Relationship between resistivity and saturation of sediments containing highly viscous pore fluids

Abstract

　Subsurface resistivity structure is useful for discussion about distributions and movements of underground fluids; however, the effect by fluid viscosity on the resistivity of strata has not been sufficiently discussed. In this study, we infiltrated highly-viscous mud fluid into sediment samples in the laboratory, then investigated the relationship between mud fluid saturation and the resistivity of sample.

　River-bed sand, mixed with gravel and fine sand, was used in this study. As a result, the mud fluid samples indicate resistive feature at low saturated condition, higher than the samples filled by tap water, and have the larger saturation exponent. Based on qualitative discussion, the behavior of non-Newtonian fluid (Bingham fluid), which restricts the capillarity of mud fluid, seems to be the major cause. It is suggested that pre-survey investigations of characteristics of fluid and the relationship between saturation and resistivity through laboratory experiments are required, when high-viscosity fluid is the survey target.