Water-Cut and Fractional-Flow Logs From Array-Induction Measurements

Abstract

Summary Despite the importance of relative permeabilities in reservoir simulation, no information regarding them is available from current logs. In this paper, for the first time, we demonstrate a continuous log of multiphase flow properties. Mud filtrate invasion is usually regarded as a process that corrupts the true logs. In reality, the multiphase flow characteristics that influence filtrate flow also determine the subsequent reservoir performance. We propose the notion that invasion is an experiment, albeit uncontrolled, that may be used to invert for multiphase flow properties. Thus, in principle, inversion of array induction measurements in terms of the fractional flow curve is possible. The forward model for filtrate invasion is based on two-phase (aqueous and oleic), three-component (oil, water and salt) transport. Hysteretic behavior of relative permeability functions is included. The radial conductivity profiles calculated from the flow model are converted to induction logs using radial response functions. An algorithm for rapid calculations of the forward logs by combining the electromagnetic and flow models is developed. A nonlinear least squares method is used for parameter inversion from measurements. Additional data of near-wellbore resistivity, or logs obtained during drilling, may be included. Presentations for several output logs have been developed: a reserves estimate that partitions porosity into residual and movable saturations, initial water cut in the production stream, the fractional flow curve as a function of saturation, filtrate loss per unit depth, and a quality indicator. A field example of the processing, and its comparison with production data is also discussed.