Resistivity Modeling of Array Laterolog Tools: An Application in an Offshore Norway Clastic Reservoir
Abstract
Resistivity logs, while used extensively in the oil industry for the determination of water-saturation profiles and, consequently, for the quantification of hydrocarbon originally in place (HOIP), are strongly affected by environmental effects such as borehole, shoulder-bed resistivity contrasts, mud-filtrate invasion, dipping beds, and electrical anisotropy. It is well known by log interpreters that the combination of the different effects may strongly affect the estimation of hydrocarbon in place and hydrocarbon reserves. This paper highlights the strong reduction of the uncertainties in water-saturation determination and, consequently, the petrophysical characterization of the reservoir achieved by applying the appropriate 2D resistivity-modeling and -inversion techniques to two wells of the Norwegian offshore area. Both wells were drilled in a sandstone reservoir, with some thin-bedded intervals, and affected by the presence of anomalous invasion profiles.