Bengal delta is one of the active delta in world and Bangladesh is located within this deltaic region. Every year a huge load of sediment is carried by rivers flowing over Bangladesh and deposited into Bay of Bengal.
The source of petroleum is plants and animals that died millions of years ago and the sediment of Bengal delta carries a huge amount of organic substance which lead to the generation of hydrocarbon through a process of sediment compaction, maturation and migration under certain pressure and temperature within the time span of million years.
Oil and gas prospect in Bangladesh is very potential and have gas discovery through a belt from north east to middle to south eastern and south part of Bangladesh.
Sangu gas field is only offshore discovery is already shut down now. Oil discovery was only at Haripur in Sylhet and not in production track. Oil and gas is only energy that leads the world to modern civilization and show the way of development for a nation.
Bangladesh is still at back on petroleum exploration and could not reach to an expected level of success in the development of country.
Very recent Bangladesh won at the arbitration on International sea territory and opens a vast area for oil and gas exploration in offshore which is highly prospective for hydrocarbon.
Hence Bangladesh Government may anticipate appreciation for their important role on arbitration and cordial gratitude to present government.
Geologically Mio-Pliocene (Time 1.65-23million years) formation is oil and gas bearing formation of Bengal basin and depth ranges from 3.0-5.0km from surface and can be less in deep sea, i.e. 2-3km from sea bed. Sea bed is below water depth and depth ranges 1-1.5km at deep sea.
Deep sea formation is not much affected by the recent deposited sediments as it is far away from depositional arch of shallow sea and hydrocarbon bearing formation will not be deeper at deep sea.
Presence of high pressure in subsurface geology is the main barrier of drilling and very costly drilling as well. Tectonically Bangladesh is located in subduction zone of Indian plate and Burmese plate.
Tectonic feature in formation like major and minor fault, fracture, unconformity etc changes the reservoir of oil and gas as well as represent abnormal pressure indicates the most critical situation for drilling.
Tectonic force is one of the important reason lead discontinuity of rock formation and decompose the reservoir potential of formation.
Need to mention that earthquake is the element of plate movement and it damage not only on the surface but also smash up the rock formation by creating fault and fracture at underground affecting the oil and gas reservoir, migration of hydrocarbon and generate new abnormal pressure zone in formation.
South, south western and western deep sea and nearby area of Bengal basin is likely a trough and consist of organic rich thick sedimentary rock covered by huge water body above sea bed may reduce the consequence of tectonic force to rock body of this area.
Underground drilling hazard will also be less in rock formation of deep sea. Less hazardous formation will be favorable for drilling, may faster the drilling operation and reduce the cost as well for safe completion of drilling a well.
Geologically south, south west and western part of offshore will be more favorable for drilling as the high pressure zone is gradually tend to deeper from north east to south west in formation of this part.
Presence of hydrocarbon at shallow depth in Pleistocene (Time
During drilling Sangu (7) B at Sangu platform observed traces of oil show at shallow depth around 950m-1100m from surface, is not reserve but possibly source.
It suggests have prospect of oil reserve in Pleistocene formation of deep sea. Besides for any discovery of oil and gas it may need to justify reserve quantity and all expenses relate to production stage. So reserve quantity of hydrocarbon is also important for declaration of any oil or gas field.
There is very few offshore drilling in Bangladesh and limited data is not sufficient to analyze oil and gas reserve. So far from the deltaic nature, depositional history and sediment criterion it assumes deep offshore and adjacent area might be rich in oil and gas.
It will not be very surprising if a giant oil field is hiding beneath the deep sea part of Bengal basin. Bangladesh is spending huge foreign currency on importing crude oil and drawing back sustainable development of country.
It is the appropriate time to focus on petroleum exploration in vast offshore area with a great hope of black gold.
Father of the Nation Bangabandhu Sheikh Mujibur Rahman has brought sovereignty for people of Bangladesh and his idolize daughter honorable Prime Minister Sheikh Hasina is very much keen to develop country at each point and working hard to achieve the goal.
Rezaul Kabir is a geologist and an international petroleum exploration specialist.