Probe into Quantitative Stratigraphic Interface Evaluation Using a Resistivity Imaging LWD Tool

Resistivity imaging LWD tool can not only visually display the characteristics of micro geological bodies through borehole wall electric imaging, but also can identify the formation interface. In order to explore the logging response mechanism of the tool at the interface, this paper studies the logging response law of the azimuthal resistivity imaging LWD tool at formation interface by using the three-dimensional finite element method. In doing so, it established a quantitative calculation model of formation interface parameters according to the simulation results. The results showed that the resistivity measurement difference of different azimuthal button electrodes of the tool exhibited a good power exponent relationship with the distance from tool to the formation interface in horizontal wells. The angle between the tool and formation interface and the maximum distance between resistivity curve spikes of different azimuthal button electrodes was power exponentially in deviated wells, which is not affected by resistivity contrast of the upper and lower strata at the formation interface. The model for the formation interface parameters interpretation indicated that the tool can be recognized within 1.00 m to the horizontal interface, and the angle can be calculated quantitatively when the angle between the tool and formation interface is less than 20 degrees. The research results can provide a theoretical basis for the application of a resistivity imaging LWD tool in geological engineering.