Mapping with Auxiliary Data of Varying Accuracy

There are several ways for integrating different sources of data in mapping processes: • Multivariate estimations (cokriging, collocated cokriging) which require the fitting of a multivariate model (variograms and cross-variograms) and a stationary context; • Kriging with external drift or kriging with bayesian drift, which can be applied in non-stationary contexts and requires a univariate model. This paper proposes another approach which is based on the definition of additional data, well distributed over the area of interest, which define upper and lower envelopes for the map to be drawn. These envelopes are built from auxiliary data and will be considered as soft data of less accuracy than hard data. The approach is based on the combination of two geostatistical methods that are quite rarely used, conditional expectation with inequalities and kriging with measurement error. After a brief reminder of the methods, some applications in geological modelling are proposed: * Control of extrapolation * Mapping of geological horizons using the full trace of horizontal wells * Integration of geophysical data of varying accuracy in mapping at regional scale * Mapping layer tops in layer-cake models.