动电效应测井研究现状和展望

Electrokinetic Logging:State of the Art and Future Challenges

在实验室内利用动电效应测量了水饱和岩样的流动电势系数和电渗压力系数,由这些实验系数可计算出渗透率,其值与利用达西定律测量的气渗透率差异很小,不仅说明岩石动电效应可以定量表征,而且可用于测量渗透率;在小型孔隙地层模型井中,观测到了声波诱导的电磁场,也观测到当电偶极子激发瞬变电磁场时诱导的声场;基于声波-电磁耦合方程组,模拟了声诱导电磁场测井响应的全波列和电诱导声场的测井全波列,利用理论波形可对模型井观测现象中的主要部分进行解释。

Great progress has been made in the past twenty years on electrokinetic logging. The Streaming potential and osmotic pressure coefficients of rock samples obtained through laboratory electrokinetic experiments. Permeability is computed from these coefficiencts and compared with the permeability conventionally measured according to the Darcy^s law. From the good agreement between these two permeabilities, it is clear that rock electrokinetic effects can be quantitatively delineated, and can be utilized to measure permeability. The second aspect of progress comes from experiments in scaled boreholes in porous formations. Electric and magnetic signals accomanying acoustic waves are observed when an acoustic monopole transmits waves in the borehole, and inversely, acoustic signals are recorded when an alternating dipole excites electric field. Thirdly, by solving the coupled aocustic and electromagnetic equations under the borehole condition, full waveforms are simulated both for the acousto-electromagntic log and for the elctromagnetic log. Theoretical modeling explained most phenomena observed in laboratory experiments.