成烃成藏定量研究及在泌阳凹陷的应用

Application of quantitative examination of petroleum generation and accumulation in Biyang Sag,Nanxiang Basin

石油生成后最初储存在烃源岩(泥质岩)的孔隙空间中,即烃源岩孔隙体积控制烃源岩的生油总量,当石油从烃源岩孔隙体积中排出后,在上覆岩层压实作用下,烃源岩(泥质岩)的孔隙体积将减少排出石油的相应体积,通过计算烃源岩孔隙体积及其变小量可以定量计算烃源岩的生、排油量。上覆岩层的剥蚀,会引起岩层有效上覆压力发生变化,由于砂岩具有弹性特征,有效上覆压力的减小必然会引起砂岩回弹,砂岩回弹增加的孔隙度不仅使地层孔隙流体压力降低,为石油运移提供动力,而且为石油聚集成藏提供了有利的储集空间。此方法在泌阳凹陷的应用表明,核桃园组到廖庄组沉积末为持续沉降加载增压的主要生油期,主要生油层段的生油量和总生油量均在50%以上;廖庄剥蚀期卸载所产生的砂岩回弹量及减压较大的桂岸、双河、侯庄、王集等地区是石油成藏主要有利区。

Petroleum was reserved in pores of source rocks（usually mudstones） after generation.The pore volume of source rock controlled the total amount of hydrocarbon generation.When petroleum had moved out from source rock,the pore volume of source rock decreased due to the compaction of overlying strata,and the decrease amount was equal to the petroleum expelling amount.In this way,we can calculate the total pore volume and the decrease amount so as to find out the generation and expelling amounts of petroleum.If the overlying strata were eroded,sandstones would rebound since pressure had changed.Pore increases resulted from sandstone rebounding caused the decrease of formation fluid pressure,providing both driving force and room for petroleum migration and accumulation.Case studies in the Biyang Sag have indicated that,from Hetaoyuan Formation to the end of Liaozhuang Formation,the sag kept subsiding and pressure increased.Petroleum mainly generated during this stage,accounting for over 50%.The regions such as Guian,Shuanghe,Houzhuang and Wangji are main accumulation locations,where sandstone rebounding amount and pressure decrease resulted from erosions during Liaozhuang stage are bigger.