Bangladesh Offshore Bid and Analysis of Hydrocarbon Potentiality!

 

Offshore Bid and Analysis of Hydrocarbon Potentiality!

The Oil and gas industry is one of the largest sectors in the world business in terms of dollar value, generating an estimated $5.3 trillion in global revenue as of 2024. Oil is crucial to the global economic framework impacting from exploration & production, refining, transportation to heating and electricity to industrial production and manufacturing. Oil & gas is the main catalyst of development and modern civilization. Hydrocarbons make up crude oil and natural gas, which are naturally occurring substances found in rock in the earth's crust. Hydrocarbons are brought to the surface by drilling through the cap rock and into the reservoir.

In 2023, World oil demand growth increase to 1.6mb/d and now lose momentum with 1^st Quarter of 2024 down to 1.2mb/d. With the post-Covid rebound now largely completed and vehicle efficiencies and an expanding EV fleet acting as further drags on oil demand, growth in 2024 and 2025 slows to 1.2mb/d and 1.1mb/d, respectively. 

Bangladesh import fuels included high speed diesel oil, furnace oil, petroleum oil and oils obtained from bituminous minerals, crude etc. In 2023, Bangladesh spent Tk47,261 crore ($4500million) to import 82.66 lakh tons (58million barrel) of crude. Despite the drastic decrease of imports about 10% in 2024, expenditures on imports did not fall due to the increased cost caused by devaluation of the taka against the US dollar. Fuel oil and gas is used for a variety of purposes in Bangladesh, including power generation, fertilizer production and transportation etc. Though large offshore area of Bangladesh is still unexplored, on the other hand Bangladesh is losing huge revenue every year only by importing hydrocarbon. In this circumstances discovery of hydrocarbon in large offshore area can help Bangladesh to get rid of from this huge expenditure and possess Bangladesh into development track.  

Offshore Bangladesh

The Government of the People’s Republic 
of Bangladesh and PetroBangla invite 
International Oil Companies (IOCs) to
bid for acreages for Oil and Gas exploration. 
Nine (9) Shallow Sea blocks (SS-01, 02, 03,
05, 06, 07, 08, 10 & 11) and fifteen (15) 
Deep Sea blocks (DS-08, 09, 10, 11, 12, 
13, 14, 15, 16, 17, 18, 19, 20, 21 & 22)
are currently available for exploration

by the IOCs. 

The Bengal Offshore Basin covers an area of around 120000Km2 or more (!) and has accommodated around 8000 - 10000m of Upper Cretaceous to Recent sediments. The bulk of these sediments were supplied from Ganga- Brahmaputra deltaic system during Mio-Pliocene time. Bengal offshore basin is bounded by other two smaller basin, i.e Offshore Rakhain Basin is located in the South-East of Bengal shelf along Myanmar offshore and Mahanadi offshore basin is located in the South-West of Bengal shelf in the Indian Territory, ranging in water depth from 10m to 2.5Km. All these three basins have remarkable discovery of hydrocarbon which undoubtedly indicate significant hydrocarbon reserve in offshore Bangladesh. 

Offshore Bengal basin could be valuable as of rich organic sources in subsurface rock, generate oil & gas in subsurface and deposited in reservoir rock under prevailing geologic condition, specify offshore is prospective for hydrocarbon. Though there is only very few exploration activities in offshore Bangladesh but have remarkable discovery of gas in offshore and coastal region like Sangu gas field & Kutubdia in offshore, Bhola, Shabajpur and Feni is onshore gas field but close to Coastal border of Offshore.  

In the South-East boundary there is big discovery of gas in Offshore Rakhain basin of Myanmar, i.e. The Shwe natural gas fields consist of three independent gas discoveries, the Shwe, Shwe Phyu and Mya fields. The Shwe fields are in blocks A-1 and A-3 off of Myanmar’s coast. South Korean Oil Company Daewoo is the majority owner and operator of both of these blocks. Myanmar finally signed a contract with China to export 6.5 tcf (trillion cubic feet) of natural gas to China over 30 years.

In the South-West part of Bengal basin along the Indian Territory also have a big discovery of hydrocarbon in offshore Mahanadi basin. India is producing gas from this field and continue more development work.

Above mentioned data clearly shows Bangladesh offshore (shallow & deep) is highly prospective for hydrocarbon. Consequently inviting IOC’s to participate in Bidding and Award of prospective Block through this bidding process, IOC’s could generate revenue by running a profitable business through the course of exploration, drilling & production of hydrocarbon as well as could help Bangladesh Nation.

From geological point Indian plate approached the mainland during Late Cretaceous time, the subsiding area became a typical geo synclinorium that received terrigenous abyssal sediments in the south and flysch sediments in the north. A north-trending island arc developed at the beginning of Tertiary time to the east of Bangladesh. Subsequent to this island arc formation, flysch sedimentation from the north expanded southward. The Indo-Burma Ranges were paroxysm ally elevated during the Oligocene and the east and west flanking basins were compressed and narrowed in succeeding phases up to the present time.

Bangladesh was the site of vast delta buildups during Eocene to Pliocene time. Subsequent Pliocene-Pleistocene alluvial deposits of the Ganges-Brahmaputran Rivers system completely covered the earlier deltaic deposits. These Tertiary strata, below the Pleistocene, have become compressed into long and narrow, north-south oriented folds, produced during the Alpine Orogeny by the westward push of the East Indies island arc. The anticlines have gentle east- and steep west-flanks; thrust faults are numerous. Deformation decreases westward, and in northern Bangladesh the fold and fault pattern becomes more easterly trending.

The late Cretaceous rift led to the development of ponded low in shallow and deep water basins. The lows in deep water are filled with outer neretic to upper bathyal sediments under restrictive environment, entailing better preservation of organic contents. In deep water, the bathyal Late Cretaceous sediments possibly fair to good organic matter richness (TOC 0.5 to 1.47%).

During the Early Paleogene, the Basin experienced passive margin carbonate and finer clastics sedimentation, while during Neogene, it received major fan sediments from Ganga-Brahmputra system. During Paleocene/Eocene time the deep water in southern part were aerially exposed and subtropical paleoclimate was possibly conducive for abundant flora & benthonic fauna (generated in shallow marine). These, deposited in adjoining lows on either side of paleo highs exhibit organic matter richness (TOC 0.23 to 1.73 %).

Eocene sediments, deposited under shallow shelf to fluctuating tidal environment possibly carbonaceous content with fair source rock richness (TOC 0.5 – 5.1%). The possibility of Oligocene shale facies down dip of shelf edge may be a potential source. Neogene reservoir facies deposited as deep water channel fan, slope fan and slope apron in northern part may provide stratigraphic entrapment. Neogene deep water sediments have been deposited as bathyal oozes and turbidity fans. Oozes derived from - planktonic and nektonic organisms, may act as source of hydrocarbon. Distribution of Miocene & Pliocene chaotic facies has been interpreted as possible reservoir rocks.

Further uplift, but no folding of the ranges occurred during early Miocene; at the same time the flanking molasse basins were subsiding. These molasse basins, influenced by the late Miocene and Pliocene terminal folding, were rapidly filled and became areas of terrestrial fluvial sedimentation. Fluvial and deltaic deposition has since continued in the southern seaward regions of the flanking molasse basins of the Ganges delta.

Gas and condensate were generated in the Bengal Basin where the source rocks are marine and non-marine, the temperature gradients are average or slightly lower, and the depth of burial exceeds 2500m to 7000m. Good reservoir and cap-rock-seal conditions developed in shallow marine deltaic environments of deposition during late Eocene through middle Miocene geologic time.

The central and western part of the Bay of Bengal were not affected by compressional folding. The stratigraphic sequence from Oligocene to Holocene represents a deltaic environment of deposition which may range from subaerial delta plain to abyssal marine pro delta.

Most of the hydrocarbons in the world are found in association with geologic basins. Sediments that were deposited in these basins lithified into shale, sandstone and limestone. The juxtaposition of source rock (shale) and potential reservoir rock (sandstone) are of great interest for exploration of oil and gas. As a generalization, the stable or moderately mobile parts of the basin are generally favorable for localization of hydrocarbons.