Structural Earth Modeling as a Basis for Formation Evaluation log Processing in High-Angle/Horizontal Wells

摘要

Many of the concepts used in petrophys-ics and formation evaluation (FE) were developed for scenarios where wells were mostly drilled vertically, cutting horizontally layered formations. So-called "bed boundary effects" occur at the boundary between two different formation layers, where the volume of investigation of the measurement sensor covers both layers. In the case of this simple situation of a vertical well drilling horizontal layers, the significance of the effect depends mostly on the vertical resolution of the measurement sensor and/or configuration. Today, an increasing number of wells are drilled as high angle or horizontal (HAHZ) wells. In this case the well-bore cuts formations at lower angles (higher relative dip) and the bed boundary effects are more severe. The significance of the effect will not only depend on the vertical resolution of the - sensor but also on the angle at which the well-bore cuts the formation. FE-log processing with the target to determine "true" formation properties has to consider the local geometry between the borehole and formation up to several meters from the wellbore to allow for tool response simulation of deep-reading measurements.