新构造运动对中国天然气成藏的控制作用

Control of the Neotectonics in China on Natural Gas Accumulation

由于天然气扩散速率比石油快而不易保存,所以晚期成藏对天然气成藏来说有利于天然气的保存。新构造运动是中国构造史上最后一次大规模的造山运动,对天然气的成藏有着十分重要的控制作用。对于在晚期生气的烃源岩来说,新构造运动产生有效圈闭与晚期供气形成良好匹配,有利于天然气晚期成藏;对于早期成藏的天然气来说,新构造运动使气藏在纵向、横向发生调整,形成新的气藏,另外还可对部分气藏的储层进行优化、改造;新构造运动不仅使圈闭形成,并且还产生断裂系统,沟通烃源岩与储集层,导致幕式成藏,天然气充注效率提高,有利于天然气成藏;另外,新构造运动在构造强烈地区会对已形成的气藏起破坏作用。

Late-stage accumulation of natural gases is beneficial for the preservation of gases for the gases have bigger diffusing capacity than petroleum. The Neotectonic movement is the last event on a large scale in China＇s tectonic evolution history. The movement controlled the natural gas accumulation dramatically. As for source rocks with late hydrocarbon generation, the traps developed by the Newtectonics can well match the late gas generation. This will certainly benefit late gas accumulation. As for early-formed gas pools, the Neotectonics may adjust the gas pools vertically or laterally to form new gas pools. In addition, the Neotectonics can also improve the storage capacity of some reservoirs. The Neotectonic movement not only produces traps, but also causes fractures, which connect the source rock and the reservoir to be a pathway for gas migration. Episodic gas accumulation can easily occur during the Neotectonics, which will bring about high efficiency of gas supply and thus gas pools can be easily formed. Besides, Neotectonics will probably destroy early-formed gas pools in areas of violent tectonics.