低孔隙度低渗透率岩心欠饱和对岩电实验参数的影响分析

岩电实验首先要求用地层水完全饱和岩心.但对于低孔隙度低渗透率岩心,由于受实验周期的限制,岩心往往不能达到完全饱和.岩心欠饱和状态下对地层因素F和电阻增大率I的测量只能是在一定条件下的近似,存在一定误差,误差的绝对值虽然较小,但相对误差却往往较大.通过理论推导、实验验证,说明了岩心欠饱和因素对岩电实验结果中胶结指数m和饱和度指数n的影响,并给出了校正方法.在岩心不能达到完全饱和的情况下,按照正常操作程序实验,对饱和度指数n会产生影响,通常使n值降低,必须增加1个校正值;在岩心无法完全饱和的情况下,按照正常操作程序实验,会对胶结指数m产生明显的影响,且使m值增大,这种影响可以通过引入1个校正量加以校正.

Undersaturation Effects on Electrical Experimental Parameters of Core with Low Porosity and Low Permeability

It is the primary requirement for electrical property experiment of rock that the core sample should be fully saturated with the formation water. However, core samples with low pcrosity and low permeability would not always meet the requirement. The imperfect saturation of the core sample ofien causes rather big relative error in measurement of the formation resistivity factor, F,and the resistivity increscent index, I. Based on theoretical derivation, this paper explains the effect of undersaturation to cementation factor rn and saturation index n deduced from electrical experiment, presents the results of experimental validation, and proposes the correcting method.