basin is a Late Palaeozoic-Mesozoic Madagascar-Seychelles in Late Cretaceous between Basin with Permian rocks resting unconformably over 90 Ma and 65 Ma. The rifting started in Late the Proterozoic Basement with gas discoveries of Cretaceous with syntectonic Deccan volcanic activity Manhera Tibba, Ghotaru Extn-I, South Kharatar, that continued till Early Paleocene. Early Paleocene ChinnewalaTibba and BakhriTibba fields. The to Early Eocene hiatus was the period of the rift-drift Bikaner-Nagaur sub-basin to the north has widely transition marked by a widespread unconformity in differing geological histories during Palaeozoic and all the Basins. The post-rift thermal cooling resulted Mesozoic times. This Basin has well developed Infra- in sagging and the Basins evolved into a marginal sag Cambrian sequence. The Shahgarh-Miajar sub-basin initiating marine transgression. is mainly Mesozoic Basin with thin cap of Palaeocene- Eocene rocks (300m) and a thin (200m) base of Coast parallel Ridge-Depression couplets, Kori- Permian rocks resting over the basement. Comorin Ridge/Depression and Laxmi-Laccadive Ridge/ Depression, crossed by first order transverse The Rajasthan Basin is mostly covered by desert basement arches are the major features of the WCMI sands excepting on the Jaisalmer-Mari basement arch structure (Biswas, 1989) (Fig. 5). The transverse (JMA) which is the only outcropping region besides a few scattered ones. Sequence from Middle Jurassic to Early Eocene is exposed in Jaisalmer sub-basin. Apart from Barmer sub-basin, there is no Tertiary prospect in other sub-basins of Rajasthan. Excepting small satellite pools in the Paleocene section, the chance of another large discovery appears to be low. However, the Barmer discoveries indicate that the prospect of sizeable accumulation in Sanchor sub- basin cannot be ruled out. In Shahgarh-Miajar sub- basin, the Mesozoic are the main prospective targets, particularly the Cretaceous Pariwar, Goru, and Parh Formations. Deeper Cretaceous and Jurassic targets should be the primary focus in Shahgarh-Miajar sub- basin. In Jaisalmer sub-basin focus should be on combination and subtle traps in Jurassic and Lower Cretaceous plays, while more extensive exploration for heavy oil should be planned for the Bikaner-Nagaur sub-basins. In Jaisalmer sub-basin, deeper Mesozoic plays like Baishakhi Badesir, Jaisalmer and Lathi of Jurassic age will form frontier plays. The finer clastics along with thin irregular sand bodies within Basisakhi Badesir Formation deposited in sub tidal to inner shelf Fig. 5:Tectonic map of Western Continental Margin of India environment may form stratigraphic/strati-structural (modified after Biswas, 2008b) 1: Saurashtra Arch; 2: prospects which are targets for future exploration. Bombay Arch; 3: Vengurla Arch; 4: Tellicherry Arch. Similarly, the thick Jaisalmer limestone with occasional Basin positions: - N of 1- Kutch Basin, Between 1 & 2: Surat Depression, 2 & 3: RatnagiriBasin, 3 & 4: oolitic development may be another suitable promising Kankan Basin, S of 4: Kerala Basin. SHG-Complex: exploration objective. Shelfal horst graben complex (after ONGC) 890 Ajay Kumar Dwivedi arches, from north to south are, Saurashtra, Bombay, alignment of structural elements, the Basin is Vengurla and Tellicheri arches which divide the shelf subdivided in to six major units, three of which are into five offshore sub-basins - Kutch, Surat, Ratnagiri characterised by paleo-platform set up, viz. the (Bombay offshore Basin), Konkan and Kerala Basins Mumbai High-DCS platform, the Heera-Panna- (Biswas and Singh, 1988). Kori-Comorin couplet Bassein Platform and the Ratnagiri platform which marks the edge of the present continental shelf, which were dominantly filled up by carbonate sediments. is rifted developing a “shelfal horst-graben” complex. Three of the other units, viz. Murud low, Saurashtra Each sub-basin extends offshore across the shelf, rise- Diu depression and Surat depression are mostly depressions and ridges. Thus, a shallow shelfal horst- characterised by clastic sedimentation acting as the graben complex, a shelf margin depression and ridge, dominant hydrocarbon generation centers for the a deep slope-parallel depression and an outer ridge Basin. The Tapti-Daman block is a clastic Basin (Laxmi) separating the Basin and abyssal plain are developed in the northern part of Bombay Offshore the characteristic structural domains of each sub- Basin in front of a narrow Cambay Gulf having basin. Kerala, Konkan and Ratnagiri Basins are sedimentation history from Paleocene time onwards. confined to offshore. The West Coast Fault terminates Middle Eocene-Oligocene deltaic sediments of proto- these Basins along the coastline. Narmada in Cambay Basin and Late Oligocene- Miocene sediments in Tapti-Daman sector deposited Of the five sub-basins, Surat and Ratnagiri as a result of progradation of the delta through the (Bombay) offshore Basins qualify as a Category-I narrow Cambay Gulf. Basins with its vast reserve of hydrocarbon contributing almost 70% of India’s total oil/gas Continued and sustained exploratory and production. Kutch Basin is Category-II Basin waiting development efforts in Mumbai Offshore Basin since to be upgraded in view of commercial discovery. last four decades have shown remarkable results and led to conversion of nearly 50% of the prognosticated The Kerala-Konkan Basin though well explored resource of 9190 MMToE in to In-place volume of no commercial accumulation could be located till date. hydrocarbons. Awaiting discovery, this Basin is listed in Category- III Basins. Hydrocarbon Plays - Established and New Plays Mumbai Offshore Basin (Category-IBasin) The major hydrocarbon fields of the Basin include Bombay High, Bassein, Panna, Mukta, Neelam, The Mumbai Offshore Basin is the most prolific of all Heera, South Heera, Ratna, D-1 fields, Tapti (north, the hydrocarbon bearing provinces in India. mid and south), C22/24 structures. Bounded by Diu and Narmada Faults and Hydrocarbon accumulations in BH-DCS-HPB Deccan Trap outcrops to its north and east, the (Bombay High–Deep Continental Shelf–Heera- pericratonic Mumbai Offshore Basin extends towards Panna-Bassein) sector are structurally controlled, in west parallel to the western continental margin of India general occur, in carbonate reservoirs ranging in age up to the Western Margin Basement Arch. NE-SW from Middle Eocene to Middle Miocene with a few trending Vengurla Arch separates the Basin from the exceptions of stratigraphic/combination plays in clastic Kerala-Konkan Basin to its south. reservoirs. While major pay zones occur in Middle On the basis of structural elements and the Eocene and Early Miocene plays, hydrocarbon zones nature of sediment fill which influenced characteristic have also been identified in Paleocene to Oligocene hydrocarbon generation and entrapment patterns in plays where as in Tapti-Daman sector Daman (Late different sectors, the Basin is subdivided in to a number Oligocene) and Mahuva (Early Oligocene) plays are of blocks, viz. Tapti-Daman block, Diu block, Heera- well established. Panna-Bassein block, Mumbai High-Deep Continental Targeting new objectives in established areas Shelf block, Shelf Margin block and the Ratnagiri and looking for extension of known plays besides block. exploring deeper plays has always been the essence Based on tectonic-sedimentary history and of exploratory activities in Mumbai Offshore Basin.