Hydrocarbon prospect in Deep Offshore of Bangladesh
Hydrocarbon prospect in Deep Offshore
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 & temperature within the time span of million years.
Geologically
Mio-Pliocene (Time 1.65-23million years) formation is oil & 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 water 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 between subduction zone of
Indian plate and Burmese plate. Tectonic feature in formation like major &
minor fault, fracture, unconformity etc changes the reservoir of oil & gas as
well as indicator of abnormal pressure which is most critical barrier of safe 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 not only damage the surface features but also smash up the
rock formation by creating fault & fracture at underground affects oil & gas reservoir, migration of hydrocarbon and generate new abnormal
pressure zone in formation. South, south western and western deep sea &
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 <1.65million years) formation is
prominent in Gulf of Thailand. In Bangladesh offshore have possibility of oil
discovery in Pleistocene formation. 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
& gas it may need to justify reserve quantity and all expenses relate to production
stage. So recoverable quantity and exploration & production cost of hydrocarbon is also important for declaration of
any oil or gas field.
From record very few offshore drilling in Bangladesh and limited data is not sufficient to analyze oil & gas reserve. So far from the deltaic nature, depositional history and sediment criterion it assumes deep offshore & adjacent area might be rich in oil & gas. It will not be very surprising a giant oil reserve is hiding beneath deep sea part of Bengal basin. Bangladesh is spending huge foreign currency on importing crude oil and pulling back sustainable development of country. It is now appropriate time to focus on petroleum exploration in vast offshore area with a great hope of discovery of black gold.
No comments