KARACHI - The country's oil and gas reserves have dropped by 7.6 and 8 percent respectively in 2008 compared to last year as the original recoverable reserves of some key fields were slightly revised down by their respective operators, according to a study report. Major oilfields that witnessed depletion of reserves were Zamzama, Sakhi, Bobi, Jabo, South Mazari, Zaur and Chak- 66 NE fields (representing a cumulative 8.6 percent of the total oil reserves of the country). This is downward revision in their original recoverable reserves, an analytical report revealed. The report added that the downward revision in these fields was partly offset by an upward revision in the Mela field by an approximately 50 percent, which increased its original recoverable reserves to 23.86 million barrels in 2008 from 15.87 million bbl a year earlier, especially since the Mela field represents approximately 6.7 percent of the country's total oil reserves. On a company wise basis, BP's oil reserves fell by 4.3 percent in 2008, which represents approximately 10.4 percent of the total oil reserves of Pakistan. This downward revision was moderately countered by an upward revision of 1.4 percent in Oil and Gas Development Limited's (OGDC) original recoverable reserves, which represent the lion's share of 45 percent of the country's total oil reserves. Amongst the gas fields, which saw downward revisions were the Bahu (-20 percent), Miano (-40 percent), Rehmat (- 42 percent), Chachar (-8 percent) and Sawan (-35 percent) fields. This is approximately 4.5 percent of the total recoverable gas reserves of the country. Moreover, an upward revision of 2 percent in the Uch field from 4.99 tcf to 5.01 tcf slightly offset the fall in reserve numbers from other fields. The Uch field represents approximately 15pc of the country's total recoverable gas reserves. Of the 11 discoveries made in 2008, the reserves of a meager three have been included in the latest figures released by the PPIS, namely Adam (operator -PPL), Missri (BP) and Moolan North (OGDC). It is noteworthy that from previously discovered fields, reserves of three fields were added, namely Zaur West (operator -BP), Ahmed (OPII) and Tando A1lah Yar North (gas -OGDC). Reserve addition of the eight other discoveries should provide a welcome boost to the countries total oil and gas reserves. The report said that Pakistan Petroleum Limited's (PPL) oil and gas reserve lives remain comfortably positioned at 24 and 16 years respectively. Although the addition of Adam field helped in increasing the company's reserves, its high production seems to be having an eroding effect on the company's total gas reserves as no major addition was made to the reserves. The gas Reserve Replacement Ratio (RRR) of the company was at -67 percent in 2008. However, reserves addition from the promising Mami Khel field is expected to improve the company's gas RRR. On the other hand, an upward revision in the oil reserves of Mela field propelled the oil RRR of PPL to 144 percent in 2008. No oil and gas reserve additions were made by Pakistan Oilfield Limited (POL) because of which the company's RRR was recorded at zero percent while its oil and gas reserve lives stand safely at 20 and 41 years respectively. However, POL's high reserve lives stem largely from a low production base, thus undermining its significance. OGDC remains nestled in its position with respective oil and gas reserve lives of 11 and 31 years. Mela's upward revision also boosted OGDC's oil RRR to 14 percent as the company has a 56 percent stake in the field. Gas RRR in 2008 was at 1 percent.