Petroleum Exploration and Development (Dec 2021)
Sichuan super gas basin in southwest China
Abstract
A sedimentary basin is classified as a super basin when its cumulative production exceeds 5 billion barrels of oil equivalent (6.82×108 t of oil or 7931.66×108 m3 of gas) and its remaining recoverable resources are at least 5 billion barrels of oil equivalent. By the end of 2019, the total output of oil and gas in Sichuan Basin had been 6569×108 m3 with the gas-oil ratio of 80:1, and the total remaining recoverable resources reached 136 404×108 m3, which makes it as a second-tier super basin. Because the output is mainly gas, it is a super gas basin. The reason why the Sichuan Basin is a super gas basin is that it has four advantages: (1) The advantage of gas source rocks: it has the most gas source rocks (9 sets) among all the basins in China. (2) The advantage of resource quantity: it has the most total remaining recoverable resources among all the basins in China (136404×108 m3). (3) The advantage of large gas fields: it has the most large gas fields (27) among all the basins in China. (4) The advantage of total production: by the end of 2019, the total gas production had been 6 487.8×108 m3, which ranked the first among all the basins in China. There are four major breakthroughs in natural gas exploration in Sichuan Basin: (1) A breakthrough in shale gas: shale gas was firstly found in the Ordovician Wufeng-Silurian Longmaxi formations in China. (2) A breakthrough in tight sandstone gas: the Triassic Xu2 Member gas reservoir in Zhongba gas field is the first high recovery tight sandstone gas reservoir in China. (3) A breakthrough in giant carbonate gas fields. (4) A breakthrough in ultra-deep gas reservoir. These breakthroughs have led to important progress in different basins across the country. Super basins are classified according to three criteria: cumulative production and remaining recoverable resources of oil and gas, tectonic attributes of the basin, and the proportions of oil and gas in cumulative oil and gas production.
