An Advanced Ultrahigh-Definition Directional Electromagnetic Propagation Logging Tool for Mapping While Drilling and Multilayered Formation Evaluation
Authors:   Schlumberger, Xie Hui , Sun Keli ,   Schlumberger, Mirto Ettore ,   Schlumberger, Gremillion Joe ,   Schlumberger, Tan Sarwa ,   Schlumberger, Harms Kent ,   Schlumberger, Liu Jianguo ,   Schlumberger, Feng Yao ,   Schlumberger
Published: October 2022

Logging-while-drilling (LWD) electromagnetic (EM) propagation measurements and interpretation techniques have been widely used for reservoir boundary detection in geosteering applications. With more formation information provided near the wellbore during drilling operations, it can still be challenging to obtain an accurate resistivity formation profile in complex scenarios such as multilayered geological structures. This is particularly evident in in high-angle and horizontal (HA/HZ) wells drilled in thin-laminated formations. This paper will present a newly developed LWD mapping-while-drilling service to enable advanced geosteering and formation evaluation in multilayered geological structures. A new electromagnetic multilayer mapping-while-drilling (MLM) tool was designed to measure a complete set of electromagnetic responses in complex formation geometry and anisotropy environment. This tool consists of an industry’s first combination of multi-spaced axial, tilted, and transverse current loop-antennas operating in a multifrequency configuration. The tool measurements are designed so that formation resistivity and geological structure change can be observed directly while drilling. The existing tool offers conventional apparent resistivity, symmetrized, and anti-symmetrized directional measurements. The new tool also provides calibrated deep-resistivity channels acquired from tilted-axial array and anisotropy measurements taken from the transverse antenna. These additional data provide deeper formation measurements and demonstrate stronger sensitivity to anisotropy and bed boundaries. Moreover, the tool also generates real-time high-resolution deep-resistivity images while drilling, which could be beneficial in geosteering. Using these various measurements and a series of state-of-the-art interpretation workflows, a full multilayered formation model can be obtained to show bed boundaries, dipping angle, azimuth, formation resistivity, as well as resistivity anisotropy. Within a 35-ft radius around the wellbore, up to 8 formation layers can be reconstructed. High-definition formation property maps are derived on the curtain-section plot to facilitate operation decisions in complex geosteering environments. Furthermore, a vertical resistivity (Rv) log and a horizontal resistivity (Rh) log can be produced along the well trajectory to display the formation profile for petrophysical evaluation purposes. The interpretation application has been optimized so that the solutions can be provided during drilling operations. Some field data examples will be presented to demonstrate the enhanced mapping and formation evaluation capabilities offered by this new LWD directional electromagnetic propagation tool and interpretation workflow in HA/HZ wells. Compared with the existing tools in the industry, which only show the first boundary near the wellbore most of the time, this recent technology provides significantly more formation layering details, especially in the presence of sedimentary changes or geological discontinuities along the drilling path.