1 barrel (bbl) is 159 litres, by volume.

However,

1 bbl oil equivalent = 140 kg oil equivalent, since average density of oil is about 0.88

• lower than water’s density of 1 and hence oil floats on water
• density varies based on heavier / lighter crude oil, but 0.88 can be taken as the average density for the Indian oil basket.

1 kg oil equivalent leads to 0.04 mmbtu of natural gas

where, mmbtu stands for one Million British thermal unit

Thus, for calculation purposes,

1 bbl oil = 140*0.04 mmbtu = 5.6 mmbtu natural gas

Thus, given the heavy-light crude mix, for the Indian context,

1 barrel oil can be converted to 5.6 mmbtu of gas.