A novel procedure for geostatistical inversion improved bycombining high-resolution initial guess from travel time inversion

Hydraulic tomography (HT) has been proven as a robust approach to map subsurface heterogeneity through the joint inverse modeling of multiple pumping test data. However, smooth or even erroneous tomograms occur in data sparse areas. In this study, we present a novel procedure of integrating travel time inversion (TTI) results into geostatistical inversion (GI). By treating specific storage (Ss) to be homogeneous, the estimated diffusivity (D) tomogram from TTI is transferred into heterogeneous hydraulic conductivity (K) field. The derived spatial K distribution coupled with effective Ss estimate are utilized as initial guesses for GI. Comparative cases of HT analyses are designed for a numerical case study to highlight the performance of the novel procedure integrated with the TTI result, in which the geostatistical inversion is initialized with: (a) effective homogeneous K and Ss; (2) zonation model results built by different geological information for dividing zones; (3) heterogeneous initial guess of K from the novel procedure. Based on the comparison of lnK and lnSs fields, validation of drawdowns, and examination of travel times indices, results indicate that the novel procedure integrating TTI into HT analysis is demonstrated as an effective approach, which has good performance similar to when a zonation model is integrated with accurate geological information.