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Friday, January 4, 2013

How long will gas last in Bangladesh ?

Photo: Driknews

How long will the estimated gas reserve run" is a question frequently asked. Estimates published in the media show that the gas reserve of the country will be exhausted by 2015, 2017 or 2020. A more realistic assumption may be made by looking into the available data.

Bangladesh produced and consumed about 0.7 Tcf gas in 2011, and the annual gas consumption is likely to increase to about 1 Tcf within three to four years. Assuming an average production and supply rate of about 1 Tcf gas per year, the 16 Tcf of remaining reserve (as of Dec 2011) should run for about 16 years. In other words, Bangladesh is likely to exhaust its gas reserve by about 2025. Is this assumption realistic or overly simplistic?

There are a few points that need to be considered in this regard: i) gas production and supply rate will not remain static over the years, ii) gas production and supply are expected to grow in future, but the growth will not continue, iii) it is expected that the gas production and supply will grow till certain time and then start to decline and the line representing the decline will have a longer tail, and finally, iv) estimated gas reserves may change with time due to reserve addition from reserve growths and new discoveries.

First of all let us discuss what is meant by reserve growth and whether reserve growth of any significance has taken place in any gas field in Bangladesh. Reserve growth refers to the addition to already known reserve in a gas field in the course of field development, i.e. if the boundaries of proven gas areas are extended and/or if new pay zones are found through drilling. Reserve does not grow automatically, but it is the new data acquired through the field development process that led to the increased estimation of the reserve.

Let us take the case of Titas gas field, the largest gas field in Bangladesh, to see if reserve grew over a period of time. In 1991, the initial gas reserve of Titas was estimated by IKM (a Canadian consultant) to be 2.10 Tcf. In 2001, after several more development wells were drilled, the initial reserve of the field was re-estimated by Hydrocarbon Unit of Bangladesh and Norwegian Petroleum Directorate (HCU-NPD) to be 5.13 Tcf, a significant increase from previous estimates. In 2010, with some more development drilling done, the initial gas reserve of Titas field was again estimated by international consultant RPS Energy to be 6.36 Tcf (Petrobala 2012). Therefore Titas gas field is an example where significant reserve growth was documented as the development of the field proceeded over the years.

Now the question is, do all gas fields in Bangladesh registers reserve growth with time like Titas? The answer is certainly not. There are some gas fields which register significant reserve growth while there are some others which do not, and there is a third group which registers negative reserve growth. A negative reserve growth means that the reserve of the field is found to be less than previously estimated.

And finally, how does the total gas reserve of the country play out over the years? In simplistic terms, the reserve of a country gradually declines as gas is produced and consumed. However, this may be compensated by the amount of reserve growth, if any. Even more important is the fact that the reserve may still increase by another factor, i.e. if new reserves are added by new gas field discoveries.

From Petrobangla published data, we may look into how the estimated total gas reserves of the country has changed over the last 20 years taking into account the new gas filed discoveries and reserve growths in the old ones. In 1993, there were 17 gas fields in the country with an estimated total initial gas reserve of 12.43 Tcf and remaining reserves of 10.55 Tcf (Petrobangla 1993). In 2003, the number of gas fields was 22 and the total initial gas reserve was estimated at 20.51 Tcf and a remaining reserve of 15.4 Tcf (Petrobangla 2004). In 2011, the number of gas fields grew to 23 with an estimated initial gas reserve of 26.84 Tcf and a remaining reserve of 16.74 Tcf (Petrobangla 2012). Interestingly, the estimated remaining reserve of the country over the years has not decreased but has increased from 10.55 Tcf in 1993, to 15.4 Tcf in 2003 and to 16.74 Tcf in 2011. This is in spite of the fact that both demand and production of gas have increased over the years.

And now let us consider the main theme of the article, i.e. will Bangladesh exhaust its gas by 2020? Future projections into gas production and supply suggest that gas production will continue to increase for some years now and then it will start to decline. Thereafter, as the above projection shows, the gap between gas demand and supply will continue to widen and will never close. Yet, gas production will continue for considerable amount of time. Let us be more specific on this point.

In 2006, Bangladesh Gas Sector Master Plan was prepared by Petrobangla/World Bank (consultant: Wood Mackenzie) with forecasts of future demand and supply scenarios. In a forecast of gas supply scene from the existing gas fields the production is expected to increase and reach a peak in 2016, and then it will decline. As the demand for gas continues to grow, the gap between demand and supply will continue to widen as the production begins to decline after 2016. Gas production from the existing reserves is expected to continue to 2025 and beyond, although in short supply.

In 2011, Power Sector Master Plan prepared by Japan International Cooperation Agency (JICA), forecast long-term production forecast and set three scenarios -- a high case, a base case and a low case. In each case, in addition to production from existing fields, production from identified new prospects (expected to be added as new fields) are considered. In all three cases, gas production is expected to reach a peak in 2017 and then decline. Taking the base case scenario as reference, production is expected to peak at 3320 mmcfg per day in 2017 and then start to decline (JICA 2011). As the production continues to decline, the gap between demand and supply will continue to widen. However, gas production is expected to continue to 2030 and perhaps beyond, although lesser and lesser in volume over time. According to this projection, gas as a fuel will contribute to 25% of the total electricity generation in 2030 (compared to 88% in 2010) while coal's contribution at that time would be 50% (compared to 4% in 2010).

The above implies that under realistic projection, gas will not be exhausted in Bangladesh by 2020, but is likely to flow till 2030 and perhaps beyond that point.

The writer is, Professor, Geology Department, University of Dhaka.

(References: Energy Resources of Bangladesh, 2nd edition-December 2012, by Badrul Imam published by Bangladesh University Grants Commission, 2012)

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