The significance of coal-derived gas in major gas producing countries

The core of coal-derived gas theory is that coal measure is the gas source, and the hydrocarbon generation of coal measure is dominated by gas and supplemented by oil, so discoveries in related basins are dominated by gas fields. Discovering and developing giant gas fields, especially those super giant gas fields with recoverable reserves more than 1x10(12) m(3), plays a key role in determining whether a country can be a major gas producing country with annual output over 500x10(8) m(3). The coal resource and coal-derived gas reserves are abundant and widespread in the world, and coal-derived gas makes a major contribution to the gas reserves and gas production in the world. By the end of 2017, 13 super giant coal-derived gas fields have been discovered in the world. The total initial recoverable reserves were 49.995 28x10(12) m(3), accounting for 25.8% of the total remaining recoverable reserves (193.5x10(12) m(3)) in that year in the world. In 2017, there were 15 giant gas producing countries in the world, with a total gas yield of 28 567x10(8) m(3). Among them, six major coal-derived gas producing countries had a total gas yield of 11 369x10(8) m(3), accounting for 39.8% of total gas yield of major gas producing countries. The Urengoi gas field is a super giant coal-derived gas field with the most cumulative gas production in the world. By the end of 2015, the Urengoi gas field had cumulative gas production of 63 043.96x10(8) m(3), with the highest annual gas yield in the world. Its gas output was 3 300x10(8) m(3) in 1989, accounting for 41.4% and 15.7% of the gas output of Russia and the world, respectively. This study introduces the gas source rocks of the basins with super giant coal-derived gas fields in Russia, Turkmenistan, Netherlands, Mozambique and China, and their significances for these countries becoming giant gas producing countries in the world.