SEGJ Technical Conference

Numerical simulation and interpretation of streaming potential anomalies due to the subsurface heterogeneity and infiltration of rain

Abstract We discuss how the spontaneous potential (SP) distribution is quantitatively influenced by subsurface structure and the changes of the groundwater flow, especially the infiltration of rain. The SP distribution can be affected by the subsurface structure such as permeability, coupling co-efficient and resistivity. In addition, the variation of the groundwater flow due to the rainfall could cause SP anomalies. The effects of such factors on the SP distribution, however, have not been discussed quantitatively. In this study, we simulated the groundwater and the generated SP distribution. The changes of groundwater flow due to the heterogeneities of permeability and to the inflow by rain could numerically be estimated in our seepage flow model, and are used to estimate the anomaly in the SP distribution. In addition to the forward simulations, we applied the downward continuation of the simulated SP distributions. The obtained distribution of SP sources is similar to the distribution of sources initially assumed in the forward simulation. The downward continuation could be a useful method for the interpretation in SP analysis.