Pakistan is blessed with sizeable amounts of natural resources, among which hydrocarbons are very important for national growth and economy. Hydrocarbons are found in certain favourable geological conditions, and are found only in sedimentary basins where Sedimentary Rocks are formed.
In a broad sense, the sedimentary basins are considered the most promising areas for Oil and Gas generation and accumulation. Except few places, most of the areas of Pakistan, including the offshore, are fortunately composed of sedimentary basins (having area more than 800,000 square kilometers compared to total 803,940 square kilometers). Thus, possibilities of finding hydrocarbons have always been high here.
There are two sedimentary basins in Pakistan ie Indus in the east and Balochistan in the west. In addition, two basins also exist in the offshore, Indus offshore and Makran offshore.
THESE MAJOR BASINS OF INDUS AND BALOCHISTAN ARE FURTHER DIVIDED INTO SUB-BASINS:
1. INDUS BASIN
a. Upper Indus Sub-Basin (Kohat and Potwar Area)
b. Middle Indus Sub-Basin (Punjab Plains and Sulaiman Range)
c. Lower Indus Sub-Basin (Sind Plains and Kirthar Range)
2. BALOCHISTAN BASIN
a. Balochistan Sub-Basin
b. Pishin Sub-Basin
3. OFFSHORE
a. Indus off-shore
b. Makran Off-shore
Indus basin is a large basin and the exploration activities in this area date back to pre-independence times. It is very interesting to note that world's first well was drilled in 1859 in Titusville, Pennsylvania USA and the second well drilled in Upper Indus basin of Pakistan at Kundal (near Mianwali) in 1866. However, the first commercial oil discovery was made at Khaur, in Potwar sub basin (Northern Punjab) in 1916 which opened up country's first major oil province in Potwar.
The discovery of gas at Sui, Balochistan in 1952 was another milestone; it also established a gas province in Sulaiman Range and adjoining areas which primarily lie in Balochistan Province. The Sui Field with reserves of 9 trillion cubic feet (TCF) has so far remained the main source of gas supply to country's large consumption market for last three decades.
Mari Field was the second largest gas discovery (1957), with the original recoverable gas reserves of 8.15 TCF. Another significant oil and gas province was added in 1981 in the southern part of the Indus Basin with the discovery of oil at Khaskheli, Badin (Sindh). Lately in 1997, a major gas discovery (of about 1.6 TCF reserves) at Bhit, Kirthar Range, Sindh has established yet another gas province in the country. Nonetheless, in 1998, a major gas discovery at Sawan has proved an entirely new type of play called Stratigraphic play.
The discovery of Chanda (OGDCL), Manzalai & Makori (MOL, a Hungarian oil company) has proved the existence of oil & gas in a previously less interesting area. Similarly, the latest gas discoveries in Zarghun South and Ziarat (near Khost) by Premier Oil and Mari Gas Company Limited (MGCL) at the periphery of Sulaiman Range has opened up a new hydrocarbon play in Indus Basin.
Till to date, only 627 exploratory wells have been drilled in the country resulting in 152 oil and gas discoveries with overall success rate of 1:4, compared to world average of 1:8. The Lukewarm has so far resulted in the discovery of 51 TCF of gas equivalent (Energy Year book 2005), compared to the world's 100 sq Km per well. We can observe the close relationship between numbers of discovered volumes and the rate of drilling activity from (figure-2)
So far, the exploration activities have only been concentrated in Potwar, Lower Indus and Middle Indus/southern Sulaiman Range. Though, there has been some partial/sporadic exploration in Kirthar Range, northern Sulaiman Range and in the newly emerging petroliferous Kohat sub-basin, it was only recently that the exploration attention of E&P companies have been diverted to Kohat sub-basin. Thus, the hydrocarbon potential is yet to be explored/ exploited in this area. The area is still not fully explored even after major discoveries of Chanda, Manzalai, Makori and Mela.
There have also been negligible exploration efforts in Balochistan Basin (including Pishin sub-basin), and offshore areas. Pishin sub-basin has pre-requisites for accumulation of oil & gas. Thus, concerted efforts with sophisticated technology are required to explore/ exploit the hydrocarbon potential of the basin. Southern part of the Indus basin has similar geological characteristics with Bombay area of India, where several, oil & gas discoveries were made.
Indus offshore also requires full attention for exploration, regardless of the lack of investments, induced by previous failures for finding hydrocarbons. MGCL is making serious efforts in harnessing those untapped / undiscovered resources and it has been successful in finding gas in its first well, Ziarat-1, near Khost in Balochistan.
There has been efforts to estimate future potential reserves of Pakistan and a general consensus is that Pakistan holds around 200 Tcf gas or oil equivalent untapped reserves. According to a highly conservative estimate, Pakistani sedimentary basins at least hold untapped reserves of around 41 Tcf of gas or oil equivalent hydrocarbons. (figure-3).
To target the remaining untapped potential of hydrocarbon, seismic coverage and drilling density will have to be increased manifold and huge investments needs to be incurred.
CONCLUSION: Pakistan promises a great future for exploration for oil and gas resources. However, the exploratory activities in the country have so far remained sporadic, cyclic and dependent mainly on the response of foreign oil companies. With improving technology, new possibilities are emerging; for example there has been exploration in Kohat area in recent times compared to Amoco's failure in three wells drilled 12-14 year back.
Amoco seems to have failed primarily because of non availability of present day sophisticated technologies. Whereas now, the latest improvements in seismic technology, availability of high resolution satellite imagery, and advancements in drilling techniques has resulted in recent discoveries of Chanda, Manzalai, Makori and Mela. Similarly Premier Oil & Mari Gas succeeded in finding hydrocarbons near Quetta (at Zarghun and Khost), in a previously unattractive area.
Therefore, there is a strong need for continuity in indigenous research and development efforts in order to re-establish confidence in prospectively of Pakistani sedimentary basins. The local companies need to be encouraged to take the responsibility in the harnessing and in the development of our indigenous resources of energy, thus making our self reliant in our energy needs.
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