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

Many of the concepts used in petrophysics and formation evaluation (FE) were developed for vertical wells, assuming horizontally layered formations. In High Angle/Horizontal wells, the wellbores cut the formations at lower angles and the bed boundary effects become important. FE-log processing with the target to determine “true” formation properties has to consider the local geometry between borehole and formation. To do this, a structural Earth model is required. We developed a semi-automated approach to set up a structural Earth model from geological structures identified on borehole images. A hierarchy is assigned to the structures. Hierarchy and depth or age of the structures identify how these structures truncate each other. This structural Earth model is used for processing formation evaluation logs in HAHZ wells to eliminate the influence of adjacent beds and bed boundaries which are typically more prominent in HAHZ wells than in vertical wells. An example for an almost horizontally layered geological setting is given and the application for a geometrical tool response modeling for a gamma ray log is shown.