Geology/Petroleum geology of Pakistan
As-salamu alaikum! Why there are so many fields and drilled wells in Kohat-Potwar basin and at Lower Indus Platform Basin and why territory of Central Indus Platform Basin is not explored? It seems to expect all petroleum system elements in this area. Is it depends on political situation in this region?
Walikum assalam Tanzilya
Thanks for sending me this question and please accept my apology for delayed response as I was on annual vacations and I am just able to respond your question now.
Petroleum exploration was initially started in Pakistan near the surface oil seeps near Kundal, Mianwali Punjab in 1866 whereas wells near Khattan, Sibi(Baluchistan) in 1880 found to be producing oil. Khaur was the first commercial and modern day discovery in 1915 which had channelized the systematic exploration throughout the country. Pakistan was part of India before it has taken the presence geographical shape on 14 August 1947 separating from India as an independent country.
First exploration well in Central Indus was drilled by Shell in late 1950ís with an objective to find out the stratigraphy of the area and as I understand they might also be interested to know major reservoirs, source, seal and nature of hydrocarbon and temperature conditions in subsurface. This well has provided treasure of information which proved that basement was not deeper (between 3 to 4 km which were also confirmed by later wells drilled in the region) and major portion of the Phanerozoic sedimentary sequences (Tertiary, Mesozoic and Paleozoic) are present with several major unconformities particularly missing of entire Ordovician to Carboniferous period , almost 200 Million years suggesting that basin has witnessed major inversion and uplift. In present day, tectonically, this area believed to quite passive but presence of unconformities suggests that past was much different.
Although, initially Paleozoic carbonates and sandstone have been targeted but unfortunately these reservoirs were found to be dry .There are only three gas fields have been found as yet ; Nandipur (1984)and Panjpir (1985) and Bahu (2006)gas fields from Cretaceous sandstone reservoirs. This proves that petroleum system indeed exists in this region but probably extent is limited and does not covering the entire basin. Several wells drilled to the basement showed the presence of heavy oil in Precambrian carbonates with very low maturity source rock in Paleozoic whereas other younger sequences have limited source potential. It is possible that localized mature pods of source rocks from Cretaceous or probably deeper source rock likely to exist in the Central Indus which were deposited in paleo grabens which later either inverted or stayed unchanged. Since most of exploration wells are drilled to structural highs where information of source rocks do not always ideal to appreciate with greater precision the basin paleo history and paleo temperature conditions.
Early failures of the exploratory wells have deterred exploration companies to continue explore this otherwise vast area.
Politically, this area is very stable without any local issue but geologically has been yet another puzzle.
For further reading use following link;
Hope, this answer helps.