High-frequency induction logging in deviated and horizontal wells: Geosteering and inversion

The study focuses on processing methods for high-frequency induction data from deviated and horizontal wells. Simulation of electromagnetic fields with analytical algorithms is used to study how the resistivity of rocks above and below the well influences the acquired data. The simulations show that the contribution of under- and overlying layers into the recorded responses is considerable and depends on resistivity contrasts between the layers and on the position of logging arrays relative to the layer boundaries. This fact has to be taken into account when estimating true resistivity of reservoirs and when inverting induction logs from horizontal wells for reservoir characterization. The method is applied to oil- and water-saturated reservoirs in West Siberia, which contain high-resistivity impermeable layers leading to overestimation of apparent resistivity. Due regard for the effect of these layers in inversion of induction logs provides high-quality resistivity estimates.