ADVANCED UDAR MEASUREMENTS USING TRANSCEIVER CONFIGURATIONS

Measurement interpretation of Ultra-Deep Azimuthal Resistivity (UDAR) has advanced significantly in recent years. Despite these advancements, the need for more data sets is still increasing. Complex geological models require independent and diverse data to best inform the inversion processes used to reconstruct subsurface geology from data. At the same time, additional sensors require length in a bottom hole assembly (BHA), pushing back traditional formation evaluation sensors. Novel ways are required to meet the demand for more data in an efficient manner. This paper introduces a novel transceiver concept that allows creation of rich data sets at the same time optimizing BHA length. A new, modular Logging While Drilling (LWD) UDAR system with tri-axial, collocated orthogonal antennas was designed. Each of the antennas can operate independently as transmitter or receiver. This allows capturing of more diverse data with different transmitterreceiver (TX-RX) spacings for the same BHA configuration. It also allows for the switching of transmitter and receiver positions. The system is studied and compared to a conventional transmitter-receiver system. Synthetic data in forward modeling and inversion is used to visualize and quantify the performance improvements. When switching the transmitter position, one additional intermediate TX-RX spacing can be achieved with a three-module configuration. The increased data set allows for better definition of reservoir structure. This is shown by inversion of synthetic results as well as by computing the resolving power of a specific configuration. Reciprocal measurements serve as quality control for the system. When TX and RX are operated on a single module, shortspacing geosteering measurements are generated. When a module is run close to the bit, these provide deep azimuthal resistivity measurements with a depth of detection (DoD) of up to 10 m, without the need for additional antennas. A standard three module transceiver BHA delivers a data set equivalent to a conventional four module BHA, significantly improving the ability to map the geological structure. A transceiver allows also novel applications of UDAR in a single-module measurement. This measurement delivers shallow geosteering information without compromising the distance to bit for conventional FE measurements. This analysis shows that using a transceiver UDAR system is a key step towards the goal of efficiently creating a comprehensive data set for reservoir mapping.