3D stochastic inversion of borehole and surface gravity data using Geostatistics

Abstract

), ( ( Summary Geophysical inversion of potential field is impeded because of the intrinsic non-uniqueness of the solution. An inversion method based on a geostati stical approach (cokriging) is presented for threedimensional inversion of gravity borehole and surface data to limit the resulting solution space. Cokriging is a method of estimation that minimizes the error variance by applying cross-correlation between several variables. In this study the estimates are derived using gravity data (from boreholes and the surface) as a secondary variable and the density as the primary variable. The necessary gravity, density and gravity-density covariance matrices are estimated using the observed gravity data. The proposed method is applied to two different synthetic models: 1) a massive orebody; 2) a stochastic distribution of densities. Gravimeters are now becoming available (Gravilog from Scintrex), which can fit boreholes for mineral exploration. Using the borehole data, we can improve the depth resolution of surface inversion. The results show the ability of the method to invert surface and borehole data simultaneously. The results also clearly show the important role of borehole data to improve depth resolution.