四川盆地须家河组大气区形成条件

Condition of Xujiahe Formation Large Gas Province Formation in Sichuan Basin

四川盆地须家河组致密天然气的分布具有层系多、面积广、规模大、丰度低,受控于岩性的特点,已经形成了万亿立方米的大气区。是什么因素造成了四川盆地须家河组天然气在如此大范围内叠合连片分布,从而形成大气区。分析认为,烃源岩大面积分布形成广覆式生烃、储集岩大面积不连续分布形成广覆式储烃、盖层的大面积分布形成广覆式封烃以及生储盖层"千层糕"式的广互式组合是形成大气区的基本条件。而烃源岩的连续性生烃造成的持续性供烃,以及构造的稳定性造成的持续性封存是形成大气区的关键因素。烃源层、储集层和盖层在空间上的广互式组合,造成储层和烃源层大面积的直接接触,从而导致油气广复式成藏。这种广复式成藏加之烃源岩的持续性供烃以及持续稳定的保存,最终导致不同层系、不同类型天然气藏在空间上的大面积叠合连片的复式聚集分布,从而形成大气区。

Xujiahe Formation tight gas in the Sichuan basin,which is controlled by lithology distribution,is characterized as wide area,large scale, and low abundance. It has already discovered the trillions of cubic meters large gas province. What are the main control-factors that forming the large gas province.9 Accord ing to exploration practice, the large area distribution of source rocks is prone to form the wide overlap type hydrocarbon generation,the large area discontinuous distribution of reservoir is easy to do the wide overlap type accumulate hydrocarbon,the large area distribution of seal makes the wide overlap type cover hydro carbon,and the mille-feuille style assemblage of source-reservoir-seal constitutes the wide overlap type combination. The key factors to forming large gas province are continuous hydrocarbon generation of source rocks and continuous supplying,and the continuous sealing under the stable structure setting. Wide interbedding type combination of source rock, reservoir and seal causes a large area of direct contact be- tween reservoir and source rocks and wide multiple accumulation of gas. The multiple accumulation as well as source rock continuous supplying and continuous stable save result in the different layers and different types of gas pools to form large area overlapped multiple accumulation distribution, which is formation of large gas provinqe.