Bangladesh had its first gas field discovery in Sylhet in 1955. Since then, a total of 27 commercial gas fields have been found in the country with a cumulative original recoverable gas reserve of 28 trillion cubic feet (Tcf), according to Petrobangla official estimates. Commercial production of gas began in 1960 and about 18 Tcf of gas has been produced and consumed by now, leaving a remaining gas reserve of 10 Tcf. Petrobangla estimates a further 1 Tcf of gas in the possible reserve category. On that count, a total of 11 Tcf of gas is reasonably assumed to be in hand for consumption.
On the production side, Bangladesh had seen a steady rise in the local daily gas production rate until mid-2016, when the production level peaked at about 2,750 million cubic feet per day (mmcfd). But since then, the production rate started to decline slowly and steadily, and came down to the level of 2,280 mmcfd by the beginning of May 2021. The chance that local production will rise again is remote to nil in the near future, unless new gas fields are discovered to supplement the known reserves. Gas production is projected to steadily decline in the years to come, and eventually the present reserves will be exhausted at some point. A commonly asked question, therefore, is when the present reserve will run out.
So it’s important to assess when that may happen. Let’s take the Petrobangla data that Bangladesh has a remaining gas reserve of 11 Tcf. The annual supply of local gas has been gradually decreasing from 0.969 Tcf in FY 2017 to 0.961 Tcf in FY 2019, and will decrease further in the coming years, as per Petrobangla data source. It is estimated that the supply from existing reserves will come down to about 0.365 Tcf annually by 2030 and even less by 2035. By 2041, Bangladesh will probably see the last few bubbles of gas from the existing reserves before being depleted completely.
This gas depletion syndrome has swept over the tables of the policymakers. In a quick fix to the problem, import of liquefied natural gas (LNG) has been initiated. Since late 2018, the shortfall of gas supply is being partly compensated through the import of LNG. But LNG is an expensive fuel and costs three times more than the local gas. It is envisaged that LNG will gradually take more and more share of the gas supply in Bangladesh before being the predominant mode of supply in the future. If that happens, the economy will be under pressure, having to live with a large annual LNG import bill in a fund-constrained country. That makes many policymakers uncomfortable as they can foresee a major crisis looming under an unstable energy market.
Interestingly, few people in the corridor of power seem to bother much to ask why the gas reserve scenario has come down to this low—despite the fact that Bangladesh is a very prospective gas province and its gas potential has been highly rated by international and national geoscientists alike. The answer is simple: Bangladesh did not explore enough to bring the “yet to find” gas to the surface and its gas potential remains hidden. Bangladesh remains one of the least explored countries among the prospective gas basins in the world. As a matter of fact, Bangladesh drilled only 28 exploratory wells in the last 20 years, meaning an average drilling rate of a little more than one well per year. This is way too little exploration by any standard. The country consumed about 13 Tcf of gas during the last 20 years, but made new discoveries of less than 2 Tcf of gas.
How much gas may still be hiding beneath the surface in Bangladesh? There have been several assessments of the amount of undiscovered (yet to find) gas in the country by international companies, institutions and joint ventures. Two of the most widely known and accepted assessments are done by the United States Geological Survey (USGS) and the Norwegian Petroleum Directorate (NDP) forming joint ventures with Bangladeshi counterparts. In 2001, a USGS-Petrobangla joint assessment team, after a two-year study, reported that there is a mean (50 percent) probability of finding 32 Tcf of gas resources in the country. In 2002, a Norway-Bangladesh joint venture (NDP-HCU) submitted its assessment report suggesting that the country has a mean (50 percent) probability of finding 41 Tcf of undiscovered gas resources. Prior to these studies, the Shell Oil Company in 1999 suggested a total undiscovered resource potential ranging from 20 to 40 Tcf, with a mean of 32 Tcf. These estimates are based on the geological probability factors responsible for gas occurrences and, therefore, refer to gas resource (that is, still unknown) rather than gas reserve (that is, known).
Where are these gas resources likely to be found? In the explored basins around the world, it has been noticed that as the exploration progresses, there are three stages of success peak. At the initial stage, simple types of gas-oil reserves (like in simple anticline structures) are found and these form the first success peak. A second success peak occurs when the exploration moves to complex reserve types (stratigraphic reserves), and a third success peak occurs as the exploration moves to deep ocean. Bangladesh is yet to cross the first stage, meaning it has not yet completely explored the simple structures. For example, there are still many anticlinal structures in Chittagong Hill Tracts and some of these—like Patya, Sitapahar, and Kasalong—are rated as highly potential for containing gas. As for the second stage, little is done or drilled considering the large area of delta plain land in central and southern Bangladesh, where complex stratigraphic reserves occur abundantly. And finally, the third stage in the deep ocean is totally unknown as not a single well has been drilled in the deep offshore. This is despite the fact that large offshore gas discoveries are made on the other side of the maritime boundaries with both Myanmar and India in the Bay of Bengal.
From the above, it is clear that gas exploration in Bangladesh remains in an immature stage. With so many unexplored areas and potential reserve types, there are high prospects of finding significant new gas reserves. In 2001, a group of people launched a campaign for gas export from Bangladesh and cooked up a theory that Bangladesh is floating on gas. Today, 20 years later, a second group is proposing that gas resources in Bangladesh are about to exhaust, and suggests energy imports as the major source of energy supply. None of the notions—”floating on gas” or “depletion of gas”—have any scientific merit, and are presumably promoted by groups of people with vested interest. A serious exploration drive can certainly offer Bangladesh enough gas to offset the policy of overwhelming dependence on imported energy.
Dr Badrul Imam is Honorary Professor, Department of Geology, University of Dhaka.