中国煤成气地质理论研究进展与重点勘探领域

Research progresses in geological theory and key exploration areas of coal-formed gas in China

通过系统梳理煤成气地质理论的研究进展,分析煤成气对中国天然气储量和产量以及对主要产气盆地天然气勘探的贡献,并综合评价中国煤成气重点的有利勘探区带。取得的主要地质认识如下:①煤系是良好气源岩,生烃以气为主,以油为辅;②建立了基于稳定同位素、轻烃组分、生物标志物为基础的天然气成因鉴别指标体系;③提出了以“生气强度大于20×10^(8)m^(3)/km^(2)”指标为代表的大气田形成的定量/半定量主控因素,为大气田发现指明了方向;④煤成气是中国当前天然气储量和产量的主体,占比均超过55%,支撑塔里木盆地、四川盆地和鄂尔多斯盆地成为中国天然气主力产区;⑤煤岩气是煤成气未来勘探的重大领域,重点区带包括鄂尔多斯盆地乌审旗—米脂地区石炭系本溪组、四川盆地川中—蜀南地区二叠系龙潭组、准噶尔盆地陆梁隆起及南缘侏罗系西山窑组等;⑥煤系致密气是主要的增储上产领域,有利勘探区(带)包括:鄂尔多斯盆地南部和渤海湾盆地石炭系—二叠系致密气、四川盆地川中—川西过渡带三叠系须家河组致密气;⑦准噶尔盆地南缘侏罗系是下一步重要的常规煤成气有利勘探区带。上述研究认识对于进一步发展和完善中国煤成气理论,指导煤成气田勘探具有重要理论和实际意义。

Based on the research progress of the geological theory of coal-formed gas,the contributions of coal-formed gas to the natural gas reserves and production in China and to the development of natural gas in major gas-producing basins are analyzed,and the key favorable exploration zones for coal-formed gas in China are comprehensively evaluated.The following results are obtained.First,coal measures are good gas source rocks,and hydrocarbon generation from coal measure was dominated by gas,followed by oil.Second,a natural gas genetic identification index system based on stable isotopes,light hydrocarbon components,and biomarkers is established.Third,the quantitative and semi-quantitative factors controlling the formation of large gas fields,represented by the indicator of gas generation intensity greater than 20×10^(8) m^(3)/km^(2),are identified to guide the discovery of large gas fields in China.Fourth,coal-formed gas is the major contributor to the current natural gas reserves and production of China,both accounting for over 55%.The high proportion of coal-formed gas has enabled the Tarim,Sichuan and Ordos basins to be the major gas production areas in China.Fifth,coal rock gas is an important field for future exploration of coal-formed gas,and key zones include the Carboniferous Benxi Formation in the Wushenqi-Mizhi area of the Ordos Basin,the Permian Longtan Formation in central-southern Sichuan Basin,the Jurassic Xishanyao Formation in the southern margin and Luliang uplift of the Junggar Basin.Sixth,tight gas is the main area for increasing reserves and production,and the favorable exploration zones include the Carboniferous–Permian in southern Ordos Basin and the Bohai Bay Basin,and the Triassic Xujiahe Formation in the transition zone between central and western Sichuan Basin.Seventh,the Jurassic in the southern margin of the Junggar Basin is a key favorable exploration zone for subsequent investigation of conventional coal-formed gas.These insights have valuable theoretical and practical significance for further developing and improving the theory of coal-formed gas,and guiding the exploration of coal-formed gas fields in China.