不同级别渗透率岩心应力敏感实验对比研究

Experimental comparison study on stress sensitivity of different permeability cores

油藏一旦投入开发,原始应力状态发生改变,必然造成油藏岩石发生应力敏感,但是当前争论热点是中高渗储层和低渗储层哪类应力敏感更强。针对这一问题,选取14块直径38mm的天然岩心开展室内实验。为了更好地模拟油藏实际,主要实验设备均置于恒温箱内。根据实验结果分别计算各样品的渗透率损失率,对比分析可知,中高渗岩心的渗透率损失绝对值要比低渗岩心大,但渗透率损失相对值却比低渗岩心小,即低渗油藏具有更强的应力敏感性。以此为基础,归纳了油藏岩石的应力敏感模式,中高渗油藏应力敏感符合"平缓型"模式,低渗透油藏应力敏感符合"先陡后缓型"模式。根据应力敏感模式可知,低渗油藏开发必须控制合理井底流压,避免发生强应力敏感,从而保持油井产能。

The phenomenon of stress sensitivity happens inevitably in the process of recovery in most reservoirs.Whether the stress sensitivity in the mid-high permeability reservoir is stronger than that in the low permeability reservoir is a hot topic currently Aiming at this question,laboratory simulation is conducted.14 samples are selected to test the permeability reduction ratio separately on the indoors simulation experiment,showing that the absolute value of reduction ratio of the mid-high permeability core is higher than that of low permeability core,but the relative permeability reduction ratio is lower than that of low permeability core,which,namely,means the low-permeability reservoir has stronger stress sensitivity.The stress sensitivity curve in high permeability reservoirs could be classified into the type mode of ＂gentle＂,while the stress sensitivity curve in the low permeability reservoir could be the type mode of ＂ slow after steep＂.Hence the bottom-hole flowing pressure must be controlled properly in order to keep the productivity of the well.